driver: adc_esp32: protect the adc reading against core migration.

On dual core esp32 the either the interrupts and the FoC task may migrate
to a different core, making the ADC registers subject to corruption if
the other core tries to manage the ADC while current core owns it, so
add a spinlock around the ADC to avoid that. On single core devices
this is call is a NOOP.

Signed-off-by: Felipe Neves <[email protected]>

Author: uLipe

src/current_sense/hardware_specific/esp32/esp32_adc_driver.cpp

@@ -6,6 +6,7 @@
 #define SIMPLEFOC_ADC_ATTEN ADC_11db
 #define SIMPLEFOC_ADC_RES 12
 
+static portMUX_TYPE spinlock =  portMUX_INITIALIZER_UNLOCKED;
 
 #if CONFIG_IDF_TARGET_ESP32 // if esp32 variant
 
@@ -38,6 +39,7 @@ void IRAM_ATTR __configFastADCs(){
     SET_PERI_REG_BITS(SENS_SAR_MEAS_WAIT1_REG, SENS_SAR_AMP_WAIT2, 0x1, SENS_SAR_AMP_WAIT2_S);
     SET_PERI_REG_BITS(SENS_SAR_MEAS_WAIT2_REG, SENS_SAR_AMP_WAIT3, 0x1, SENS_SAR_AMP_WAIT3_S);
     while (GET_PERI_REG_BITS2(SENS_SAR_SLAVE_ADDR1_REG, 0x7, SENS_MEAS_STATUS_S) != 0); //wait det_fsm==
+
 }
 
 
@@ -56,6 +58,10 @@ uint16_t IRAM_ATTR adcRead(uint8_t pin)
 
     // variable to hold the ADC value
     uint16_t value = 0;
+
+    //Protects against core migration, on single core chips this is noop.
+    portENTER_CRITICAL(&spinlock);
+
     // do the ADC conversion
     switch(adc_num){
         case 1:
@@ -82,6 +88,8 @@ uint16_t IRAM_ATTR adcRead(uint8_t pin)
             break;
     }
 
+    portEXIT_CRITICAL(&spinlock);
+
     // return value
     return value;
 }
@@ -128,6 +136,10 @@ uint16_t IRAM_ATTR adcRead(uint8_t pin)
 
     // variable to hold the ADC value
     uint16_t value = 0;
+
+    //Protects against core migration, on single core chips this is noop.
+    portENTER_CRITICAL(&spinlock);
+
     // do the ADC conversion
     switch(adc_num){
         case 1:
@@ -154,6 +166,8 @@ uint16_t IRAM_ATTR adcRead(uint8_t pin)
             break;
     }
 
+    portEXIT_CRITICAL(&spinlock);
+
     return value;
 }