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Diffstat (limited to 'keyboards/ergoinu/serial.c')
| -rw-r--r-- | keyboards/ergoinu/serial.c | 295 |
1 files changed, 295 insertions, 0 deletions
diff --git a/keyboards/ergoinu/serial.c b/keyboards/ergoinu/serial.c new file mode 100644 index 0000000000..5919415877 --- /dev/null +++ b/keyboards/ergoinu/serial.c @@ -0,0 +1,295 @@ +/* + * WARNING: be careful changing this code, it is very timing dependent + */ + +#ifndef F_CPU +#define F_CPU 16000000 +#endif + +#include <avr/io.h> +#include <avr/interrupt.h> +#include <util/delay.h> +#include <stdbool.h> +#include "serial.h" + +#ifdef USE_SERIAL + +#define _delay_sub_us(x) __builtin_avr_delay_cycles(x) + +// Serial pulse period in microseconds. +#define SELECT_SERIAL_SPEED 1 +#if SELECT_SERIAL_SPEED == 0 + // Very High speed + #define SERIAL_DELAY 4 // micro sec + #define READ_WRITE_START_ADJUST 30 // cycles + #define READ_WRITE_WIDTH_ADJUST 10 // cycles +#elif SELECT_SERIAL_SPEED == 1 + // High speed + #define SERIAL_DELAY 6 // micro sec + #define READ_WRITE_START_ADJUST 23 // cycles + #define READ_WRITE_WIDTH_ADJUST 10 // cycles +#elif SELECT_SERIAL_SPEED == 2 + // Middle speed + #define SERIAL_DELAY 12 // micro sec + #define READ_WRITE_START_ADJUST 25 // cycles + #define READ_WRITE_WIDTH_ADJUST 10 // cycles +#elif SELECT_SERIAL_SPEED == 3 + // Low speed + #define SERIAL_DELAY 24 // micro sec + #define READ_WRITE_START_ADJUST 25 // cycles + #define READ_WRITE_WIDTH_ADJUST 10 // cycles +#elif SELECT_SERIAL_SPEED == 4 + // Very Low speed + #define SERIAL_DELAY 50 // micro sec + #define READ_WRITE_START_ADJUST 25 // cycles + #define READ_WRITE_WIDTH_ADJUST 10 // cycles +#else +#error Illegal Serial Speed +#endif + + +#define SERIAL_DELAY_HALF1 (SERIAL_DELAY/2) +#define SERIAL_DELAY_HALF2 (SERIAL_DELAY - SERIAL_DELAY/2) + +#define SLAVE_INT_WIDTH 1 +#define SLAVE_INT_RESPONSE_TIME SERIAL_DELAY + +uint8_t volatile serial_slave_buffer[SERIAL_SLAVE_BUFFER_LENGTH] = {0}; +uint8_t volatile serial_master_buffer[SERIAL_MASTER_BUFFER_LENGTH] = {0}; + +#define SLAVE_DATA_CORRUPT (1<<0) +volatile uint8_t status = 0; + +inline static +void serial_delay(void) { + _delay_us(SERIAL_DELAY); +} + +inline static +void serial_delay_half1(void) { + _delay_us(SERIAL_DELAY_HALF1); +} + +inline static +void serial_delay_half2(void) { + _delay_us(SERIAL_DELAY_HALF2); +} + +inline static +void serial_output(void) { + SERIAL_PIN_DDR |= SERIAL_PIN_MASK; +} + +// make the serial pin an input with pull-up resistor +inline static +void serial_input_with_pullup(void) { + SERIAL_PIN_DDR &= ~SERIAL_PIN_MASK; + SERIAL_PIN_PORT |= SERIAL_PIN_MASK; +} + +inline static +uint8_t serial_read_pin(void) { + return !!(SERIAL_PIN_INPUT & SERIAL_PIN_MASK); +} + +inline static +void serial_low(void) { + SERIAL_PIN_PORT &= ~SERIAL_PIN_MASK; +} + +inline static +void serial_high(void) { + SERIAL_PIN_PORT |= SERIAL_PIN_MASK; +} + +void serial_master_init(void) { + serial_output(); + serial_high(); +} + +void serial_slave_init(void) { + serial_input_with_pullup(); + +#if SERIAL_PIN_MASK == _BV(PD0) + // Enable INT0 + EIMSK |= _BV(INT0); + // Trigger on falling edge of INT0 + EICRA &= ~(_BV(ISC00) | _BV(ISC01)); +#elif SERIAL_PIN_MASK == _BV(PD2) + // Enable INT2 + EIMSK |= _BV(INT2); + // Trigger on falling edge of INT2 + EICRA &= ~(_BV(ISC20) | _BV(ISC21)); +#else + #error unknown SERIAL_PIN_MASK value +#endif +} + +// Used by the sender to synchronize timing with the reciver. +static +void sync_recv(void) { + for (int i = 0; i < SERIAL_DELAY*5 && serial_read_pin(); i++ ) { + } + // This shouldn't hang if the slave disconnects because the + // serial line will float to high if the slave does disconnect. + while (!serial_read_pin()); +} + +// Used by the reciver to send a synchronization signal to the sender. +static +void sync_send(void) { + serial_low(); + serial_delay(); + serial_high(); +} + +// Reads a byte from the serial line +static +uint8_t serial_read_byte(void) { + uint8_t byte = 0; + _delay_sub_us(READ_WRITE_START_ADJUST); + for ( uint8_t i = 0; i < 8; ++i) { + serial_delay_half1(); // read the middle of pulses + byte = (byte << 1) | serial_read_pin(); + _delay_sub_us(READ_WRITE_WIDTH_ADJUST); + serial_delay_half2(); + } + return byte; +} + +// Sends a byte with MSB ordering +static +void serial_write_byte(uint8_t data) { + uint8_t b = 1<<7; + while( b ) { + if(data & b) { + serial_high(); + } else { + serial_low(); + } + b >>= 1; + serial_delay(); + } + serial_low(); // sync_send() / senc_recv() need raise edge +} + +// interrupt handle to be used by the slave device +ISR(SERIAL_PIN_INTERRUPT) { + serial_output(); + + // slave send phase + uint8_t checksum = 0; + for (int i = 0; i < SERIAL_SLAVE_BUFFER_LENGTH; ++i) { + sync_send(); + serial_write_byte(serial_slave_buffer[i]); + checksum += serial_slave_buffer[i]; + } + sync_send(); + serial_write_byte(checksum); + + // slave switch to input + sync_send(); //0 + serial_delay_half1(); //1 + serial_low(); //2 + serial_input_with_pullup(); //2 + serial_delay_half1(); //3 + + // slave recive phase + uint8_t checksum_computed = 0; + for (int i = 0; i < SERIAL_MASTER_BUFFER_LENGTH; ++i) { + sync_recv(); + serial_master_buffer[i] = serial_read_byte(); + checksum_computed += serial_master_buffer[i]; + } + sync_recv(); + uint8_t checksum_received = serial_read_byte(); + + if ( checksum_computed != checksum_received ) { + status |= SLAVE_DATA_CORRUPT; + } else { + status &= ~SLAVE_DATA_CORRUPT; + } + + sync_recv(); //weit master output to high +} + +inline +bool serial_slave_DATA_CORRUPT(void) { + return status & SLAVE_DATA_CORRUPT; +} + +// Copies the serial_slave_buffer to the master and sends the +// serial_master_buffer to the slave. +// +// Returns: +// 0 => no error +// 1 => slave did not respond +// 2 => checksum error +int serial_update_buffers(void) { + // this code is very time dependent, so we need to disable interrupts + cli(); + + // signal to the slave that we want to start a transaction + serial_output(); + serial_low(); + _delay_us(SLAVE_INT_WIDTH); + + // wait for the slaves response + serial_input_with_pullup(); + _delay_us(SLAVE_INT_RESPONSE_TIME); + + // check if the slave is present + if (serial_read_pin()) { + // slave failed to pull the line low, assume not present + serial_output(); + serial_high(); + sei(); + return 1; + } + + // master recive phase + // if the slave is present syncronize with it + + uint8_t checksum_computed = 0; + // receive data from the slave + for (int i = 0; i < SERIAL_SLAVE_BUFFER_LENGTH; ++i) { + sync_recv(); + serial_slave_buffer[i] = serial_read_byte(); + checksum_computed += serial_slave_buffer[i]; + } + sync_recv(); + uint8_t checksum_received = serial_read_byte(); + + if (checksum_computed != checksum_received) { + serial_output(); + serial_high(); + sei(); + return 2; + } + + // master switch to output + sync_recv(); //0 + serial_delay(); //1 + serial_low(); //3 + serial_output(); // 3 + serial_delay_half1(); //4 + + // master send phase + uint8_t checksum = 0; + + for (int i = 0; i < SERIAL_MASTER_BUFFER_LENGTH; ++i) { + sync_send(); + serial_write_byte(serial_master_buffer[i]); + checksum += serial_master_buffer[i]; + } + sync_send(); + serial_write_byte(checksum); + + // always, release the line when not in use + sync_send(); + + sei(); + return 0; +} + +#endif |