akutester/soft/ads1224.c

#include "ads1224.h"
#include "main.h"

volatile unsigned char ads1224_read_wait = 0;
volatile float adc_val;
volatile unsigned char adc_data_ready;

void ads1224_mux(unsigned char input){
	if(input&1){
		PORTB |= ADC_MUX0;
	} else {
		PORTB &= ~ADC_MUX0;
	}
	if(input&2){
		PORTB |= ADC_MUX1;
	} else {
		PORTB &= ~ADC_MUX1;
	}
}

void ads1224_init(void){
	// configure pin change interrupt on PB6/PCINT14
	PCICR |= _BV(PCIE1);
	PCMSK1 |= _BV(PCINT14);
	
	// configure mux outputs
	DDRB |= ADC_MUX1 | ADC_MUX0; // MUX1 is SS so set it before SPI init!
	
	// configure SPI
	DDRB |= _BV(PB7); // SCK as output
	SPCR = _BV(SPE) | _BV(MSTR) | _BV(CPHA);
	SPSR = _BV(SPI2X); // CLK/2
	
	ads1224_read_wait = 1;
}

void ads1224_data_read(void){
	static unsigned char avg_count = 0;
	static signed long int buf = 0;
	unsigned char i;
	union {
		signed long int out;
		unsigned char d[4];
	} ads1224_out;
	
	for(i=3; i>0; i--){
		while(!(SPSR & _BV(SPIF)));
		if(i > 1)
			SPDR = 0;
		ads1224_out.d[i] = SPDR;
	}
	
	SPCR = 0; // addidtional sck pulse
	PORTB |= _BV(PB7);
	PORTB &= ~_BV(PB7);
	SPCR = _BV(SPE) | _BV(MSTR) | _BV(CPHA);
	
	buf += ads1224_out.out >> 8;
	if(++avg_count == 32){
		adc_val = buf; // interrupt context!
		avg_count = 0;
		buf = 0;
		adc_data_ready = 1;
	}
	
	ads1224_read_wait = 1;
}

ISR(PCINT1_vect){
	PORTB ^= _BV(PB2);
	if(ads1224_read_wait && !(PINB & _BV(PB6))){
		ads1224_read_wait = 0;
		SPDR = 0; // start SPI transaction
		ads1224_data_read();
	}
	PORTB ^= _BV(PB2);
}