i2c_driver.cpp

#include "i2c_driver.h"
#include "twi.h"
#include "board.h"
#include "stdlib.h"

#define I2C_CLK_FAST  400000

uint32_t fromBCD(uint8_t bcd_value) {
	return (((bcd_value & 0xF0) * 10) >> 4) + (bcd_value & 0x0F);
}

uint8_t toBCD(uint32_t value) {
	div_t qr = div(value, 10);
	return (qr.quot << 4) + qr.rem;
}

twi_packet getPacket(uint8_t chip, uint8_t* addr, uint8_t addr_len, uint8_t *buffer, uint32_t length)
{
	twi_packet packet;
	packet.chip = chip;
	for(uint8_t i=0; i < addr_len; ++i)
		packet.addr[i] = addr[i];
	packet.addr_length = addr_len;
	packet.buffer = buffer;
	packet.length = length;
	return packet;
}

bool i2cInit()
{
	//Enable Peripheral Clock
	PMC->PMC_PCER0 |= 0x00080000L ;
	//Enable TWI PIOs
	register Pio *pioptr;
	pioptr = PIOA ;
	pioptr->PIO_ABCDSR[0] &= ~0x00000018 ;        // Peripheral A
	pioptr->PIO_ABCDSR[1] &= ~0x00000018 ;        // Peripheral A
	pioptr->PIO_PDR = 0x00000018 ;                                        // Assign to peripheral

	twi_enable_master_mode(TWI0);
	twi_options_t opt;
	opt.master_clk = Master_frequency;
	opt.speed = I2C_CLK_FAST;
	return twi_master_init(TWI0, &opt) == TWI_SUCCESS;
}

void i2cCheck(){};

uint32_t i2cReadBuffer(uint8_t chip, uint8_t* addr, uint8_t addr_len, uint8_t *buffer, uint32_t length)
{
	twi_packet packet(
			getPacket(chip, addr, addr_len, buffer, length)
		);
	return twi_master_read(TWI0, &packet);
}

bool i2cWriteBuffer(uint8_t chip, uint8_t* addr, uint8_t addr_len, uint8_t *buffer, uint32_t length)
{
	twi_packet packet(
			getPacket(chip, addr, addr_len, buffer, length)
		);
	return twi_master_write(TWI0, &packet) == TWI_SUCCESS;
}

rtc_ds3231.cpp

#include "opentx.h"
#include "i2c_driver.h"
#include "twi.h"

#define DS3231_I2C_ADDR 0x68

int8_t volumeRequired; //HACK ALERT!

void readExtRtc() {
	uint8_t buffer[7];
	gtm utm;
	int res =  i2cReadBuffer(DS3231_I2C_ADDR, 0, 2, buffer, 7);
	if(res != TWI_SUCCESS) {
		gtm utm;
		utm.tm_sec = 0;
		utm.tm_min = 0;
		utm.tm_hour = 0;
		utm.tm_mday = 0;
		utm.tm_mon = 1;
		utm.tm_year = res + 100;
		g_rtcTime = gmktime(&utm);
	} else {
		// Set the date and time
		utm.tm_sec = fromBCD(buffer[0] & 0x7F);
		utm.tm_min = fromBCD(buffer[1] & 0x7F);
		utm.tm_hour = fromBCD(buffer[2] & 0x3F);
		utm.tm_mday = fromBCD(buffer[4] & 0x3F);
		utm.tm_mon = fromBCD(buffer[5] & 0x1F) - 1;
		utm.tm_year = fromBCD(buffer[6]) + 100;
	}
	g_rtcTime = gmktime(&utm);
}

void writeExtRtc(gtm* ptr) {
	g_rtcTime = gmktime(ptr);
	uint8_t buffer[7];

	buffer[0] = toBCD(ptr->tm_sec);
	buffer[1] = toBCD(ptr->tm_min);
	buffer[2] = toBCD(ptr->tm_hour);
	buffer[3] = toBCD(ptr->tm_wday);
	buffer[4] = toBCD(ptr->tm_mday);
	buffer[5] = toBCD(ptr->tm_mon + 1);
	uint8_t offset = ptr->tm_year >= 100 ? 100 : 0;
	buffer[6] = toBCD(ptr->tm_year - offset);
	i2cWriteBuffer(DS3231_I2C_ADDR, 0, 1, buffer, 7);
}

void rtcSetTime(struct gtm * t) {
	writeExtRtc(t);
}

void rtcInit() {
	readExtRtc();
}