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281 lines
6.5 KiB
281 lines
6.5 KiB
/*
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* WARNING: be careful changing this code, it is very timing dependent
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*/
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#ifndef F_CPU
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#define F_CPU 16000000
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#endif
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include <util/delay.h>
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#include <stdbool.h>
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#include "serial.h"
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#ifndef USE_I2C
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#ifndef SOFT_SERIAL_PIN
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#error quantum/split_common/serial.c need SOFT_SERIAL_PIN define
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#endif
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#ifdef __AVR_ATmega32U4__
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// if using ATmega32U4 I2C, can not use PD0 and PD1 in soft serial.
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#ifdef USE_I2C
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#if SOFT_SERIAL_PIN == D0 || SOFT_SERIAL_PIN == D1
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#error Using ATmega32U4 I2C, so can not use PD0, PD1
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#endif
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#endif
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#if SOFT_SERIAL_PIN >= D0 && SOFT_SERIAL_PIN <= D3
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#define SERIAL_PIN_DDR DDRD
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#define SERIAL_PIN_PORT PORTD
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#define SERIAL_PIN_INPUT PIND
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#if SOFT_SERIAL_PIN == D0
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#define SERIAL_PIN_MASK _BV(PD0)
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#define EIMSK_BIT _BV(INT0)
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#define EICRx_BIT (~(_BV(ISC00) | _BV(ISC01)))
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#define SERIAL_PIN_INTERRUPT INT0_vect
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#elif SOFT_SERIAL_PIN == D1
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#define SERIAL_PIN_MASK _BV(PD1)
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#define EIMSK_BIT _BV(INT1)
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#define EICRx_BIT (~(_BV(ISC10) | _BV(ISC11)))
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#define SERIAL_PIN_INTERRUPT INT1_vect
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#elif SOFT_SERIAL_PIN == D2
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#define SERIAL_PIN_MASK _BV(PD2)
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#define EIMSK_BIT _BV(INT2)
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#define EICRx_BIT (~(_BV(ISC20) | _BV(ISC21)))
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#define SERIAL_PIN_INTERRUPT INT2_vect
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#elif SOFT_SERIAL_PIN == D3
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#define SERIAL_PIN_MASK _BV(PD3)
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#define EIMSK_BIT _BV(INT3)
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#define EICRx_BIT (~(_BV(ISC30) | _BV(ISC31)))
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#define SERIAL_PIN_INTERRUPT INT3_vect
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#endif
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#elif SOFT_SERIAL_PIN == E6
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#define SERIAL_PIN_DDR DDRE
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#define SERIAL_PIN_PORT PORTE
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#define SERIAL_PIN_INPUT PINE
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#define SERIAL_PIN_MASK _BV(PE6)
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#define EIMSK_BIT _BV(INT6)
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#define EICRx_BIT (~(_BV(ISC60) | _BV(ISC61)))
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#define SERIAL_PIN_INTERRUPT INT6_vect
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#else
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#error invalid SOFT_SERIAL_PIN value
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#endif
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#else
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#error serial.c now support ATmega32U4 only
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#endif
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// Serial pulse period in microseconds. Its probably a bad idea to lower this
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// value.
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#define SERIAL_DELAY 24
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uint8_t volatile serial_slave_buffer[SERIAL_SLAVE_BUFFER_LENGTH] = {0};
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uint8_t volatile serial_master_buffer[SERIAL_MASTER_BUFFER_LENGTH] = {0};
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#define SLAVE_DATA_CORRUPT (1<<0)
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volatile uint8_t status = 0;
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inline static
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void serial_delay(void) {
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_delay_us(SERIAL_DELAY);
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}
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inline static
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void serial_output(void) {
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SERIAL_PIN_DDR |= SERIAL_PIN_MASK;
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}
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// make the serial pin an input with pull-up resistor
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inline static
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void serial_input(void) {
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SERIAL_PIN_DDR &= ~SERIAL_PIN_MASK;
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SERIAL_PIN_PORT |= SERIAL_PIN_MASK;
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}
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inline static
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uint8_t serial_read_pin(void) {
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return !!(SERIAL_PIN_INPUT & SERIAL_PIN_MASK);
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}
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inline static
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void serial_low(void) {
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SERIAL_PIN_PORT &= ~SERIAL_PIN_MASK;
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}
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inline static
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void serial_high(void) {
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SERIAL_PIN_PORT |= SERIAL_PIN_MASK;
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}
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void serial_master_init(void) {
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serial_output();
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serial_high();
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}
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void serial_slave_init(void) {
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serial_input();
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// Enable INT0
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EIMSK |= _BV(INT0);
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// Trigger on falling edge of INT0
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EICRA &= ~(_BV(ISC00) | _BV(ISC01));
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}
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// Used by the master to synchronize timing with the slave.
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static
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void sync_recv(void) {
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serial_input();
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// This shouldn't hang if the slave disconnects because the
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// serial line will float to high if the slave does disconnect.
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while (!serial_read_pin());
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serial_delay();
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}
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// Used by the slave to send a synchronization signal to the master.
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static
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void sync_send(void) {
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serial_output();
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serial_low();
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serial_delay();
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serial_high();
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}
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// Reads a byte from the serial line
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static
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uint8_t serial_read_byte(void) {
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uint8_t byte = 0;
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serial_input();
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for ( uint8_t i = 0; i < 8; ++i) {
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byte = (byte << 1) | serial_read_pin();
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serial_delay();
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_delay_us(1);
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}
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return byte;
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}
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// Sends a byte with MSB ordering
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static
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void serial_write_byte(uint8_t data) {
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uint8_t b = 8;
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serial_output();
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while( b-- ) {
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if(data & (1 << b)) {
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serial_high();
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} else {
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serial_low();
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}
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serial_delay();
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}
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}
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// interrupt handle to be used by the slave device
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ISR(SERIAL_PIN_INTERRUPT) {
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sync_send();
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uint8_t checksum = 0;
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for (int i = 0; i < SERIAL_SLAVE_BUFFER_LENGTH; ++i) {
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serial_write_byte(serial_slave_buffer[i]);
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sync_send();
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checksum += serial_slave_buffer[i];
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}
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serial_write_byte(checksum);
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sync_send();
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// wait for the sync to finish sending
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serial_delay();
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// read the middle of pulses
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_delay_us(SERIAL_DELAY/2);
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uint8_t checksum_computed = 0;
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for (int i = 0; i < SERIAL_MASTER_BUFFER_LENGTH; ++i) {
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serial_master_buffer[i] = serial_read_byte();
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sync_send();
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checksum_computed += serial_master_buffer[i];
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}
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uint8_t checksum_received = serial_read_byte();
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sync_send();
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serial_input(); // end transaction
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if ( checksum_computed != checksum_received ) {
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status |= SLAVE_DATA_CORRUPT;
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} else {
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status &= ~SLAVE_DATA_CORRUPT;
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}
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}
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inline
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bool serial_slave_DATA_CORRUPT(void) {
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return status & SLAVE_DATA_CORRUPT;
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}
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// Copies the serial_slave_buffer to the master and sends the
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// serial_master_buffer to the slave.
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//
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// Returns:
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// 0 => no error
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// 1 => slave did not respond
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int serial_update_buffers(void) {
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// this code is very time dependent, so we need to disable interrupts
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cli();
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// signal to the slave that we want to start a transaction
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serial_output();
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serial_low();
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_delay_us(1);
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// wait for the slaves response
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serial_input();
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serial_high();
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_delay_us(SERIAL_DELAY);
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// check if the slave is present
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if (serial_read_pin()) {
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// slave failed to pull the line low, assume not present
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sei();
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return 1;
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}
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// if the slave is present syncronize with it
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sync_recv();
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uint8_t checksum_computed = 0;
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// receive data from the slave
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for (int i = 0; i < SERIAL_SLAVE_BUFFER_LENGTH; ++i) {
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serial_slave_buffer[i] = serial_read_byte();
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sync_recv();
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checksum_computed += serial_slave_buffer[i];
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}
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uint8_t checksum_received = serial_read_byte();
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sync_recv();
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if (checksum_computed != checksum_received) {
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sei();
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return 1;
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}
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uint8_t checksum = 0;
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// send data to the slave
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for (int i = 0; i < SERIAL_MASTER_BUFFER_LENGTH; ++i) {
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serial_write_byte(serial_master_buffer[i]);
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sync_recv();
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checksum += serial_master_buffer[i];
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}
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serial_write_byte(checksum);
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sync_recv();
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// always, release the line when not in use
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serial_output();
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serial_high();
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sei();
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return 0;
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}
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#endif
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