STM32F1 ADC: remove adc_inited flag

targets/TARGET_STM/TARGET_STM32F1/analogin_api.c

@@ -36,10 +36,9 @@
 #include "mbed_error.h"
 #include "PeripheralPins.h"
 
-int adc_inited = 0;
-
 void analogin_init(analogin_t *obj, PinName pin)
 {
+    static int adc_calibrated = 0;
     RCC_PeriphCLKInitTypeDef  PeriphClkInit;
     uint32_t function = (uint32_t)NC;
 
@@ -68,24 +67,10 @@ void analogin_init(analogin_t *obj, PinName pin)
     // Save pin number for the read function
     obj->pin = pin;
 
-    // The ADC initialization is done once
-    if (adc_inited == 0) {
-        adc_inited = 1;
-
     // Enable ADC clock
     __HAL_RCC_ADC1_CLK_ENABLE();
 
-        // Configure ADC clock prescaler
+    // Configure ADC object structures
-        // Caution: On STM32F1, ADC clock frequency max is 14 MHz (refer to device datasheet).
-        // Therefore, ADC clock prescaler must be configured in function
-        // of ADC clock source frequency to remain below this maximum frequency.
-        // with 8 MHz external xtal: PCLK2 = 72 MHz --> ADC clock = 72/6 = 12 MHz
-        // with internal clock     : PCLK2 = 64 MHz --> ADC clock = 64/6 = 10.67 MHz
-        PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_ADC;
-        PeriphClkInit.AdcClockSelection = RCC_ADCPCLK2_DIV6;
-        HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit);
-
-        // Configure ADC
     obj->handle.State = HAL_ADC_STATE_RESET;
     obj->handle.Init.DataAlign             = ADC_DATAALIGN_RIGHT;
     obj->handle.Init.ScanConvMode          = DISABLE;
@@ -96,17 +81,29 @@ void analogin_init(analogin_t *obj, PinName pin)
     obj->handle.Init.ExternalTrigConv      = ADC_SOFTWARE_START;
 
     if (HAL_ADC_Init(&obj->handle) != HAL_OK) {
-            error("Cannot initialize ADC\n");
+        error("Cannot initialize ADC");
     }
 
-        // Calibrate ADC
+    // This section is done only once
+    if (adc_calibrated == 0) {
+        adc_calibrated = 1;
+        // Configure ADC clock prescaler
+        // Caution: On STM32F1, ADC clock frequency max is 14 MHz (refer to device datasheet).
+        // Therefore, ADC clock prescaler must be configured in function
+        // of ADC clock source frequency to remain below this maximum frequency.
+        // with 8 MHz external xtal: PCLK2 = 72 MHz --> ADC clock = 72/6 = 12 MHz
+        // with internal clock     : PCLK2 = 64 MHz --> ADC clock = 64/6 = 10.67 MHz
+        PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_ADC;
+        PeriphClkInit.AdcClockSelection = RCC_ADCPCLK2_DIV6;
+        HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit);
+        // Calibration
         HAL_ADCEx_Calibration_Start(&obj->handle);
     }
 }
 
 static inline uint16_t adc_read(analogin_t *obj)
 {
-    ADC_ChannelConfTypeDef sConfig;
+    ADC_ChannelConfTypeDef sConfig = {0};
 
     // Configure ADC channel
     sConfig.Rank         = 1;
@@ -177,7 +174,7 @@ static inline uint16_t adc_read(analogin_t *obj)
 
     // Wait end of conversion and get value
     if (HAL_ADC_PollForConversion(&obj->handle, 10) == HAL_OK) {
-        return (HAL_ADC_GetValue(&obj->handle));
+        return (uint16_t)HAL_ADC_GetValue(&obj->handle);
     } else {
         return 0;
     }