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Merge #19629

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19629: cpu/stm32/periph/adc: fix setting ADC clock r=benpicco a=Enoch247

### Contribution description

The current implementation uses the core clock frequency to calculate the needed prescalar to achieve a given ADC clock frequency. This is incorrect. This patch fixes the calculation to use the correct source clock (PCKLK2 ie APB2). It also changes the defined max clock rate to use the frequency macro to improve readability.

I based on code similarity. I believe the gd32v CPU may need this same fix, but I am not familiar with that MCU.

### Testing procedure

I tested this on a nucleo-f767zi. The the MCU's reference manual is in agreement with what I have implemented here. I spot checked references manuals for a random [STM32F1](https://www.st.com/resource/en/reference_manual/cd00171190-stm32f101xx-stm32f102xx-stm32f103xx-stm32f105xx-and-stm32f107xx-advanced-arm-based-32-bit-mcus-stmicroelectronics.pdf) and [STM32F2](https://www.st.com/resource/en/reference_manual/rm0033-stm32f205xx-stm32f207xx-stm32f215xx-and-stm32f217xx-advanced-armbased-32bit-mcus-stmicroelectronics.pdf), and they are clocked similar to the F7 I have.

### Issues/PRs references

None known.


Co-authored-by: Joshua DeWeese <jdeweese@primecontrols.com>
This commit is contained in:
bors[bot] 2023-05-28 05:23:29 +00:00 committed by GitHub
commit f08ab0814c
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3 changed files with 6 additions and 6 deletions
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4
cpu/stm32/periph/adc_f1.c
View File

@ -28,7 +28,7 @@
/**
* @brief Maximum allowed ADC clock speed
*/
#define MAX_ADC_SPEED (14000000U)
#define MAX_ADC_SPEED MHZ(14)
/**
* @brief Allocate locks for all three available ADC devices
@ -93,7 +93,7 @@ int adc_init(adc_t line)
}
/* 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) {
if ((periph_apb_clk(APB2) / clk_div) <= MAX_ADC_SPEED) {
break;
}
}

4
cpu/stm32/periph/adc_f2.c
View File

@ -29,7 +29,7 @@
/**
* @brief Maximum allowed ADC clock speed
*/
#define MAX_ADC_SPEED (12000000U)
#define MAX_ADC_SPEED MHZ(12)
/**
* @brief Default VBAT undefined value
@ -86,7 +86,7 @@ int adc_init(adc_t line)
}
/* 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) {
if ((periph_apb_clk(APB2) / clk_div) <= MAX_ADC_SPEED) {
break;
}
}

4
cpu/stm32/periph/adc_f4_f7.c
View File

@ -28,7 +28,7 @@
/**
* @brief Maximum allowed ADC clock speed
*/
#define MAX_ADC_SPEED (12000000U)
#define MAX_ADC_SPEED MHZ(12)
/**
* @brief Maximum sampling time for each channel (480 cycles)
@ -94,7 +94,7 @@ int adc_init(adc_t line)
dev(line)->CR2 = ADC_CR2_ADON;
/* 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) {
if ((periph_apb_clk(APB2) / clk_div) <= MAX_ADC_SPEED) {
break;
}
}