Merge pull request #25 from Lincoln-Agritech/master

Add support for ADC wakeup interrupt on SAMD21

examples/AdcWakeup/AdcWakeup.ino

@@ -0,0 +1,61 @@
+/*
+  AdcWakeup
+
+  This sketch demonstrates the usage of the ADC to wakeup a chip in sleep mode.
+  Sleep modes allow a significant drop in the power usage of a board while it does nothing waiting for an event to happen. Battery powered application can take advantage of these modes to enhance battery life significantly.
+
+  In this sketch, changing the voltage on pin A0 will wake up the board. You can test this by connecting a potentiometer between VCC, A0, and GND.
+  Please note that, if the processor is sleeping, a new sketch can't be uploaded. To overcome this, manually reset the board (usually with a single or double tap to the RESET button)
+
+  This example code is in the public domain.
+*/
+
+#include "ArduinoLowPower.h"
+
+// Blink sequence number
+// Declare it volatile since it's incremented inside an interrupt
+volatile int repetitions = 1;
+
+// Pin used to trigger a wakeup
+const int pin = A0;
+// How sensitive to be to changes in voltage
+const int margin = 10;
+
+void setup() {
+  pinMode(LED_BUILTIN, OUTPUT);
+  pinMode(pin, INPUT);
+}
+
+void loop() {
+  for (int i = 0; i < repetitions; i++) {
+    digitalWrite(LED_BUILTIN, HIGH);
+    delay(500);
+    digitalWrite(LED_BUILTIN, LOW);
+    delay(500);
+  }
+
+  // Read the voltage at the ADC pin
+  int value = analogRead(pin);
+
+  // Define a window around that value
+  uint16_t lo = max(value - margin, 0);
+  uint16_t hi = min(value + margin, UINT16_MAX); 
+
+  // Attach an ADC interrupt on pin A0, calling repetitionsIncrease when the voltage is outside the given range.
+  // This should be called immediately before LowPower.sleep() because it reconfigures the ADC internally.
+  LowPower.attachAdcInterrupt(pin, repetitionsIncrease, ADC_INT_OUTSIDE, lo, hi);
+
+  // Triggers an infinite sleep (the device will be woken up only by the registered wakeup sources)
+  // The power consumption of the chip will drop consistently
+  LowPower.sleep();
+
+  // Detach the ADC interrupt. This should be called immediately after LowPower.sleep() because it restores the ADC configuration after waking up.
+  LowPower.detachAdcInterrupt();
+}
+
+void repetitionsIncrease() {
+  // This function will be called once on device wakeup
+  // You can do some little operations here (like changing variables which will be used in the loop)
+  // Remember to avoid calling delay() and long running functions since this functions executes in interrupt context
+  repetitions ++;
+}

src/ArduinoLowPower.h

@@ -28,6 +28,16 @@ typedef enum{
 	ANALOG_COMPARATOR_WAKEUP = 3
 } wakeup_reason;
 
+#ifdef ARDUINO_ARCH_SAMD
+enum adc_interrupt
+{
+	ADC_INT_BETWEEN,
+	ADC_INT_OUTSIDE,
+	ADC_INT_ABOVE_MIN,
+	ADC_INT_BELOW_MAX,
+};
+#endif
+
 
 class ArduinoLowPowerClass {
 	public:
@@ -68,10 +78,17 @@ class ArduinoLowPowerClass {
 		wakeup_reason wakeupReason();
 		#endif
 
+		#ifdef ARDUINO_ARCH_SAMD
+		void attachAdcInterrupt(uint32_t pin, voidFuncPtr callback, adc_interrupt mode, uint16_t lo, uint16_t hi);
+		void detachAdcInterrupt();
+		#endif
+
 	private:
 		void setAlarmIn(uint32_t millis);
 		#ifdef ARDUINO_ARCH_SAMD
 		RTCZero rtc;
+		voidFuncPtr adc_cb;
+		friend void ADC_Handler();
 		#endif
 		#ifdef BOARD_HAS_COMPANION_CHIP
 		void (*companionSleepCB)(bool);

src/samd/ArduinoLowPower.cpp

@@ -3,6 +3,27 @@
 #include "ArduinoLowPower.h"
 #include "WInterrupts.h"
 
+static void configGCLK6()
+{
+	// enable EIC clock
+	GCLK->CLKCTRL.bit.CLKEN = 0; //disable GCLK module
+	while (GCLK->STATUS.bit.SYNCBUSY);
+
+	GCLK->CLKCTRL.reg = (uint16_t) (GCLK_CLKCTRL_CLKEN | GCLK_CLKCTRL_GEN_GCLK6 | GCLK_CLKCTRL_ID( GCM_EIC )) ;  //EIC clock switched on GCLK6
+	while (GCLK->STATUS.bit.SYNCBUSY);
+
+	GCLK->GENCTRL.reg = (GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_OSCULP32K | GCLK_GENCTRL_ID(6));  //source for GCLK6 is OSCULP32K
+	while (GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY);
+
+	GCLK->GENCTRL.bit.RUNSTDBY = 1;  //GCLK6 run standby
+	while (GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY);
+
+	/* Errata: Make sure that the Flash does not power all the way down
+     	* when in sleep mode. */
+
+	NVMCTRL->CTRLB.bit.SLEEPPRM = NVMCTRL_CTRLB_SLEEPPRM_DISABLED_Val;
+}
+
 void ArduinoLowPowerClass::idle() {
 	SCB->SCR &= ~SCB_SCR_SLEEPDEEP_Msk;
 	PM->SLEEP.reg = 2;
@@ -80,26 +101,117 @@ void ArduinoLowPowerClass::attachInterruptWakeup(uint32_t pin, voidFuncPtr callb
 	//pinMode(pin, INPUT_PULLUP);
 	attachInterrupt(pin, callback, mode);
 
-	// enable EIC clock
+	configGCLK6();
-	GCLK->CLKCTRL.bit.CLKEN = 0; //disable GCLK module
-	while (GCLK->STATUS.bit.SYNCBUSY);
-
-	GCLK->CLKCTRL.reg = (uint16_t) (GCLK_CLKCTRL_CLKEN | GCLK_CLKCTRL_GEN_GCLK6 | GCLK_CLKCTRL_ID( GCM_EIC )) ;  //EIC clock switched on GCLK6
-	while (GCLK->STATUS.bit.SYNCBUSY);
-
-	GCLK->GENCTRL.reg = (GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_OSCULP32K | GCLK_GENCTRL_ID(6));  //source for GCLK6 is OSCULP32K
-	while (GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY);
-
-	GCLK->GENCTRL.bit.RUNSTDBY = 1;  //GCLK6 run standby
-	while (GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY);
 
 	// Enable wakeup capability on pin in case being used during sleep
 	EIC->WAKEUP.reg |= (1 << in);
+}
 
-	/* Errata: Make sure that the Flash does not power all the way down
+void ArduinoLowPowerClass::attachAdcInterrupt(uint32_t pin, voidFuncPtr callback, adc_interrupt mode, uint16_t lo, uint16_t hi)
-     	* when in sleep mode. */
+{
+	uint8_t winmode = 0;
 
-	NVMCTRL->CTRLB.bit.SLEEPPRM = NVMCTRL_CTRLB_SLEEPPRM_DISABLED_Val;
+	switch (mode) {
+		case ADC_INT_BETWEEN:   winmode = ADC_WINCTRL_WINMODE_MODE3; break;
+		case ADC_INT_OUTSIDE:   winmode = ADC_WINCTRL_WINMODE_MODE4; break;
+		case ADC_INT_ABOVE_MIN: winmode = ADC_WINCTRL_WINMODE_MODE1; break;
+		case ADC_INT_BELOW_MAX: winmode = ADC_WINCTRL_WINMODE_MODE2; break;
+		default: return;
+	}
+
+	adc_cb = callback;
+
+	configGCLK6();
+
+	// Configure ADC to use GCLK6 (OSCULP32K)
+	while (GCLK->STATUS.bit.SYNCBUSY) {}
+	GCLK->CLKCTRL.reg = GCLK_CLKCTRL_ID_ADC
+						| GCLK_CLKCTRL_GEN_GCLK6
+						| GCLK_CLKCTRL_CLKEN;
+	while (GCLK->STATUS.bit.SYNCBUSY) {}
+
+	// Set ADC prescaler as low as possible
+	ADC->CTRLB.bit.PRESCALER = ADC_CTRLB_PRESCALER_DIV4;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Configure window mode
+	ADC->WINLT.reg = lo;
+	ADC->WINUT.reg = hi;
+	ADC->WINCTRL.reg = winmode;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Enable window interrupt
+	ADC->INTENSET.bit.WINMON = 1;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Enable ADC in standby mode
+	ADC->CTRLA.bit.RUNSTDBY = 1;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Enable continuous conversions
+	ADC->CTRLB.bit.FREERUN = 1;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Configure input mux
+	ADC->INPUTCTRL.bit.MUXPOS = g_APinDescription[pin].ulADCChannelNumber;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Enable the ADC
+	ADC->CTRLA.bit.ENABLE = 1;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Start continuous conversions
+	ADC->SWTRIG.bit.START = 1;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Enable the ADC interrupt
+	NVIC_EnableIRQ(ADC_IRQn);
+}
+
+void ArduinoLowPowerClass::detachAdcInterrupt()
+{
+	// Disable the ADC interrupt
+	NVIC_DisableIRQ(ADC_IRQn);
+
+	// Disable the ADC
+	ADC->CTRLA.bit.ENABLE = 0;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Disable continuous conversions
+	ADC->CTRLB.bit.FREERUN = 0;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Disable ADC in standby mode
+	ADC->CTRLA.bit.RUNSTDBY = 1;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Disable window interrupt
+	ADC->INTENCLR.bit.WINMON = 1;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Disable window mode
+	ADC->WINCTRL.reg = ADC_WINCTRL_WINMODE_DISABLE;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Restore ADC prescaler
+	ADC->CTRLB.bit.PRESCALER = ADC_CTRLB_PRESCALER_DIV512_Val;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Restore ADC clock
+	while (GCLK->STATUS.bit.SYNCBUSY) {}
+	GCLK->CLKCTRL.reg = GCLK_CLKCTRL_ID_ADC
+						| GCLK_CLKCTRL_GEN_GCLK0
+						| GCLK_CLKCTRL_CLKEN;
+	while (GCLK->STATUS.bit.SYNCBUSY) {}
+
+	adc_cb = nullptr;
+}
+
+void ADC_Handler()
+{
+	// Clear the interrupt flag
+	ADC->INTFLAG.bit.WINMON = 1;
+	LowPower.adc_cb();
 }
 
 ArduinoLowPowerClass LowPower;