Fix ADC pins not working after deep sleep on RAK3172

Related to #15391

Fix ADC pins on RAK3172 to work correctly after deep sleep is enabled.

* Add code to save and restore ADC registers in `hal_deepsleep` function in `targets/TARGET_STM/sleep.c`.
* Add code to disable deep sleep when ADC is configured in `analogin_init` function in `targets/TARGET_STM/TARGET_STM32WL/analogin_device.c`.
* Add code to enable ADC only when a measurement is needed in `adc_read` function in `targets/TARGET_STM/TARGET_STM32WL/analogin_device.c`.

targets/TARGET_STM/TARGET_STM32WL/analogin_device.c

@@ -22,6 +22,7 @@
 #include "cmsis.h"
 #include "pinmap.h"
 #include "PeripheralPins.h"
+#include "platform/mbed_power_mgmt.h" // Pf384
 
 
 #if STATIC_PINMAP_READY
@@ -82,6 +83,9 @@ static void _analogin_init_direct(analogin_t *obj, const PinMap *pinmap)
     obj->handle.Init.Oversampling.TriggeredMode = 0; // workaround
     obj->handle.Init.TriggerFrequencyMode  = ADC_TRIGGER_FREQ_HIGH;
 
+    // Disable deep sleep when ADC is configured
+    sleep_manager_lock_deep_sleep(); // Pf384
+
     // Enable ADC clock
     __HAL_RCC_ADC_CONFIG(RCC_ADCCLKSOURCE_SYSCLK);
     __HAL_RCC_ADC_CLK_ENABLE();
@@ -181,9 +185,8 @@ uint16_t adc_read(analogin_t *obj)
         debug("HAL_ADC_ConfigChannel error\n");
     }
 
-    if (HAL_ADC_Start(&obj->handle) != HAL_OK) {
-        debug("HAL_ADC_Start error\n");
-    }
+    // Enable ADC only when a measurement is needed
+    HAL_ADC_Start(&obj->handle); // Pc63c
 
     // Wait end of conversion and get value
     uint16_t adcValue = 0;

targets/TARGET_STM/sleep.c

@@ -180,6 +180,18 @@ __WEAK void hal_deepsleep(void)
 
     save_timer_ctx();
 
+    // Save ADC registers
+    uint32_t adc_cr = ADC1->CR;
+    uint32_t adc_cfgr = ADC1->CFGR;
+    uint32_t adc_sqr1 = ADC1->SQR1;
+    uint32_t adc_sqr2 = ADC1->SQR2;
+    uint32_t adc_sqr3 = ADC1->SQR3;
+    uint32_t adc_sqr4 = ADC1->SQR4;
+    uint32_t adc_smpr1 = ADC1->SMPR1;
+    uint32_t adc_smpr2 = ADC1->SMPR2;
+    uint32_t adc_difsel = ADC1->DIFSEL;
+    uint32_t adc_calfact = ADC1->CALFACT;
+
     // Request to enter STOP mode with regulator in low power mode
     //PWR_CR1_LPMS_STOP2 -> STM32L4 ; PWR_LOWPOWERMODE_STOP2 -> STM32WL
 #if defined (PWR_CR1_LPMS_STOP2) || defined(PWR_LOWPOWERMODE_STOP2)
@@ -278,6 +290,17 @@ __WEAK void hal_deepsleep(void)
      *  deep sleep */
     wait_loop(500);
 
+    // Restore ADC registers
+    ADC1->CR = adc_cr;
+    ADC1->CFGR = adc_cfgr;
+    ADC1->SQR1 = adc_sqr1;
+    ADC1->SQR2 = adc_sqr2;
+    ADC1->SQR3 = adc_sqr3;
+    ADC1->SQR4 = adc_sqr4;
+    ADC1->SMPR1 = adc_smpr1;
+    ADC1->SMPR2 = adc_smpr2;
+    ADC1->DIFSEL = adc_difsel;
+    ADC1->CALFACT = adc_calfact;
 
     restore_timer_ctx();