stm32/adc: Disable VBAT in read channel helper function.

Prior to this patch, if VBAT was read via ADC.read() or
ADCAll.read_channel(), then it would remain enabled and subsequent reads
of TEMPSENSOR or VREFINT would not work.  This patch makes sure that VBAT
is disabled for all cases that it could be read.

1 files changed, 14 insertions, 10 deletions

diff --git a/ports/stm32/adc.c b/ports/stm32/adc.c
index d0689cd8c..4755a8ede 100644
--- a/ports/stm32/adc.c
+++ b/ports/stm32/adc.c
@@ -315,7 +315,20 @@ STATIC uint32_t adc_read_channel(ADC_HandleTypeDef *adcHandle) {
 
 STATIC uint32_t adc_config_and_read_channel(ADC_HandleTypeDef *adcHandle, uint32_t channel) {
     adc_config_channel(adcHandle, channel);
-    return adc_read_channel(adcHandle);
+    uint32_t raw_value = adc_read_channel(adcHandle);
+
+    #if defined(STM32F4) || defined(STM32F7)
+    // ST docs say that (at least on STM32F42x and STM32F43x), VBATE must
+    // be disabled when TSVREFE is enabled for TEMPSENSOR and VREFINT
+    // conversions to work.  VBATE is enabled by the above call to read
+    // the channel, and here we disable VBATE so a subsequent call for
+    // TEMPSENSOR or VREFINT works correctly.
+    if (channel == ADC_CHANNEL_VBAT) {
+        ADC->CCR &= ~ADC_CCR_VBATE;
+    }
+    #endif
+
+    return raw_value;
 }
 
 /******************************************************************************/
@@ -692,15 +705,6 @@ float adc_read_core_vbat(ADC_HandleTypeDef *adcHandle) {
     //       be 12-bits.
     raw_value <<= (12 - adc_get_resolution(adcHandle));
 
-    #if defined(STM32F4) || defined(STM32F7)
-    // ST docs say that (at least on STM32F42x and STM32F43x), VBATE must
-    // be disabled when TSVREFE is enabled for TEMPSENSOR and VREFINT
-    // conversions to work.  VBATE is enabled by the above call to read
-    // the channel, and here we disable VBATE so a subsequent call for
-    // TEMPSENSOR or VREFINT works correctly.
-    ADC->CCR &= ~ADC_CCR_VBATE;
-    #endif
-
     return raw_value * VBAT_DIV * ADC_SCALE * adc_refcor;
 }