Merge pull request #16989 from fabian18/cpu_stm32_add_vbat

cpu/stm32: add backup battery monitoring (VBAT)

boards/common/weact-f4x1cx/include/periph_conf.h

@@ -179,8 +179,10 @@ static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_A, 1), 0, 1},
     {GPIO_PIN(PORT_A, 4), 0, 4},
     {GPIO_PIN(PORT_B, 0), 0, 8},
+    {GPIO_UNDEF, 0, 18} /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(4) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/lora-e5-dev/include/periph_conf.h

@@ -160,8 +160,10 @@ static const i2c_conf_t i2c_config[] = {
 static const adc_conf_t adc_config[] = {
     { GPIO_PIN(PORT_B, 3), 2 },
     { GPIO_PIN(PORT_B, 4), 3 },
+    { GPIO_UNDEF, 14 }, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(2) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/msbiot/include/periph_conf.h

@@ -105,9 +105,11 @@ static const pwm_conf_t pwm_config[] = {
  */
 static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_B, 0), 0, 8},
-    {GPIO_PIN(PORT_B, 1), 0, 9}
+    {GPIO_PIN(PORT_B, 1), 0, 9},
+    {GPIO_UNDEF, 0, 18}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(2) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f031k6/include/periph_conf.h

@@ -122,9 +122,11 @@ static const adc_conf_t adc_config[] = {
     { GPIO_PIN(PORT_A, 1), 1 },
     { GPIO_PIN(PORT_A, 3), 3 },
     { GPIO_PIN(PORT_A, 4), 4 },
-    { GPIO_PIN(PORT_A, 7), 7 }
+    { GPIO_PIN(PORT_A, 7), 7 },
+    { GPIO_UNDEF, 18 }, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(5) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f042k6/include/periph_conf.h

@@ -132,9 +132,11 @@ static const adc_conf_t adc_config[] = {
     { GPIO_PIN(PORT_A, 1), 1 },
     { GPIO_PIN(PORT_A, 3), 3 },
     { GPIO_PIN(PORT_A, 4), 4 },
-    { GPIO_PIN(PORT_A, 7), 7 }
+    { GPIO_PIN(PORT_A, 7), 7 },
+    { GPIO_UNDEF, 18 }, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(5) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f072rb/include/periph_conf.h

@@ -187,9 +187,11 @@ static const adc_conf_t adc_config[] = {
     { GPIO_PIN(PORT_A, 4), 4 },
     { GPIO_PIN(PORT_B, 0), 8 },
     { GPIO_PIN(PORT_C, 1), 11 },
-    { GPIO_PIN(PORT_C, 0), 10 }
+    { GPIO_PIN(PORT_C, 0), 10 },
+    { GPIO_UNDEF, 18 }, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f091rc/include/periph_conf.h

@@ -196,9 +196,11 @@ static const adc_conf_t adc_config[] = {
     { GPIO_PIN(PORT_A, 4), 4 },
     { GPIO_PIN(PORT_B, 0), 8 },
     { GPIO_PIN(PORT_C, 1), 11 },
-    { GPIO_PIN(PORT_C, 0), 10 }
+    { GPIO_PIN(PORT_C, 0), 10 },
+    { GPIO_UNDEF, 18 }, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f207zg/include/periph_conf.h

@@ -236,9 +236,11 @@ static const spi_conf_t spi_config[] = {
  */
 static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_A, 3), 0, 3},
-    {GPIO_PIN(PORT_C, 0), 1, 0}
+    {GPIO_PIN(PORT_C, 0), 1, 0},
+    {GPIO_UNDEF, 0, 18}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(2) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f302r8/include/periph_conf.h

@@ -47,7 +47,7 @@ extern "C" {
  * Note that we do not configure all ADC channels,
  * and not in the STM32F302 order.  Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -58,8 +58,10 @@ static const adc_conf_t adc_config[] = {
     { .pin = GPIO_PIN(PORT_B, 0), .dev = 0, .chan = 11 }, /* ADC_IN11, slow */
     { .pin = GPIO_PIN(PORT_C, 1), .dev = 0, .chan =  7 }, /* ADC_IN7,  slow */
     { .pin = GPIO_PIN(PORT_C, 0), .dev = 0, .chan =  6 }, /* ADC_IN6,  slow */
+    { .pin = GPIO_UNDEF, .dev = 0, .chan = 17 }, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f303k8/include/periph_conf.h

@@ -33,7 +33,7 @@ extern "C" {
  * Note that we do not configure all ADC channels,
  * and not in the STM32F303 order.  Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A3 and A6
+ * Arduino header pins A0-A3 and A6 and the internal VBAT channel.
  *
  * @{
  */
@@ -43,8 +43,10 @@ static const adc_conf_t adc_config[] = {
     { .pin = GPIO_PIN(PORT_A, 3), .dev = 0, .chan = 4 }, /* ADC1_IN4, fast */
     { .pin = GPIO_PIN(PORT_A, 4), .dev = 1, .chan = 1 }, /* ADC2_IN1, fast */
     { .pin = GPIO_PIN(PORT_A, 7), .dev = 1, .chan = 4 }, /* ADC2_IN4, fast */
+    { .pin = GPIO_UNDEF, .dev = 0, .chan = 17 }, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(5) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f303re/include/periph_conf.h

@@ -45,7 +45,7 @@ extern "C" {
  * Note that we do not configure all ADC channels,
  * and not in the STM32F334 order.  Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -56,8 +56,10 @@ static const adc_conf_t adc_config[] = {
     { .pin = GPIO_PIN(PORT_B, 0), .dev = 2, .chan = 12 }, /* ADC3_IN12, slow */
     { .pin = GPIO_PIN(PORT_C, 1), .dev = 1, .chan =  7 }, /* ADC12_IN7, slow */
     { .pin = GPIO_PIN(PORT_C, 0), .dev = 1, .chan =  6 }, /* ADC12_IN6, slow */
+    { .pin = GPIO_UNDEF, .dev = 0, .chan = 17 }, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f303ze/include/periph_conf.h

@@ -43,7 +43,7 @@ extern "C" {
  * Note that we do not configure all ADC channels,
  * and not in the STM32F303 order.  Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -53,9 +53,11 @@ static const adc_conf_t adc_config[] = {
     { .pin = GPIO_PIN(PORT_C,  3), .dev = 1, .chan =  9 }, /* ADC12_IN9, slow */
     { .pin = GPIO_PIN(PORT_D, 11), .dev = 2, .chan =  8 }, /* ADC34_IN8, slow */
     { .pin = GPIO_PIN(PORT_D, 12), .dev = 3, .chan =  9 }, /* ADC34_IN9, slow */
-    { .pin = GPIO_PIN(PORT_D, 13), .dev = 3, .chan = 10 }, /* ADC34_IN10, slo */
+    { .pin = GPIO_PIN(PORT_D, 13), .dev = 3, .chan = 10 }, /* ADC34_IN10, slow */
+    { .pin = GPIO_UNDEF, .dev = 0, .chan = 17 }, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f334r8/include/periph_conf.h

@@ -44,7 +44,7 @@ extern "C" {
  * Note that we do not configure all ADC channels,
  * and not in the STM32F334 order.  Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -55,8 +55,10 @@ static const adc_conf_t adc_config[] = {
     { .pin = GPIO_PIN(PORT_B, 0), .dev = 0, .chan = 11 }, /* ADC1_IN11, slow */
     { .pin = GPIO_PIN(PORT_C, 1), .dev = 1, .chan =  7 }, /* ADC12_IN7, slow */
     { .pin = GPIO_PIN(PORT_C, 0), .dev = 1, .chan =  6 }, /* ADC12_IN6, slow */
+    { .pin = GPIO_UNDEF, .dev = 0, .chan = 17 }, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f401re/include/periph_conf.h

@@ -243,7 +243,7 @@ static const spi_conf_t spi_config[] = {
  * Note that we do not configure all ADC channels,
  * and not in the STM32F401 order.  Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -254,8 +254,10 @@ static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_B, 0), 0, 8},
     {GPIO_PIN(PORT_C, 1), 0, 11},
     {GPIO_PIN(PORT_C, 0), 0, 10},
+    {GPIO_UNDEF, 0, 18}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f410rb/include/periph_conf.h

@@ -146,7 +146,7 @@ static const spi_conf_t spi_config[] = {
  * Note that we do not configure all ADC channels,
  * and not in the STM32F410 order.  Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -157,8 +157,10 @@ static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_B, 0), 0, 8},
     {GPIO_PIN(PORT_C, 1), 0, 11},
     {GPIO_PIN(PORT_C, 0), 0, 10},
+    {GPIO_UNDEF, 0, 18}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f411re/include/periph_conf.h

@@ -175,7 +175,7 @@ static const spi_conf_t spi_config[] = {
  * Note that we do not configure all ADC channels,
  * and not in the STM32F411 order.  Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -186,8 +186,10 @@ static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_B, 0), 0, 8},
     {GPIO_PIN(PORT_C, 1), 0, 11},
     {GPIO_PIN(PORT_C, 0), 0, 10},
+    {GPIO_UNDEF, 0, 18}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f412zg/include/periph_conf.h

@@ -177,7 +177,7 @@ static const spi_conf_t spi_config[] = {
  * Note that we do not configure all ADC channels,
  * and not in the STM32F412zg order. Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -188,8 +188,10 @@ static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_C, 1), 0, 11},
     {GPIO_PIN(PORT_C, 4), 0, 14},
     {GPIO_PIN(PORT_C, 5), 0, 15},
+    {GPIO_UNDEF, 0, 18}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f413zh/include/periph_conf.h

@@ -178,7 +178,7 @@ static const spi_conf_t spi_config[] = {
  * Note that we do not configure all ADC channels,
  * and not in the STM32F413zh order. Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -189,8 +189,10 @@ static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_C, 1), 0, 11},
     {GPIO_PIN(PORT_C, 4), 0, 14},
     {GPIO_PIN(PORT_C, 5), 0, 15},
+    {GPIO_UNDEF, 0, 18}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f429zi/include/periph_conf.h

@@ -175,7 +175,7 @@ static const spi_conf_t spi_config[] = {
  * Note that we do not configure all ADC channels,
  * and not in the STM32F429zi order. Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -186,8 +186,10 @@ static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_F, 3), 2, 9},
     {GPIO_PIN(PORT_F, 5), 2, 15},
     {GPIO_PIN(PORT_F, 10), 2, 8},
+    {GPIO_UNDEF, 0, 18}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f446re/include/periph_conf.h

@@ -253,7 +253,7 @@ static const spi_conf_t spi_config[] = {
  * Note that we do not configure all ADC channels,
  * and not in the STM32F446 order.  Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -264,8 +264,10 @@ static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_B, 0), 0, 8},
     {GPIO_PIN(PORT_C, 1), 0, 11},
     {GPIO_PIN(PORT_C, 0), 0, 10},
+    {GPIO_UNDEF, 0, 18}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-f767zi/include/periph_conf.h

@@ -193,7 +193,7 @@ static const eth_conf_t eth_config = {
  * Note that we do not configure all ADC channels,
  * and not in the STM32F767ZI order.  Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -204,8 +204,10 @@ static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_F, 3), 2, 9},
     {GPIO_PIN(PORT_F, 5), 2, 15},
     {GPIO_PIN(PORT_F, 10), 2, 8},
+    {GPIO_UNDEF, 0, 18}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-g070rb/include/periph_conf.h

@@ -92,7 +92,7 @@ static const uart_conf_t uart_config[] = {
  * Note that we do not configure all ADC channels,
  * and not in the STM32G070 order.  Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -103,8 +103,10 @@ static const adc_conf_t adc_config[] = {
     { .pin = GPIO_PIN(PORT_B,  1), .dev = 0, .chan =  9 },
     { .pin = GPIO_PIN(PORT_B, 11), .dev = 0, .chan = 15 },
     { .pin = GPIO_PIN(PORT_B, 12), .dev = 0, .chan = 16 },
+    { .pin = GPIO_UNDEF, .dev = 0, .chan = 14}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-g071rb/include/periph_conf.h

@@ -90,7 +90,7 @@ static const uart_conf_t uart_config[] = {
  * Note that we do not configure all ADC channels,
  * and not in the STM32G071 order.  Instead, we
  * just define 6 ADC channels, for the Nucleo
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -101,8 +101,10 @@ static const adc_conf_t adc_config[] = {
     { .pin = GPIO_PIN(PORT_B,  1), .dev = 0, .chan =  9 },
     { .pin = GPIO_PIN(PORT_B, 11), .dev = 0, .chan = 15 },
     { .pin = GPIO_PIN(PORT_B, 12), .dev = 0, .chan = 16 },
+    { .pin = GPIO_UNDEF, .dev = 0, .chan = 14}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/nucleo-l476rg/include/periph_conf.h

@@ -210,6 +210,7 @@ static const spi_conf_t spi_config[] = {
  * @name    ADC configuration
  *
  * configure only  ADC channels for the Arduino header pins A0-A5
+ * and the internal VBAT channel
  *
  * @{
  */
@@ -220,8 +221,10 @@ static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_B, 0), 1, 15}, /*< ADC12_IN15 */
     {GPIO_PIN(PORT_C, 1), 2, 2},  /*< ADC123_IN_2 */
     {GPIO_PIN(PORT_C, 0), 2, 1},  /*< ADC123_IN_1 */
+    {GPIO_UNDEF, 0, 18}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/stm32f0discovery/include/periph_conf.h

@@ -96,9 +96,11 @@ static const adc_conf_t adc_config[] = {
     { GPIO_PIN(PORT_C, 2), 12 },
     { GPIO_PIN(PORT_C, 3), 13 },
     { GPIO_PIN(PORT_C, 4), 14 },
-    { GPIO_PIN(PORT_C, 5), 15 }
+    { GPIO_PIN(PORT_C, 5), 15 },
+    { GPIO_UNDEF, 18 }, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/stm32f469i-disco/include/periph_conf.h

@@ -227,7 +227,7 @@ static const pwm_conf_t pwm_config[] = {
  * @name ADC configuration
  *
  * Not all ADCs are configured, by now, only the 6 ones available
- * on the Arduino(R) connector A0-A5
+ * on the Arduino(R) connector A0-A5 and internal VBAT ADC channel.
  * @{
  */
 static const adc_conf_t adc_config[] = {
@@ -237,7 +237,10 @@ static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_C, 4), 2, 14},
     {GPIO_PIN(PORT_C, 5), 2, 15},
     {GPIO_PIN(PORT_A, 4), 2, 4},
+    {GPIO_UNDEF, 0, 18}, /* VBAT */
 };
+
+#define VBAT_ADC    ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF   ARRAY_SIZE(adc_config)
 /** @} */
 

boards/stm32f4discovery/include/periph_conf.h

@@ -131,9 +131,11 @@ static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_A, 1), 0, 1},
     {GPIO_PIN(PORT_A, 4), 0, 4},
     {GPIO_PIN(PORT_C, 1), 1, 11},
-    {GPIO_PIN(PORT_C, 2), 1, 12}
+    {GPIO_PIN(PORT_C, 2), 1, 12},
+    {GPIO_UNDEF, 0, 18}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(4) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

boards/ublox-c030-u201/include/periph_conf.h

@@ -222,7 +222,7 @@ static const i2c_conf_t i2c_config[] = {
  * Note that we do not configure all ADC channels,
  * and not in the STM32F437 order.  Instead, we
  * just define 6 ADC channels, for the
- * Arduino header pins A0-A5
+ * Arduino header pins A0-A5 and the internal VBAT channel.
  *
  * @{
  */
@@ -233,8 +233,10 @@ static const adc_conf_t adc_config[] = {
     {GPIO_PIN(PORT_A, 4), 0, 14},
     {GPIO_PIN(PORT_B, 7), 0, 7},
     {GPIO_PIN(PORT_B, 6), 0, 6},
+    {GPIO_UNDEF, 0, 18}, /* VBAT */
 };
 
+#define VBAT_ADC            ADC_LINE(6) /**< VBAT ADC line */
 #define ADC_NUMOF           ARRAY_SIZE(adc_config)
 /** @} */
 

cpu/stm32/Makefile.dep

@@ -49,5 +49,8 @@ ifneq (,$(filter periph_adc,$(FEATURES_USED)))
   endif
 endif
 
+ifneq (,$(filter periph_vbat,$(USEMODULE)))
+  FEATURES_REQUIRED += periph_adc
+endif
 
 include $(RIOTCPU)/cortexm_common/Makefile.dep

cpu/stm32/Makefile.features

@@ -34,6 +34,25 @@ ifneq (,$(filter $(STM32_WITH_BKPRAM),$(CPU_MODEL)))
   FEATURES_PROVIDED += backup_ram
 endif
 
+STM32_WITH_VBAT = stm32f031% stm32f038% stm32f042% stm32f048% \
+                  stm32f051% stm32f058% stm32f071% stm32f072% \
+                  stm32f078% stm32f091% stm32f098% \
+                  stm32f2% \
+                  stm32f3% \
+                  stm32f4% \
+                  stm32f7% \
+                  stm32g0% \
+                  stm32g4% stm32gbk1cb \
+                  stm32l4% \
+                  stm32l5% \
+                  stm32u5% \
+                  stm32wb% \
+                  stm32wl%
+
+ifneq (,$(filter $(STM32_WITH_VBAT),$(CPU_MODEL)))
+  FEATURES_PROVIDED += periph_vbat
+endif
+
 # The f2, f4 and f7 do not support the pagewise api
 ifneq (,$(filter $(CPU_FAM),f2 f4 f7))
   FEATURES_PROVIDED += periph_flashpage

cpu/stm32/cpu_init.c

@@ -38,6 +38,7 @@
 #include "periph_cpu.h"
 #include "periph/init.h"
 #include "periph/gpio.h"
+#include "periph/vbat.h"
 #include "board.h"
 #include "pm_layered.h"
 
@@ -395,14 +396,29 @@ void backup_ram_init(void)
 #define BACKUP_RAM_MAGIC    {'R', 'I', 'O', 'T'}
 #endif
 
-bool cpu_woke_from_backup(void)
+static inline bool _backup_battery_connected(void) {
-{
+#if IS_USED(MODULE_PERIPH_VBAT)
+    vbat_init(); /* early use of VBAT requires init() */
+    return !vbat_is_empty();
+#endif
+    return false;
+}
+
+bool cpu_woke_from_backup(void) {
 #if IS_ACTIVE(CPU_HAS_BACKUP_RAM)
     static const char _signature[] BACKUP_RAM_DATA = BACKUP_RAM_MAGIC;
-    /* switch off regulator to save power */
+    if (_backup_battery_connected()) {
+        /* in case the board has a backup battery the regulator must be on
+        to mitigate (unexpected) outage of VDD, so RTC register and
+        backup domain register contents are not lost */
+        pm_backup_regulator_on();
+    }
+    else {
 #ifndef RIOTBOOT
-    pm_backup_regulator_off();
+        /* switch off regulator to save power */
+        pm_backup_regulator_off();
 #endif
+    }
     for (unsigned i = 0; i < sizeof(_signature); i++) {
         if (_signature[i] != ((char[])BACKUP_RAM_MAGIC)[i]) {
             return false;

cpu/stm32/include/periph/cpu_vbat.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2022 Otto-von-Guericke-Universität Magdeburg
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup         cpu_stm32
+ * @{
+ *
+ * @file
+ * @brief           CPU internal VBAT interface and definitions of the STM32 family
+ *
+ * @author          Fabian Hüßler <fabian.huessler@ovgu.de>
+ */
+
+#ifndef PERIPH_CPU_VBAT_H
+#define PERIPH_CPU_VBAT_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   Enable the VBAT sampling channel
+ */
+void vbat_enable(void);
+
+/**
+ * @brief   Disable the VBAT sampling channel
+ */
+void vbat_disable(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* PERIPH_CPU_VBAT_H */
+/** @} */

cpu/stm32/include/periph/f0/periph_cpu.h

@@ -61,6 +61,15 @@ typedef enum {
     ADC_RES_16BIT = (0xff)          /**< not applicable */
 } adc_res_t;
 /** @} */
+
+/**
+ * @name   Constants for internal VBAT ADC line
+ * @{
+ */
+#define VBAT_ADC_RES        ADC_RES_12BIT
+#define VBAT_ADC_MAX        4095
+/** @} */
+
 #endif /* ndef DOXYGEN */
 
 #ifdef __cplusplus

cpu/stm32/include/periph/f2/periph_cpu.h

@@ -58,6 +58,15 @@ typedef enum {
     ADC_RES_16BIT = 2            /**< ADC resolution: 16 bit (not supported)*/
 } adc_res_t;
 /** @} */
+
+/**
+ * @name   Constants for internal VBAT ADC line
+ * @{
+ */
+#define VBAT_ADC_RES        ADC_RES_12BIT
+#define VBAT_ADC_MAX        4095
+/** @} */
+
 #endif /* ndef DOXYGEN */
 
 #ifdef __cplusplus

cpu/stm32/include/periph/f3/periph_cpu.h

@@ -69,6 +69,15 @@ typedef enum {
     ADC_RES_16BIT = (0x2)             /**< not applicable */
 } adc_res_t;
 /** @} */
+
+/**
+ * @name   Constants for internal VBAT ADC line
+ * @{
+ */
+#define VBAT_ADC_RES        ADC_RES_12BIT
+#define VBAT_ADC_MAX        4095
+/** @} */
+
 #endif /* ndef DOXYGEN */
 
 #ifdef __cplusplus

cpu/stm32/include/periph/f4/periph_cpu.h

@@ -69,6 +69,15 @@ typedef enum {
     ADC_RES_16BIT = 2               /**< ADC resolution: 16 bit (not supported)*/
 } adc_res_t;
 /** @} */
+
+/**
+ * @name   Constants for internal VBAT ADC line
+ * @{
+ */
+#define VBAT_ADC_RES        ADC_RES_12BIT
+#define VBAT_ADC_MAX        4095
+/** @} */
+
 #endif /* ndef DOXYGEN */
 
 #ifdef __cplusplus

cpu/stm32/include/periph/f7/periph_cpu.h

@@ -52,6 +52,15 @@ typedef enum {
     ADC_RES_16BIT = 2               /**< ADC resolution: 16 bit (not supported)*/
 } adc_res_t;
 /** @} */
+
+/**
+ * @name   Constants for internal VBAT ADC line
+ * @{
+ */
+#define VBAT_ADC_RES        ADC_RES_12BIT
+#define VBAT_ADC_MAX        4095
+/** @} */
+
 #endif /* ndef DOXYGEN */
 
 #ifdef __cplusplus

cpu/stm32/include/periph/g0/periph_cpu.h

@@ -32,6 +32,14 @@ extern "C" {
  */
 #define STM32_BOOTLOADER_ADDR   (0x1FFF0000)
 
+/**
+ * @name   Constants for internal VBAT ADC line
+ * @{
+ */
+#define VBAT_ADC_RES        ADC_RES_12BIT
+#define VBAT_ADC_MAX        4095
+/** @} */
+
 #endif /* ndef DOXYGEN */
 
 /**

cpu/stm32/include/periph/g4/periph_cpu.h

@@ -32,6 +32,14 @@ extern "C" {
  */
 #define STM32_BOOTLOADER_ADDR   (0x1FFF0000)
 
+/**
+ * @name   Constants for internal VBAT ADC line
+ * @{
+ */
+#define VBAT_ADC_RES        ADC_RES_12BIT
+#define VBAT_ADC_MAX        4095
+/** @} */
+
 #endif /* ndef DOXYGEN */
 
 #ifdef __cplusplus

cpu/stm32/include/periph/l4/periph_cpu.h

@@ -63,6 +63,15 @@ typedef enum {
     ADC_RES_16BIT = (0x2)             /**< not applicable */
 } adc_res_t;
 /** @} */
+
+/**
+ * @name   Constants for internal VBAT ADC line
+ * @{
+ */
+#define VBAT_ADC_RES        ADC_RES_12BIT
+#define VBAT_ADC_MAX        4095
+/** @} */
+
 #endif /* ndef DOXYGEN */
 
 #ifdef __cplusplus

cpu/stm32/include/periph/l5/periph_cpu.h

@@ -32,6 +32,14 @@ extern "C" {
  */
 #define STM32_BOOTLOADER_ADDR   (0x0BF90000)
 
+/**
+ * @name   Constants for internal VBAT ADC line
+ * @{
+ */
+#define VBAT_ADC_RES        ADC_RES_12BIT
+#define VBAT_ADC_MAX        4095
+/** @} */
+
 #endif /* ndef DOXYGEN */
 
 #ifdef __cplusplus

cpu/stm32/include/periph/u5/periph_cpu.h

@@ -32,6 +32,14 @@ extern "C" {
  */
 #define STM32_BOOTLOADER_ADDR   (0x0BF90000)
 
+/**
+ * @name   Constants for internal VBAT ADC line
+ * @{
+ */
+#define VBAT_ADC_RES        ADC_RES_14BIT
+#define VBAT_ADC_MAX        16383
+/** @} */
+
 #endif /* ndef DOXYGEN */
 
 #ifdef __cplusplus

cpu/stm32/include/periph/wb/periph_cpu.h

@@ -32,6 +32,14 @@ extern "C" {
  */
 #define STM32_BOOTLOADER_ADDR   (0x1FFF0000)
 
+/**
+ * @name   Constants for internal VBAT ADC line
+ * @{
+ */
+#define VBAT_ADC_RES        ADC_RES_12BIT
+#define VBAT_ADC_MAX        4095
+/** @} */
+
 #endif /* ndef DOXYGEN */
 
 #ifdef __cplusplus

cpu/stm32/include/periph/wl/periph_cpu.h

@@ -57,6 +57,14 @@ typedef enum {
  */
 #define STM32_BOOTLOADER_ADDR   (0x1FFF0000)
 
+/**
+ * @name   Constants for internal VBAT ADC line
+ * @{
+ */
+#define VBAT_ADC_RES        ADC_RES_12BIT
+#define VBAT_ADC_MAX        4095
+/** @} */
+
 #endif /* ndef DOXYGEN */
 
 /**

cpu/stm32/include/periph_cpu.h

@@ -72,6 +72,7 @@
 #include "periph/cpu_timer.h"
 #include "periph/cpu_uart.h"
 #include "periph/cpu_usbdev.h"
+#include "periph/cpu_vbat.h"
 #include "periph/cpu_wdt.h"
 
 #ifdef MODULE_PERIPH_CAN

cpu/stm32/kconfigs/f0/Kconfig.lines

@@ -27,33 +27,39 @@ config CPU_LINE_STM32F031X6
     bool
     select CPU_FAM_F0
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
 
 config CPU_LINE_STM32F038XX
     bool
     select CPU_FAM_F0
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
 
 config CPU_LINE_STM32F042X6
     bool
     select CPU_FAM_F0
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
 
 config CPU_LINE_STM32F048XX
     bool
     select CPU_FAM_F0
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
 
 config CPU_LINE_STM32F051X8
     bool
     select CPU_FAM_F0
     select CLOCK_HAS_NO_MCO_PRE
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
 
 config CPU_LINE_STM32F058XX
     bool
     select CPU_FAM_F0
     select CLOCK_HAS_NO_MCO_PRE
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
 
 config CPU_LINE_STM32F070X6
     bool
@@ -67,23 +73,28 @@ config CPU_LINE_STM32F071XB
     bool
     select CPU_FAM_F0
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
 
 config CPU_LINE_STM32F072XB
     bool
     select CPU_FAM_F0
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
 
 config CPU_LINE_STM32F078XX
     bool
     select CPU_FAM_F0
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
 
 config CPU_LINE_STM32F091XC
     bool
     select CPU_FAM_F0
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
 
 config CPU_LINE_STM32F098XX
     bool
     select CPU_FAM_F0
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT

cpu/stm32/kconfigs/f2/Kconfig

@@ -15,6 +15,7 @@ config CPU_FAM_F2
     select HAS_PERIPH_FLASHPAGE
     select HAS_PERIPH_HWRNG
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
     select HAS_PERIPH_WDT
     select HAS_BOOTLOADER_STM32
 

cpu/stm32/kconfigs/f3/Kconfig

@@ -14,6 +14,7 @@ config CPU_FAM_F3
     select HAS_PERIPH_FLASHPAGE_PAGEWISE
     select HAS_PERIPH_FLASHPAGE_RAW
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
     select HAS_PERIPH_WDT
     select HAS_BOOTLOADER_STM32
 

cpu/stm32/kconfigs/f4/Kconfig

@@ -13,6 +13,7 @@ config CPU_FAM_F4
     select HAS_CORTEXM_MPU
     select HAS_PERIPH_FLASHPAGE
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
     select HAS_PERIPH_WDT
     select HAS_BOOTLOADER_STM32
 

cpu/stm32/kconfigs/f7/Kconfig

@@ -15,6 +15,7 @@ config CPU_FAM_F7
     select HAS_PERIPH_FLASHPAGE
     select HAS_PERIPH_HWRNG
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
     select HAS_PERIPH_WDT
     select HAS_BOOTLOADER_STM32
 

cpu/stm32/kconfigs/g0/Kconfig

@@ -13,6 +13,7 @@ config CPU_FAM_G0
     select HAS_PERIPH_FLASHPAGE
     select HAS_PERIPH_FLASHPAGE_PAGEWISE
     select HAS_PERIPH_FLASHPAGE_RAW
+    select HAS_PERIPH_VBAT
     select HAS_PERIPH_WDT
     select HAS_BOOTLOADER_STM32
 

cpu/stm32/kconfigs/g4/Kconfig

@@ -14,6 +14,7 @@ config CPU_FAM_G4
     select HAS_PERIPH_FLASHPAGE
     select HAS_PERIPH_FLASHPAGE_PAGEWISE
     select HAS_PERIPH_HWRNG
+    select HAS_PERIPH_VBAT
     select HAS_PERIPH_WDT
     select HAS_BOOTLOADER_STM32
 

cpu/stm32/kconfigs/l4/Kconfig

@@ -15,6 +15,7 @@ config CPU_FAM_L4
     select HAS_PERIPH_FLASHPAGE_PAGEWISE
     select HAS_PERIPH_HWRNG
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
     select HAS_PERIPH_WDT
     select HAS_BOOTLOADER_STM32
 

cpu/stm32/kconfigs/l5/Kconfig

@@ -14,6 +14,7 @@ config CPU_FAM_L5
     select HAS_PERIPH_FLASHPAGE_PAGEWISE
     select HAS_PERIPH_HWRNG
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
     select HAS_PERIPH_WDT
     select HAS_BOOTLOADER_STM32
 

cpu/stm32/kconfigs/u5/Kconfig

@@ -15,6 +15,7 @@ config CPU_FAM_U5
     select HAS_PERIPH_FLASHPAGE_PAGEWISE
     select HAS_PERIPH_HWRNG
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
     select HAS_PERIPH_WDT
     select HAS_BOOTLOADER_STM32
 

cpu/stm32/kconfigs/wb/Kconfig

@@ -14,6 +14,7 @@ config CPU_FAM_WB
     select HAS_PERIPH_FLASHPAGE_PAGEWISE
     select HAS_PERIPH_HWRNG
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
     select HAS_PERIPH_WDT
     select HAS_BOOTLOADER_STM32
 

cpu/stm32/kconfigs/wl/Kconfig

@@ -14,6 +14,7 @@ config CPU_FAM_WL
     select HAS_PERIPH_FLASHPAGE
     select HAS_PERIPH_FLASHPAGE_PAGEWISE
     select HAS_PERIPH_RTC_MEM
+    select HAS_PERIPH_VBAT
     select HAS_PERIPH_WDT
     select HAS_BOOTLOADER_STM32
 

cpu/stm32/periph/adc_f0_g0.c

@@ -22,6 +22,14 @@
 #include "cpu.h"
 #include "mutex.h"
 #include "periph/adc.h"
+#include "periph/vbat.h"
+
+/**
+ * @brief   Default VBAT undefined value
+ */
+#ifndef VBAT_ADC
+#define VBAT_ADC    ADC_UNDEF
+#endif
 
 /**
  * @brief   Allocate lock for the ADC device
@@ -62,7 +70,9 @@ int adc_init(adc_t line)
     /* lock and power on the device */
     prep();
     /* configure the pin */
-    gpio_init_analog(adc_config[line].pin);
+    if (adc_config[line].pin != GPIO_UNDEF) {
+        gpio_init_analog(adc_config[line].pin);
+    }
     /* reset configuration */
     ADC1->CFGR2 = 0;
     /* enable device */
@@ -86,7 +96,10 @@ int32_t adc_sample(adc_t line,  adc_res_t res)
 
     /* lock and power on the ADC device  */
     prep();
-
+    /* check if this is the VBAT line */
+    if (IS_USED(MODULE_PERIPH_VBAT) && line == VBAT_ADC) {
+        vbat_enable();
+    }
     /* set resolution and channel */
     ADC1->CFGR1 = res;
     ADC1->CHSELR = (1 << adc_config[line].chan);
@@ -95,7 +108,10 @@ int32_t adc_sample(adc_t line,  adc_res_t res)
     while (!(ADC1->ISR & ADC_ISR_EOC)) {}
     /* read result */
     sample = (int)ADC1->DR;
-
+    /* check if this is the VBAT line */
+    if (IS_USED(MODULE_PERIPH_VBAT) && line == VBAT_ADC) {
+        vbat_disable();
+    }
     /* unlock and power off device again */
     done();
 

cpu/stm32/periph/adc_f2.c

@@ -24,12 +24,20 @@
 #include "mutex.h"
 #include "periph/adc.h"
 #include "periph_conf.h"
+#include "periph/vbat.h"
 
 /**
  * @brief   Maximum allowed ADC clock speed
  */
 #define MAX_ADC_SPEED           (12000000U)
 
+/**
+ * @brief   Default VBAT undefined value
+ */
+#ifndef VBAT_ADC
+#define VBAT_ADC    ADC_UNDEF
+#endif
+
 /**
  * @brief   Allocate locks for all three available ADC devices
  */
@@ -73,7 +81,9 @@ int adc_init(adc_t line)
     prep(line);
 
     /* configure the pin */
-    gpio_init_analog(adc_config[line].pin);
+    if (adc_config[line].pin != GPIO_UNDEF) {
+        gpio_init_analog(adc_config[line].pin);
+    }
     /* set clock prescaler to get the maximal possible ADC clock value */
     for (clk_div = 2; clk_div < 8; clk_div += 2) {
         if ((CLOCK_CORECLOCK / clk_div) <= MAX_ADC_SPEED) {
@@ -85,17 +95,6 @@ int adc_init(adc_t line)
     /* enable the ADC module */
     dev(line)->CR2 = ADC_CR2_ADON;
 
-    /* check if this channel is an internal ADC channel, if so
-     * enable the internal temperature and Vref */
-    if (adc_config[line].chan == 16 || adc_config[line].chan == 17) {
-        /* check if the internal channels are configured to use ADC1 */
-        if (dev(line) != ADC1) {
-            return -3;
-        }
-
-        ADC->CCR |= ADC_CCR_TSVREFE;
-    }
-
     /* free the device again */
     done(line);
     return 0;
@@ -112,7 +111,15 @@ int32_t adc_sample(adc_t line, adc_res_t res)
 
     /* lock and power on the ADC device  */
     prep(line);
-
+    /* check if this is the VBAT line or another internal ADC channel */
+    if (IS_USED(MODULE_PERIPH_VBAT) && line == VBAT_ADC) {
+        vbat_enable();
+    }
+    else if (dev(line) == ADC1) {
+        if (adc_config[line].chan == 16 || adc_config[line].chan == 17) {
+            ADC->CCR |= ADC_CCR_TSVREFE;
+        }
+    }
     /* set resolution and conversion channel */
     dev(line)->CR1 = res;
     dev(line)->SQR3 = adc_config[line].chan;
@@ -121,7 +128,15 @@ int32_t adc_sample(adc_t line, adc_res_t res)
     while (!(dev(line)->SR & ADC_SR_EOC)) {}
     /* finally read sample and reset the STRT bit in the status register */
     sample = (int)dev(line)->DR;
-
+    /* check if this is the VBAT line or another internal ADC channel */
+    if (IS_USED(MODULE_PERIPH_VBAT) && line == VBAT_ADC) {
+        vbat_disable();
+    }
+    else if (dev(line) == ADC1) {
+        if (adc_config[line].chan == 16 || adc_config[line].chan == 17) {
+            ADC->CCR &= ~ADC_CCR_TSVREFE;
+        }
+    }
     /* power off and unlock device again */
     done(line);
 

cpu/stm32/periph/adc_f3.c

@@ -24,6 +24,7 @@
 #include "periph/adc.h"
 #include "periph_conf.h"
 #include "ztimer.h"
+#include "periph/vbat.h"
 
 #define SMP_MIN         (0x2) /*< Sampling time for slow channels
                                   (0x2 = 4.5 ADC clock cycles) */
@@ -33,6 +34,13 @@
 #define ADC_INSTANCE    ADC12_COMMON
 #endif
 
+/**
+ * @brief   Default VBAT undefined value
+ */
+#ifndef VBAT_ADC
+#define VBAT_ADC    ADC_UNDEF
+#endif
+
 /**
  * @brief   Allocate locks for all available ADC devices
  */
@@ -128,8 +136,9 @@ int adc_init(adc_t line)
     }
 
     /* Configure the pin */
-    gpio_init_analog(adc_config[line].pin);
+    if (adc_config[line].pin != GPIO_UNDEF) {
-
+        gpio_init_analog(adc_config[line].pin);
+    }
     /* Init ADC line only if it wasn't already initialized */
     if (!(dev(line)->CR & ADC_CR_ADEN)) {
         /* Enable ADC internal voltage regulator and wait for startup period */
@@ -192,6 +201,11 @@ int32_t adc_sample(adc_t line, adc_res_t res)
     /* Lock and power on the ADC device */
     prep(line);
 
+    /* check if this is the VBAT line */
+    if (IS_USED(MODULE_PERIPH_VBAT) && line == VBAT_ADC) {
+        vbat_enable();
+    }
+
     /* Set resolution */
     dev(line)->CFGR &= ~ADC_CFGR_RES;
     dev(line)->CFGR |= res;
@@ -206,6 +220,11 @@ int32_t adc_sample(adc_t line, adc_res_t res)
     /* Read the sample */
     sample = (int)dev(line)->DR;
 
+    /* check if this is the VBAT line */
+    if (IS_USED(MODULE_PERIPH_VBAT) && line == VBAT_ADC) {
+        vbat_disable();
+    }
+
     /* Power off and unlock device again */
     done(line);
 

cpu/stm32/periph/adc_f4_f7.c

@@ -23,12 +23,26 @@
 #include "mutex.h"
 #include "periph/adc.h"
 #include "periph_conf.h"
+#include "periph/vbat.h"
 
 /**
  * @brief   Maximum allowed ADC clock speed
  */
 #define MAX_ADC_SPEED           (12000000U)
 
+/**
+ * @brief   Maximum sampling time for each channel (480 cycles)
+ *          T_CONV[µs] = (RESOLUTION[bits] + SMP[cycles]) / CLOCK_SPEED[MHz]
+ */
+#define MAX_ADC_SMP             (7u)
+
+/**
+ * @brief   Default VBAT undefined value
+ */
+#ifndef VBAT_ADC
+#define VBAT_ADC    ADC_UNDEF
+#endif
+
 /**
  * @brief   Allocate locks for all three available ADC devices
  */
@@ -72,7 +86,9 @@ int adc_init(adc_t line)
     prep(line);
 
     /* configure the pin */
-    gpio_init_analog(adc_config[line].pin);
+    if (adc_config[line].pin != GPIO_UNDEF) {
+        gpio_init_analog(adc_config[line].pin);
+    }
     /* set sequence length to 1 conversion and enable the ADC device */
     dev(line)->SQR1 = 0;
     dev(line)->CR2 = ADC_CR2_ADON;
@@ -83,7 +99,15 @@ int adc_init(adc_t line)
         }
     }
     ADC->CCR = ((clk_div / 2) - 1) << 16;
-
+    /* set sampling time to the maximum */
+    if (adc_config[line].chan >= 10) {
+        dev(line)->SMPR1 &= ~(MAX_ADC_SMP << (3 * (adc_config[line].chan - 10)));
+        dev(line)->SMPR1 |= MAX_ADC_SMP << (3 * (adc_config[line].chan - 10));
+    }
+    else {
+        dev(line)->SMPR1 &= ~(MAX_ADC_SMP << (3 * adc_config[line].chan));
+        dev(line)->SMPR2 |= MAX_ADC_SMP << (3 * adc_config[line].chan);
+    }
     /* free the device again */
     done(line);
     return 0;
@@ -100,7 +124,10 @@ int32_t adc_sample(adc_t line, adc_res_t res)
 
     /* lock and power on the ADC device  */
     prep(line);
-
+    /* check if this channel is an internal ADC channel */
+    if (IS_USED(MODULE_PERIPH_VBAT) && line == VBAT_ADC) {
+        vbat_enable();
+    }
     /* set resolution and conversion channel */
     dev(line)->CR1 = res;
     dev(line)->SQR3 = adc_config[line].chan;
@@ -109,7 +136,10 @@ int32_t adc_sample(adc_t line, adc_res_t res)
     while (!(dev(line)->SR & ADC_SR_EOC)) {}
     /* finally read sample and reset the STRT bit in the status register */
     sample = (int)dev(line)->DR;
-
+    /* check if this channel was an internal ADC channel */
+    if (IS_USED(MODULE_PERIPH_VBAT) && line == VBAT_ADC) {
+        vbat_disable();
+    }
     /* power off and unlock device again */
     done(line);
 

cpu/stm32/periph/adc_l4.c

@@ -25,6 +25,7 @@
 #include "mutex.h"
 #include "periph/adc.h"
 #include "periph_conf.h"
+#include "periph/vbat.h"
 #include "ztimer.h"
 
 /**
@@ -55,6 +56,13 @@
 #define ADC_SMPR2_FIRST_CHAN (10)
 #endif
 
+/**
+ * @brief   Default VBAT undefined value
+ */
+#ifndef VBAT_ADC
+#define VBAT_ADC    ADC_UNDEF
+#endif
+
 /**
  * @brief   Allocate locks for all three available ADC devices
  */
@@ -122,8 +130,9 @@ int adc_init(adc_t line)
     }
 
     /* configure the pin */
-    gpio_init_analog(adc_config[line].pin);
+    if (adc_config[line].pin != GPIO_UNDEF) {
-
+        gpio_init_analog(adc_config[line].pin);
+    }
 #if defined(CPU_MODEL_STM32L476RG) || defined(CPU_MODEL_STM32L475VG)
     /* On STM32L475xx/476xx/486xx devices, before any conversion of an input channel coming
        from GPIO pads, it is necessary to configure the corresponding GPIOx_ASCR register in
@@ -192,6 +201,11 @@ int32_t adc_sample(adc_t line, adc_res_t res)
     /* lock and power on the ADC device  */
     prep(line);
 
+    /* check if this is the VBAT line */
+    if (IS_USED(MODULE_PERIPH_VBAT) && line == VBAT_ADC) {
+        vbat_enable();
+    }
+
     /* first clear resolution */
     dev(line)->CFGR &= ~(ADC_CFGR_RES);
 
@@ -208,6 +222,11 @@ int32_t adc_sample(adc_t line, adc_res_t res)
     /* read the sample */
     sample = (int)dev(line)->DR;
 
+    /* check if this is the VBAT line */
+    if (IS_USED(MODULE_PERIPH_VBAT) && line == VBAT_ADC) {
+        vbat_disable();
+    }
+
     /* free the device again */
     done(line);
 

cpu/stm32/periph/adc_wl.c

@@ -27,8 +27,16 @@
 #include "mutex.h"
 #include "periph/adc.h"
 #include "periph_conf.h"
+#include "periph/vbat.h"
 #include "ztimer.h"
 
+/**
+ * @brief   Default VBAT undefined value
+ */
+#ifndef VBAT_ADC
+#define VBAT_ADC    ADC_UNDEF
+#endif
+
 /**
  * @brief   Allocate lock for the ADC device
  *
@@ -59,7 +67,9 @@ int adc_init(adc_t line)
     prep();
 
     /* configure the pin */
-    gpio_init_analog(adc_config[line].pin);
+    if (adc_config[line].pin != GPIO_UNDEF) {
+        gpio_init_analog(adc_config[line].pin);
+    }
 
     /* init ADC line only if it wasn't already initialized */
     if (!(ADC->CR & (ADC_CR_ADEN))) {
@@ -116,6 +126,11 @@ int32_t adc_sample(adc_t line, adc_res_t res)
     /* lock and power on the ADC device  */
     prep();
 
+    /* check if this is the VBAT line */
+    if (IS_USED(MODULE_PERIPH_VBAT) && line == VBAT_ADC) {
+        vbat_enable();
+    }
+
     /* first clear resolution */
     ADC->CFGR1 &= ~ADC_CFGR1_RES;
 
@@ -132,6 +147,11 @@ int32_t adc_sample(adc_t line, adc_res_t res)
     /* read the sample */
     sample = (int)ADC->DR;
 
+    /* check if this is the VBAT line */
+    if (IS_USED(MODULE_PERIPH_VBAT) && line == VBAT_ADC) {
+        vbat_disable();
+    }
+
     /* free the device again */
     done();
 

cpu/stm32/periph/vbat.c

@@ -0,0 +1,230 @@
+/*
+ * Copyright (C) 2022 Otto-von-Guericke-Universität Magdeburg
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     cpu_stm32
+ * @ingroup     drivers_periph_vbat
+ * @{
+ *
+ * @file
+ * @brief       Implementation of STM32 backup battery monitoring
+ *
+ * @author      Fabian Hüßler <fabian.huessler@ovgu.de>
+ * @}
+ */
+
+#include "board.h"
+#include "periph_conf.h"
+#include "periph/adc.h"
+#include "periph/vbat.h"
+
+/**
+ * @name   Constants depending on CPU line
+ * @{
+ *
+ * @ref VBAT_ADC_SCALE is a scale factor to calculate the right voltage value
+ * as documented in the data sheet.
+ * @ref VBAT_ADC_MIN_MV <= VBAT[mV] is the smallest voltage level required
+ * to power the backup domain.
+ */
+/* f0 */
+#if   defined(CPU_LINE_STM32F031x6) || defined(CPU_LINE_STM32F038xx)    || \
+      defined(CPU_LINE_STM32F042x6) || defined(CPU_LINE_STM32F048xx)    || \
+      defined(CPU_LINE_STM32F051x8) || defined(CPU_LINE_STM32F058xx)    || \
+      defined(CPU_LINE_STM32F071xB) || defined(CPU_LINE_STM32F072xB)    || \
+      defined(CPU_LINE_STM32F078xx) || defined(CPU_LINE_STM32F091xC)    || \
+      defined(CPU_LINE_STM32F098xx)
+#define VBAT_ADC_SCALE        2
+#define VBAT_ADC_MIN_MV       1650
+/* f2 */
+#elif defined(CPU_LINE_STM32F205xx) || defined(CPU_LINE_STM32F207xx)    || \
+      defined(CPU_LINE_STM32F215xx) || defined(CPU_LINE_STM32F217xx)
+#define VBAT_ADC_SCALE        2
+#define VBAT_ADC_MIN_MV       1800
+/* f3 */
+#elif defined(CPU_LINE_STM32F301x8) || defined(CPU_LINE_STM32F302x8)    || \
+      defined(CPU_LINE_STM32F302xC) || defined(CPU_LINE_STM32F302xE)    || \
+      defined(CPU_LINE_STM32F303x8) || defined(CPU_LINE_STM32F303xC)    || \
+      defined(CPU_LINE_STM32F303xE) || defined(CPU_LINE_STM32F318x8)    || \
+      defined(CPU_LINE_STM32F318xx) || defined(CPU_LINE_STM32F328xx)    || \
+      defined(CPU_LINE_STM32F334x8) || defined(CPU_LINE_STM32F358xx)    || \
+      defined(CPU_LINE_STM32F373xC) || defined(CPU_LINE_STM32F378xx)    || \
+      defined(CPU_LINE_STM32F398xx)
+#define VBAT_ADC_SCALE        2
+#define VBAT_ADC_MIN_MV       1650
+/* f4 */
+#elif defined(CPU_LINE_STM32F401xC) || defined(CPU_LINE_STM32F401xE)    || \
+      defined(CPU_LINE_STM32F410Cx) || defined(CPU_LINE_STM32F410Rx)    || \
+      defined(CPU_LINE_STM32F410Tx) || defined(CPU_LINE_STM32F411xE)    || \
+      defined(CPU_LINE_STM32F412Cx) || defined(CPU_LINE_STM32F412Rx)    || \
+      defined(CPU_LINE_STM32F412Vx) || defined(CPU_LINE_STM32F412Zx)    || \
+      defined(CPU_LINE_STM32F413xx) || defined(CPU_LINE_STM32F423xx)    || \
+      defined(CPU_LINE_STM32F427xx) || defined(CPU_LINE_STM32F429xx)    || \
+      defined(CPU_LINE_STM32F437xx) || defined(CPU_LINE_STM32F439xx)    || \
+      defined(CPU_LINE_STM32F446xx) || defined(CPU_LINE_STM32F469xx)    || \
+      defined(CPU_LINE_STM32F479xx)
+#define VBAT_ADC_SCALE        4
+#define VBAT_ADC_MIN_MV       1650
+#elif defined(CPU_LINE_STM32F405xx) || defined(CPU_LINE_STM32F407xx)    || \
+      defined(CPU_LINE_STM32F415xx) || defined(CPU_LINE_STM32F417xx)
+#define VBAT_ADC_SCALE        2
+#define VBAT_ADC_MIN_MV       1650
+/* f7 */
+#elif defined(CPU_LINE_STM32F722xx) || defined(CPU_LINE_STM32F723xx)    || \
+      defined(CPU_LINE_STM32F730xx) || defined(CPU_LINE_STM32F732xx)    || \
+      defined(CPU_LINE_STM32F733xx) || defined(CPU_LINE_STM32F745xx)    || \
+      defined(CPU_LINE_STM32F746xx) || defined(CPU_LINE_STM32F750xx)    || \
+      defined(CPU_LINE_STM32F756xx) || defined(CPU_LINE_STM32F765xx)    || \
+      defined(CPU_LINE_STM32F767xx) || defined(CPU_LINE_STM32F769xx)    || \
+      defined(CPU_LINE_STM32F777xx) || defined(CPU_LINE_STM32F779xx)
+#define VBAT_ADC_SCALE        4
+#define VBAT_ADC_MIN_MV       1650
+/* g0 */
+#elif defined(CPU_LINE_STM32G030xx) || defined(CPU_LINE_STM32G031xx)    || \
+      defined(CPU_LINE_STM32G041xx) || defined(CPU_LINE_STM32G050xx)    || \
+      defined(CPU_LINE_STM32G051xx) || defined(CPU_LINE_STM32G061xx)    || \
+      defined(CPU_LINE_STM32G070xx) || defined(CPU_LINE_STM32G071xx)    || \
+      defined(CPU_LINE_STM32G081xx) || defined(CPU_LINE_STM32G0B0xx)    || \
+      defined(CPU_LINE_STM32G0B1xx) || defined(CPU_LINE_STM32G0C1xx)
+#define VBAT_ADC_SCALE        3
+#define VBAT_ADC_MIN_MV       1550
+/* g4 */
+#elif defined(CPU_LINE_STM32G431xx) || defined(CPU_LINE_STM32G441xx)    || \
+      defined(CPU_LINE_STM32G471xx) || defined(CPU_LINE_STM32G473xx)    || \
+      defined(CPU_LINE_STM32G474xx) || defined(CPU_LINE_STM32G483xx)    || \
+      defined(CPU_LINE_STM32G484xx) || defined(CPU_LINE_STM32G491xx)    || \
+      defined(CPU_LINE_STM32G4A1xx) || defined(CPU_LINE_STM32G441xx)    || \
+      defined(CPU_LINE_STM32GBK1CB)
+#define VBAT_ADC_SCALE        3
+#define VBAT_ADC_MIN_MV       1550
+/* l4 */
+#elif defined(CPU_LINE_STM32L412xx) || defined(CPU_LINE_STM32L422xx)    || \
+      defined(CPU_LINE_STM32L431xx) || defined(CPU_LINE_STM32L432xx)    || \
+      defined(CPU_LINE_STM32L433xx) || defined(CPU_LINE_STM32L442xx)    || \
+      defined(CPU_LINE_STM32L443xx) || defined(CPU_LINE_STM32L451xx)    || \
+      defined(CPU_LINE_STM32L452xx) || defined(CPU_LINE_STM32L462xx)    || \
+      defined(CPU_LINE_STM32L471xx) || defined(CPU_LINE_STM32L475xx)    || \
+      defined(CPU_LINE_STM32L476xx) || defined(CPU_LINE_STM32L485xx)    || \
+      defined(CPU_LINE_STM32L486xx) || defined(CPU_LINE_STM32L496xx)    || \
+      defined(CPU_LINE_STM32L4A6xx) || defined(CPU_LINE_STM32L4P5xx)    || \
+      defined(CPU_LINE_STM32L4Q5xx) || defined(CPU_LINE_STM32L4R5xx)    || \
+      defined(CPU_LINE_STM32L4R7xx) || defined(CPU_LINE_STM32L4R9xx)    || \
+      defined(CPU_LINE_STM32L4S5xx) || defined(CPU_LINE_STM32L4S7xx)    || \
+      defined(CPU_LINE_STM32L4S9xx)
+#define VBAT_ADC_SCALE        3
+#define VBAT_ADC_MIN_MV       1550
+/* l5 */
+#elif defined(CPU_LINE_STM32L552xx) || defined(CPU_LINE_STM32L562xx)
+#define VBAT_ADC_SCALE        3
+#define VBAT_ADC_MIN_MV       1550
+/* u5 */
+#elif defined(CPU_LINE_STM32U575xx) || defined(CPU_LINE_STM32U585xx)
+#define VBAT_ADC_SCALE        4
+#define VBAT_ADC_MIN_MV       1650
+/* wb */
+#elif defined(CPU_LINE_STM32WB10xx) || defined(CPU_LINE_STM32WB15xx)    || \
+      defined(CPU_LINE_STM32WB30xx) || defined(CPU_LINE_STM32WB35xx)    || \
+      defined(CPU_LINE_STM32WB50xx) || defined(CPU_LINE_STM32WB55xx)    || \
+      defined(CPU_LINE_STM32WB5Mxx)
+#define VBAT_ADC_SCALE        3
+#define VBAT_ADC_MIN_MV       1550
+/* wl */
+#elif defined(CPU_LINE_STM32WL54xx) || defined(CPU_LINE_STM32WL55xx)    || \
+      defined(CPU_LINE_STM32WLE4xx) || defined(CPU_LINE_STM32WLE5xx)
+#define VBAT_ADC_SCALE        3
+#define VBAT_ADC_MIN_MV       1550
+#else
+#error "VBAT: CPU line is not supported so far."
+#endif
+/** @} */
+
+/**
+ * @name    VBAT enable register
+ * @{
+ */
+#if defined(CPU_LINE_STM32F373xC) || defined(CPU_LINE_STM32F378xx)
+#define ADC_CCR_REG (SYSCFG->CFGR1) /* ADCx_COMMON is also defined */
+#elif defined(ADC_COMMON)
+#define ADC_CCR_REG (ADC_COMMON->CCR)
+#elif defined(ADC1_COMMON)
+#define ADC_CCR_REG (ADC1_COMMON->CCR)
+#elif defined(ADC12_COMMON)
+#define ADC_CCR_REG (ADC12_COMMON->CCR)
+#elif defined(ADC123_COMMON)
+#define ADC_CCR_REG (ADC123_COMMON->CCR)
+#elif defined(ADC12_COMMON_NS)
+#define ADC_CCR_REG (ADC12_COMMON_NS->CCR)
+#elif defined(ADC)
+#define ADC_CCR_REG (ADC->CCR)
+#else
+#error "VBAT: CPU line is not supported so far."
+#endif
+/** @} */
+
+/**
+ * @name    VBAT enable flag
+ * @{
+ */
+#if defined(ADC_CCR_VBATEN)
+#define VBAT_ENABLE ADC_CCR_VBATEN;
+#elif defined(ADC_CCR_VBATE)
+#define VBAT_ENABLE ADC_CCR_VBATE;
+#elif defined(ADC_CCR_VBATSEL)
+#define VBAT_ENABLE ADC_CCR_VBATSEL;
+#elif defined(SYSCFG_CFGR1_VBAT)
+#define VBAT_ENABLE SYSCFG_CFGR1_VBAT;
+#else
+#error "VBAT: CPU line is not supported so far."
+#endif
+/** @} */
+
+#ifndef CONFIG_VBAT_ADC_VREF_MV
+#define CONFIG_VBAT_ADC_VREF_MV 3300            /**< ADC reference voltage */
+#endif
+
+/**
+ * @brief   Override this function if you know how to retrieve the accurate
+ *          ADC supply voltage in mV for your board. The default behaviour is
+ *          to return @ref CONFIG_VBAT_ADC_VREF_MV.
+ *          Once there is a driver to sample VREFINT, this function is likely
+ *          to be changed.
+ */
+int32_t __attribute__((weak)) vref_mv(void) {
+    return CONFIG_VBAT_ADC_VREF_MV;
+}
+
+#ifndef VBAT_ADC
+#error "VBAT: Add internal VBAT ADC line to adc_config[] and #define VBAT_ADC."
+#endif
+
+int vbat_init(void)
+{
+    return adc_init(VBAT_ADC);
+}
+
+void vbat_enable(void)
+{
+    ADC_CCR_REG |= VBAT_ENABLE;
+}
+
+void vbat_disable(void)
+{
+    ADC_CCR_REG &= ~VBAT_ENABLE;
+}
+
+int32_t vbat_sample_mv(void)
+{
+    int32_t mv = adc_sample(VBAT_ADC, VBAT_ADC_RES);
+    mv = (mv * VBAT_ADC_SCALE * vref_mv()) / VBAT_ADC_MAX;
+    return mv;
+}
+
+bool vbat_is_empty(void)
+{
+    return VBAT_ADC_MIN_MV > vbat_sample_mv();
+}

drivers/include/periph/vbat.h

@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2022 Otto-von-Guericke-Universität Magdeburg
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup    drivers_periph_vbat backup battery monitoring
+ * @ingroup     drivers_periph
+ * @brief       Driver to monitor the internal backup battery status
+ *
+ * The backup battery must be connected with the VBAT pin and GND.
+ * On most development boards you will have to remove a solder bridge
+ * that connects VDD with VBAT. The battery is used to retain the backup domain
+ * register and RTC register content while power (VDD) is off.
+ *
+ * The actual driver is implemented as a CPU feature.
+ * A board that supports
+ * backup battery monitoring via ADC, must `#define VBAT_ADC ADC_LINE(x)`,
+ * where `x` is the index of the internal VBAT ADC line in `adc_config[]`
+ * in periph_conf.h.
+ *
+ * @{
+ *
+ * @file
+ * @brief       Interface of backup battery (VBAT) monitoring
+ *
+ * @author      Fabian Hüßler <fabian.huessler@ovgu.de>
+ */
+
+#ifndef PERIPH_VBAT_H
+#define PERIPH_VBAT_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief       Initialize backup battery monitoring
+ *
+ * @retval      != 0: Failure
+ * @retval      0: Success
+ */
+int vbat_init(void);
+
+/**
+ * @brief       Sample backup battery
+ *
+ * @return      Backup battery load in mV
+ */
+int32_t vbat_sample_mv(void);
+
+/**
+ * @brief       Sample the backup battery and compare the result with
+ *              the minimum value required to power the backup domain
+ *
+ * @retval      true: empty
+ * @retval      false: not empty
+ */
+bool vbat_is_empty(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* PERIPH_VBAT_H */
+/** @} */

drivers/periph_common/Kconfig

@@ -170,4 +170,5 @@ config HAVE_SHARED_PERIPH_RTT_PERIPH_RTC
         only one can be selected.
 
 rsource "Kconfig.timer"
+rsource "Kconfig.vbat"
 rsource "Kconfig.wdt"

drivers/periph_common/Kconfig.vbat

@@ -0,0 +1,39 @@
+# Copyright (c) 2022 Otto-von-Guericke-Universität Magdeburg
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+#
+
+menuconfig MODULE_PERIPH_VBAT
+    bool "Backup Battery monitoring driver"
+    depends on HAS_PERIPH_VBAT
+    depends on HAS_PERIPH_ADC
+    depends on TEST_KCONFIG
+    select MODULE_PERIPH_ADC
+
+if MODULE_PERIPH_VBAT
+
+config MODULE_PERIPH_INIT_VBAT
+    bool "Auto initialize VBAT ADC line"
+    default y if MODULE_PERIPH_INIT
+
+config VBAT_ADC_VREF_MV
+    int "ADC reference voltage in mV"
+    default 3300
+
+endif # MODULE_PERIPH_VBAT
+
+menuconfig KCONFIG_USEMODULE_PERIPH_VBAT
+    bool "Configure backup battery monitoring peripheral driver"
+    depends on USEMODULE_PERIPH_VBAT
+    help
+        Configure backup battery monitoring peripheral driver using Kconfig.
+
+config VBAT_ADC_VREF_MV
+    int "ADC reference voltage in mV"
+    default 3300
+    depends on KCONFIG_USEMODULE_PERIPH_VBAT
+    help
+        This is the reference voltage (VREF) of the ADC.
+        Often VREF is connected with VDDA, which is equal to VDD.

drivers/periph_common/init.c

@@ -50,6 +50,9 @@
 #ifdef MODULE_PERIPH_INIT_PTP
 #include "periph/ptp.h"
 #endif
+#ifdef MODULE_PERIPH_INIT_VBAT
+#include "periph/vbat.h"
+#endif
 #endif /* MODULE_PERIPH_INIT */
 
 void periph_init(void)
@@ -105,5 +108,9 @@ void periph_init(void)
     ptp_init();
 #endif
 
+#if defined(MODULE_PERIPH_INIT_VBAT)
+    vbat_init();
+#endif
+
 #endif /* MODULE_PERIPH_INIT */
 }

kconfigs/Kconfig.features

@@ -369,6 +369,11 @@ config HAS_PERIPH_USBDEV
     help
         Indicates that an USBDEV peripheral is present.
 
+config HAS_PERIPH_VBAT
+    bool
+    help
+        Indicates that backup battery monitoring is supported
+
 config HAS_PERIPH_WDT
     bool
     help

tests/periph_vbat/Makefile

@@ -0,0 +1,6 @@
+include ../Makefile.tests_common
+
+FEATURES_REQUIRED += periph_vbat
+USEMODULE += ztimer ztimer_msec
+
+include $(RIOTBASE)/Makefile.include

tests/periph_vbat/README.md

@@ -0,0 +1,5 @@
+Backup Battery Monitoring Application
+=====================================
+
+This test regularly samples the backup battery voltage and prints the result
+to the serial console.

tests/periph_vbat/app.config.test

@@ -0,0 +1,5 @@
+# this file enables modules defined in Kconfig. Do not use this file for
+# application configuration. This is only needed during migration.
+CONFIG_MODULE_ZTIMER=y
+CONFIG_MODULE_ZTIMER_MSEC=y
+CONFIG_MODULE_PERIPH_VBAT=y

tests/periph_vbat/main.c

@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2022 Otto-von-Guericke-Universität Magdeburg
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     tests
+ * @{
+ *
+ * @file
+ * @brief       Test application for backup battery monitoring
+ *
+ * @author      Fabian Hüßler <fabian.huessler@ovgu.de>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+#include <inttypes.h>
+
+#include "board.h"
+#include "ztimer.h"
+#include "periph/vbat.h"
+
+int main(void)
+{
+    puts("\nRIOT backup battery monitoring test\n");
+    puts("This test will sample the backup battery once a second\n\n");
+
+    int32_t bat_mv;
+    while (1) {
+        if ((bat_mv = vbat_sample_mv()) < 0) {
+            return 1;
+        }
+        printf("VBAT: %"PRIi32"[mV]\n", bat_mv);
+        ztimer_sleep(ZTIMER_MSEC, 1000);
+    }
+    return 0;
+}