81 lines
2.3 KiB
C
81 lines
2.3 KiB
C
#include "i2c.h"
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// Heavily inspired by: https://github.com/microchip-pic-avr-examples/avr128db48-bare-metal-twi-mplab/blob/master/twi-client.X/peripherals/TWI/TWI_client.c
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void init_i2c(void) {
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// Pin setup
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PORTA.DIRSET = PIN2_bm | PIN3_bm;
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PORTA.PINCTRLUPD = PIN2_bm | PIN3_bm;
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// Enable operating in debug
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TWI0.DBGCTRL = TWI_DBGRUN_bm;
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// Initialize the control A register
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TWI0.CTRLA = TWI_INPUTLVL_I2C_gc // I2C voltage transition level
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| TWI_SDASETUP_4CYC_gc // Four clock cycles setup time
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| TWI_SDAHOLD_50NS_gc // 50ns SDA hold time
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| TWI_FMPEN_OFF_gc // Standard SPI timing
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;
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// The device's slave address
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TWI0.SADDR = 0x42;
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// Enable acting as a slave
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TWI0.SCTRLA = TWI_DIEN_bm // Enable data interrupt
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| TWI_APIEN_bm // Enable more interrupts
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| TWI_PIEN_bm // Enable stop flag interrupt
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| PIN2_bm // Respond to all TWI addresses
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| TWI_ENABLE_bm // Enable acting as a slave
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;
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}
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// TODO: Figure out which interrupt does what
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void i2c_write_handler(uint8_t data) {
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printf("%u\n", data);
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}
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void i2c_read_handler() {
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printf("Master wanted to read.\n");
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}
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void i2c_stop_handler() {
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printf("Stop, I guess\n");
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}
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// Address received
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ISR(TWI0_TWIS_vect) {
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// Check for the data interrupt flag
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if (TWI0.SSTATUS & TWI_DIF_bm) {
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uint8_t data = 0;
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if ( ((TWI0.SSTATUS & TWI_DIR_bm) >> TWI_DIR_bp) == 0 ) {
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// Data write Master -> Slave
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data = TWI0.SDATA;
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// Send the data to the write handler
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i2c_write_handler(data);
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} else {
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// Data read Master <- Slave
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i2c_read_handler();
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data = TWI0.SDATA;
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}
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// Acknowledge having received
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TWI0.SCTRLB = TWI_ACKACT_ACK_gc | TWI_SCMD_RESPONSE_gc;
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}
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// Check for address match or STOP
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if (TWI0.SSTATUS & TWI_APIF_bm) {
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if (TWI0.SSTATUS & TWI_AP_ADR_gc) {
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// Address match, just send ack
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TWI0.SCTRLB = TWI_ACKACT_ACK_gc | TWI_SCMD_RESPONSE_gc;
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} else {
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// STOP condition received
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i2c_stop_handler();
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// Send ACK
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TWI0.SCTRLB = TWI_ACKACT_ACK_gc | TWI_SCMD_RESPONSE_gc;
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}
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}
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} |