Expand analogRead

adc/adc.ino

+#include "wiring_private.h"
+
 #define LED_GREEN 23
 #define SENSE_LINE_0 2
 
 int value;
 
+// Note that these values need to be kept in sync with the originals in analog_wiring.c.
+static int _readResolution = 10;
+static int _ADCResolution = 10;
+
+// Wait for synchronization of registers between the clock domains
+static __inline__ void syncADC() __attribute__((always_inline, unused));
+static void syncADC() { while ( ADC->STATUS.bit.SYNCBUSY == 1 ); }
+
+static inline uint32_t mapResolution(uint32_t value, uint32_t from, uint32_t to)
+{
+    if (from == to) {
+        return value;
+    }
+    if (from > to) {
+        return value >> (from-to);
+    }
+    return value << (to-from);
+}
+
+
+uint32_t bm_analogRead( uint32_t pin )
+{
+    uint32_t valueRead = 0;
+
+    // Uses a variable outside this translation unit
+    //if (!ADCinitialized) {
+    //    initADC();
+    //}
+
+    #if defined(REMAP_ANALOG_PIN_ID)
+    REMAP_ANALOG_PIN_ID(pin);
+    #endif
+
+    #if (SAMC21 || SAMD51)
+    Adc* ADC;
+    if ( (g_APinDescription[pin].ulPeripheralAttribute & PER_ATTR_ADC_MASK) == PER_ATTR_ADC_ALT ) {
+        ADC = ADC1;
+    } else {
+        ADC = ADC0;
+    }
+    #endif
+
+    // pinPeripheral now handles disabling the DAC (if active)
+    if ( pinPeripheral(pin, PIO_ANALOG_ADC) == RET_STATUS_OK )
+    {
+        ADC->INPUTCTRL.bit.MUXPOS = GetADC(pin); // Selection for the positive ADC input
+
+        syncADC();
+
+        ADC->CTRLA.bit.ENABLE = 0x01;             // Enable ADC
+        syncADC();
+
+        // Start conversion
+        ADC->SWTRIG.bit.START = 1;
+        syncADC();
+
+        // Store the value
+        while (ADC->INTFLAG.bit.RESRDY == 0);   // Waiting for conversion to complete
+        valueRead = ADC->RESULT.reg;
+
+        ADC->CTRLA.bit.ENABLE = 0x00;             // Disable ADC
+        syncADC();
+    }
+
+    return mapResolution(valueRead, _ADCResolution, _readResolution);
+}
+
+
 void setup() {
     // put your setup code here, to run once:
     Serial.begin(9600);
     pinMode(LED_GREEN, OUTPUT);
+    // Calling the regular method once ensures that the ADC does get initialized.
+    analogRead(SENSE_LINE_0);
 }
 
 void loop() {
     // put your main code here, to run repeatedly:
-    value = analogRead(SENSE_LINE_0);
+    value = bm_analogRead(SENSE_LINE_0);
     Serial.println(value);
     delay(1000);
 }