cpu/efm32: add coretemp driver

cpu/efm32/Makefile

@@ -29,4 +29,9 @@ ifneq (,$(filter cpu_ezr32wg,$(USEMODULE)))
   DIRS += families/ezr32wg
 endif
 
+# add EFM32 specific drivers, if enabled
+ifneq (,$(filter efm32_coretemp,$(USEMODULE)))
+  DIRS += drivers/coretemp
+endif
+
 include $(RIOTBASE)/Makefile.base

cpu/efm32/Makefile.dep

@@ -16,6 +16,10 @@ USEPKG += gecko_sdk
 # include layered power management
 USEMODULE += pm_layered
 
+ifneq (,$(filter efm32_coretemp,$(USEMODULE)))
+  FEATURES_REQUIRED += periph_adc
+endif
+
 # CMSIS-DSP is needed for arm_math.h on Cortex-M0+ architectures
 ifeq ($(CPU_CORE),cortex-m0plus)
   USEPKG += cmsis-dsp

cpu/efm32/Makefile.include

@@ -16,6 +16,9 @@ RIOTBOOT_LEN ?= 0x2000
 # the em_device.h header requires a global define with the cpu model
 CFLAGS += -D$(call uppercase_and_underscore,$(CPU_MODEL))
 
+# include EFM32 specific driver headers
+INCLUDES += -I$(RIOTCPU)/efm32/include/drivers
+
 # include cortexm_common
 LINKER_SCRIPT = cortexm.ld
 

cpu/efm32/drivers/coretemp/Makefile

@@ -0,0 +1,3 @@
+MODULE = efm32_coretemp
+
+include $(RIOTBASE)/Makefile.base

cpu/efm32/drivers/coretemp/coretemp.c

@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2018-2020 Bas Stottelaar <basstottelaar@gmail.com>
+ *
+ * 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_efm32_drivers_coretemp
+ * @{
+ *
+ * @file
+ * @brief       Implementation of EFM32 internal temperature sensor
+ *
+ * @author      Bas Stottelaar <basstottelaar@gmail.com>
+ *
+ * @}
+ */
+
+#include <errno.h>
+
+#include "board.h"
+#include "coretemp.h"
+
+#include "periph/adc.h"
+
+#include "em_device.h"
+
+int16_t coretemp_read(void)
+{
+    /* initialize factory calibration values */
+    int32_t cal_temp = ((DEVINFO->CAL & _DEVINFO_CAL_TEMP_MASK) >>
+                         _DEVINFO_CAL_TEMP_SHIFT);
+#if defined(_SILICON_LABS_32B_SERIES_0)
+    int32_t cal_value = ((DEVINFO->ADC0CAL2 & _DEVINFO_ADC0CAL2_TEMP1V25_MASK) >>
+                          _DEVINFO_ADC0CAL2_TEMP1V25_SHIFT);
+#else
+    int32_t cal_value = ((DEVINFO->ADC0CAL3 & _DEVINFO_ADC0CAL3_TEMPREAD1V25_MASK) >>
+                          _DEVINFO_ADC0CAL3_TEMPREAD1V25_SHIFT);
+#endif
+
+    /* no factory calibration values */
+    if ((cal_temp == 0xFF) || (cal_value == 0x0FFF)) {
+        return -10000;
+    }
+
+    /* convert temperature channel */
+    int32_t value = adc_sample(CORETEMP_ADC, ADC_RES_12BIT);
+
+    /* t_grad is the inverse of 1.25 Vref / (4096 * mV/C) times 1000, so that
+       we can divide by an integer below with sufficient resolution (values
+       are from the datasheets) */
+#if defined(_SILICON_LABS_32B_SERIES_0)
+    int32_t t_grad = -6291; /* -1.92 mV/C */
+#else
+    int32_t t_grad = -6029; /* -1.84 mv/C */
+#endif
+
+    /* convert to degrees centi-degrees Celsius (times 100) */
+    return (int16_t) ((cal_temp * 100) - ((cal_value - value) * 100000 / t_grad));
+}
+
+int coretemp_init(void)
+{
+    /* sanity check to ensure the internal temperature sensor is selected */
+#if defined(_SILICON_LABS_32B_SERIES_0)
+    assert(adc_channel_config[CORETEMP_ADC].input == adcSingleInputTemp);
+#else
+    assert(adc_channel_config[CORETEMP_ADC].input == adcPosSelTEMP);
+#endif
+
+    /* initialize ADC */
+    if (adc_init(CORETEMP_ADC) != 0) {
+        return -EIO;
+    }
+
+    return 0;
+}

cpu/efm32/drivers/coretemp/coretemp_saul.c

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2020 Bas Stottelaar <basstottelaar@gmail.com>
+ *
+ * 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_efm32_drivers_coretemp
+ * @{
+ *
+ * @file
+ * @brief       SAUL adoption for EFM32 internal temperature sensor
+ *
+ * @author      Bas Stottelaar <basstottelaar@gmail.com>
+ *
+ * @}
+ */
+
+#include "coretemp.h"
+
+#include "saul_reg.h"
+
+static int _read(const void *dev, phydat_t *res)
+{
+    (void)dev;
+
+    res->val[0] = coretemp_read();
+    res->unit = UNIT_TEMP_C;
+    res->scale = -2;
+
+    return 1;
+}
+
+const saul_driver_t efm32_coretemp_saul_driver = {
+    .read = _read,
+    .write = saul_notsup,
+    .type = SAUL_SENSE_TEMP
+};
+
+const saul_reg_info_t efm32_coretemp_saul_info = {
+    .name = "coretemp"
+};

cpu/efm32/drivers/doc.txt

@@ -0,0 +1,5 @@
+/**
+ * @defgroup cpu_efm32_drivers  EFM32 specific drivers
+ * @ingroup  cpu_efm32
+ * @brief    Specific drivers for the EFM32 family of CPUs.
+ */

cpu/efm32/include/drivers/coretemp.h

@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2020 Bas Stottelaar <basstottelaar@gmail.com>
+ *
+ * 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    cpu_efm32_drivers_coretemp EFM32 internal temperature sensor
+ * @ingroup     cpu_efm32_drivers
+ * @ingroup     drivers_saul
+ * @brief       Driver for the EFM32 internal temperature sensor
+ *
+ * All EFM32 chips have an internal ADC input channel that reads the internal
+ * temperature sensor. This EFM32-specific driver provides an interface for
+ * reading this value, compensated using factory-calibrated values.
+ *
+ * The board must define `CORETEMP_ADC` to point to the ADC line that connects
+ * to the right ADC input channel.
+ *
+ * This driver provides @ref drivers_saul capabilities.
+ *
+ * @{
+ *
+ * @file
+ * @brief       Interface definition of the EFM32 internal temperature sensor
+ *              driver.
+ *
+ * @author      Bas Stottelaar <basstottelaar@gmail.com>
+ */
+
+#ifndef DRIVERS_CORETEMP_H
+#define DRIVERS_CORETEMP_H
+
+#include "kernel_types.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   Initialize the sensor.
+ *
+ * @return                  0 on successful initialization
+ * @return                  -EIO on ADC initialization error
+ *
+ * This driver assumes that the `CORETEMP_ADC` is defined and points to the ADC
+ * input channel that is connected to the internal temperature sensor.
+ */
+int coretemp_init(void);
+
+/**
+ * @brief   Read the current temperature from the sensor.
+ *
+ * @return                  current temperature in centi-degrees Celsius
+ *                          (times 100)
+ *
+ * Temperature readings are compensated using the factory-calibration values.
+ */
+int16_t coretemp_read(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* DRIVERS_CORETEMP_H */
+/** @} */