adc/adc.ino

 #include "wiring_private.h"
 
 #define LED_GREEN 23
+#define CHARGE_LINE_0 14
 #define SENSE_LINE_0 2
 
 int value;
@@ -24,14 +25,36 @@ static inline uint32_t mapResolution(uint32_t value, uint32_t from, uint32_t to)
     return value << (to-from);
 }
 
+void init_pin_adc(uint32_t pin) {
+    uint8_t const pinPort = GetPort(pin);
+    uint8_t const pinNum = GetPin(pin);
+
+    // Preserve state of pullup/pulldown enable, clear the rest of the bits
+    uint8_t pinCfg = (PORT->Group[pinPort].PINCFG[pinNum].reg & PORT_PINCFG_PULLEN);
+
+    if ( pinNum & 1 ) // is pin odd?
+    {
+        // Get whole current setup for both odd and even pins and remove odd one, then set new muxing
+        uint32_t temp = (PORT->Group[pinPort].PMUX[pinNum >> 1].reg) & PORT_PMUX_PMUXE( 0xF ) ;
+        PORT->Group[pinPort].PMUX[pinNum >> 1].reg = temp|PORT_PMUX_PMUXO(PER_ANALOG) ;
+    }
+    else // even pin
+    {
+        // Get whole current setup for both odd and even pins and remove even one, then set new muxing
+        uint32_t temp = (PORT->Group[pinPort].PMUX[pinNum >> 1].reg) & PORT_PMUX_PMUXO( 0xF ) ;
+        PORT->Group[pinPort].PMUX[pinNum >> 1].reg = temp|PORT_PMUX_PMUXE(PER_ANALOG) ;
+    }
+
+    pinCfg |= PORT_PINCFG_PMUXEN; // Enable peripheral mux
+
+    // Set pin drive strength, enable/disable pull resistor, enable/disable INEN, and enable/disable the peripheral mux
+    PORT->Group[pinPort].PINCFG[pinNum].reg = (uint8_t)pinCfg ;
+}
 
 uint32_t bm_analogRead( uint32_t pin )
 {
     uint32_t valueRead = 0;
 
-    // pinPeripheral now handles disabling the DAC (if active)
-    if ( pinPeripheral(pin, PIO_ANALOG_ADC) == RET_STATUS_OK )
-    {
     // Start conversion
     ADC->SWTRIG.bit.START = 1;
     syncADC();
@@ -39,20 +62,24 @@ uint32_t bm_analogRead( uint32_t pin )
     // Store the value
     while (ADC->INTFLAG.bit.RESRDY == 0);   // Waiting for conversion to complete
     valueRead = ADC->RESULT.reg;
-    }
 
     return mapResolution(valueRead, _ADCResolution, _readResolution);
 }
 
 
 void setup() {
-    // put your setup code here, to run once:
     Serial.begin(9600);
     pinMode(LED_GREEN, OUTPUT);
+    pinMode(CHARGE_LINE_0, OUTPUT);
+    digitalWrite(CHARGE_LINE_0, LOW);
 
     // Initialize the ADC
     initADC();
 
+    // Everything seems to function if I don't do this, but I'm leaving it in until I have a chance
+    // to investigate what's happening.
+    init_pin_adc(SENSE_LINE_0);
+
     // Selection for the positive ADC input
     ADC->INPUTCTRL.bit.MUXPOS = GetADC(SENSE_LINE_0);
     syncADC();
@@ -63,8 +90,15 @@ void setup() {
 }
 
 void loop() {
-    // put your main code here, to run repeatedly:
+    digitalWrite(CHARGE_LINE_0, LOW);
+    delay(1000);
+
     value = bm_analogRead(SENSE_LINE_0);
     Serial.println(value);
+
+    digitalWrite(CHARGE_LINE_0, HIGH);
     delay(1000);
+
+    value = bm_analogRead(SENSE_LINE_0);
+    Serial.println(value);
 }