MSP430FR5994 ADC: add asynchronous backgorund readings on P3.0

#ifndef ADC_H

#define ADC_H

#include <stddef.h>

#include <stdint.h>

class ADC {

	private:

		ADC(ADC const &copy);

		uint16_t bufsize;

		uint16_t bufpos;

		uint16_t *buf16;

		uint8_t *buf8;

		volatile bool bufferFull;

	public:

		ADC() {}

		ADC() : bufsize(0), bufpos(0), buf16(NULL), buf8(NULL), bufferFull(false) {}

		float getTemp();

		float getVCC();

		uint16_t getReading();

		void startSampling(uint16_t *buf, uint16_t bufsize);

		void stopSampling();

		inline bool doneSampling()

		{

			if (bufferFull) {

				bufferFull = false;

				return true;

			}

			return false;

		}

		inline void storeReading(uint16_t value)

		{

			buf16[bufpos++] = value;

			bufpos %= bufsize;

			if (bufpos == 0) {

				bufferFull = true;

			}

		}

};

extern ADC adc;

#define CALADC12_12V_30C  *((unsigned int *)0x1A1A)

#define CALADC12_12V_85C  *((unsigned int *)0x1A1C)

/*

 * Obtain a single reading of the embedded temperature sensor, converted to °C.

 * Configures and enables ADC and voltage reference, reads the temperature, and then disables both.

 * This is a blocking function.

 */

float ADC::getTemp()

{

	float ret;

	return ret;

}

/*

 * Obtain a single VCC reading, using the internal 2V voltage reference and the internal VCC/2 rail.

 * Configures and enables ADC and voltage reference, reads the temperature, and then disables both.

 * This is a blocking function.

 */

float ADC::getVCC()

{

	float ret;

	return ret;

}

/*

 * Obtain a single 12-bit reading of A12 (P3.0), using AVCC / AVSS as references.

 * Configures and enables the ADC, reads a single value, and then disables the ADC again.

 * This is a blocking function.

 */

uint16_t ADC::getReading()

{

	ADC12CTL0 &= ~ADC12ENC; // disable ADC for configuration

	ADC12CTL0 = ADC12SHT0_8 | ADC12SHT1_8 | ADC12ON; // Sample & Hold: 64 ADC12CLK cycles; enable ADC

	ADC12CTL0 = ADC12SHT0_8 | ADC12SHT1_8 | ADC12ON; // Sample & Hold: 256 ADC12CLK cycles; enable ADC

	ADC12CTL1 = ADC12SHP; // MODOSC, no prescaler

	ADC12CTL2 = ADC12RES_2; // 12 bit resolution

	ADC12CTL3 = ADC12CSTARTADD_0; // store reading in ADCMEM0

	return ret;

}

/*

 * Obtain a serias of 12-bit readings of A12 (P3.0), using AVCC / AVSS as references.

 * Configures and enables the ADC, and then returns.

 */

void ADC::startSampling(uint16_t *buf, uint16_t bufsize)

{

	ADC12CTL0 &= ~ADC12ENC; // disable ADC for configuration

	ADC12CTL0 = ADC12SHT0_8 | ADC12SHT1_8 | ADC12MSC | ADC12ON; // Sample & Hold: 64 ADC12CLK cycles; multiple conversions; enable ADC

	/*

	 * Sample & Hold: 64 ADC12CLK cycles

	 * 8-bit reading: 10 ADC12CLK cycles

	 * → 74 ADC12CLK cycles per reading

	 * → ≈68 kHz sample rate at ≈5 MHz

	 * 216,216 Hz / 2048 == 106 Hz (close enough)

	 * → set prescalers to /2048 (or something close, anyways)

	 * ... lowest we can get with SMCLK ref is /512, that's fine too

	 * Also, we want repeated single-channel conversion.

	 */

	ADC12CTL1 = ADC12PDIV__64 | ADC12SHP | ADC12DIV_7 | ADC12SSEL_3 | ADC12CONSEQ_2;

	// 12 bit readings (14 clock cycles conversion time)

	// (10 bit → 12 cycles / 12 bit → 14 cycles)

	ADC12CTL2 = ADC12RES_2;

	// store each (consecutive) reading in ADCMEM1

	ADC12CTL3 = ADC12CSTARTADD_1;

	// use default reference (AVSS / AVCC) (only required if changed by some other runtime code beforehand)

	// read from A12 (P3.0)

	ADC12MCTL1 = ADC12INCH_12;

	// disable output driver and input schmitt triggers on P3.0 (A12)

	P3SEL0 |= BIT0;

	P3SEL1 |= BIT0;

	// raise an interrupt after each sample

	ADC12IER0 = ADC12IE1;

	ADC12IFGR0 = ADC12IFG1;

	// clear pending interrupts

	ADC12IV = 0;

	buf16 = buf;

	this->bufsize = bufsize;

	ADC12CTL0 |= ADC12ENC | ADC12SC;

}

void ADC::stopSampling()

{

	ADC12CTL0 &= ~ADC12ENC; // disable any conversion to allow ADC configuration

	ADC12CTL0 &= ~ADC12ON; // Turn off ADC

}

ADC adc;

#ifndef __acweaving

__attribute__((interrupt(ADC12_VECTOR))) void handle_adc_irq()

{

	if (ADC12IV == 0x00e) {

		// ADC12MEM1

		adc.storeReading(ADC12MEM1);

	}

}

#endif