qmk-firmware/drivers/avr/serial.c

/*
 * WARNING: be careful changing this code, it is very timing dependent
 *
 * 2018-10-28 checked
 *  avr-gcc 4.9.2
 *  avr-gcc 5.4.0
 *  avr-gcc 7.3.0
 */

#ifndef F_CPU
#    define F_CPU 16000000
#endif

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <stddef.h>
#include <stdbool.h>
#include "serial.h"

#ifdef SOFT_SERIAL_PIN

#    ifdef __AVR_ATmega32U4__
// if using ATmega32U4 I2C, can not use PD0 and PD1 in soft serial.
#        ifdef USE_AVR_I2C
#            if SOFT_SERIAL_PIN == D0 || SOFT_SERIAL_PIN == D1
#                error Using ATmega32U4 I2C, so can not use PD0, PD1
#            endif
#        endif

#        define setPinInputHigh(pin) (DDRx_ADDRESS(pin) &= ~_BV((pin)&0xF), PORTx_ADDRESS(pin) |= _BV((pin)&0xF))
#        define setPinOutput(pin) (DDRx_ADDRESS(pin) |= _BV((pin)&0xF))
#        define writePinHigh(pin) (PORTx_ADDRESS(pin) |= _BV((pin)&0xF))
#        define writePinLow(pin) (PORTx_ADDRESS(pin) &= ~_BV((pin)&0xF))
#        define readPin(pin) ((bool)(PINx_ADDRESS(pin) & _BV((pin)&0xF)))

#        if SOFT_SERIAL_PIN >= D0 && SOFT_SERIAL_PIN <= D3
#            if SOFT_SERIAL_PIN == D0
#                define EIMSK_BIT _BV(INT0)
#                define EICRx_BIT (~(_BV(ISC00) | _BV(ISC01)))
#                define SERIAL_PIN_INTERRUPT INT0_vect
#            elif SOFT_SERIAL_PIN == D1
#                define EIMSK_BIT _BV(INT1)
#                define EICRx_BIT (~(_BV(ISC10) | _BV(ISC11)))
#                define SERIAL_PIN_INTERRUPT INT1_vect
#            elif SOFT_SERIAL_PIN == D2
#                define EIMSK_BIT _BV(INT2)
#                define EICRx_BIT (~(_BV(ISC20) | _BV(ISC21)))
#                define SERIAL_PIN_INTERRUPT INT2_vect
#            elif SOFT_SERIAL_PIN == D3
#                define EIMSK_BIT _BV(INT3)
#                define EICRx_BIT (~(_BV(ISC30) | _BV(ISC31)))
#                define SERIAL_PIN_INTERRUPT INT3_vect
#            endif
#        elif SOFT_SERIAL_PIN == E6
#            define EIMSK_BIT _BV(INT6)
#            define EICRx_BIT (~(_BV(ISC60) | _BV(ISC61)))
#            define SERIAL_PIN_INTERRUPT INT6_vect
#        else
#            error invalid SOFT_SERIAL_PIN value
#        endif

#    else
#        error serial.c now support ATmega32U4 only
#    endif

#    define ALWAYS_INLINE __attribute__((always_inline))
#    define NO_INLINE __attribute__((noinline))
#    define _delay_sub_us(x) __builtin_avr_delay_cycles(x)

// parity check
#    define ODD_PARITY 1
#    define EVEN_PARITY 0
#    define PARITY EVEN_PARITY

#    ifdef SERIAL_DELAY
// custom setup in config.h
// #define TID_SEND_ADJUST 2
// #define SERIAL_DELAY 6             // micro sec
// #define READ_WRITE_START_ADJUST 30 // cycles
// #define READ_WRITE_WIDTH_ADJUST 8 // cycles
#    else
// ============ Standard setups ============

#        ifndef SELECT_SOFT_SERIAL_SPEED
#            define SELECT_SOFT_SERIAL_SPEED 1
//  0: about 189kbps (Experimental only)
//  1: about 137kbps (default)
//  2: about 75kbps
//  3: about 39kbps
//  4: about 26kbps
//  5: about 20kbps
#        endif

#        if __GNUC__ < 6
#            define TID_SEND_ADJUST 14
#        else
#            define TID_SEND_ADJUST 2
#        endif

#        if SELECT_SOFT_SERIAL_SPEED == 0
// Very High speed
#            define SERIAL_DELAY 4  // micro sec
#            if __GNUC__ < 6
#                define READ_WRITE_START_ADJUST 33  // cycles
#                define READ_WRITE_WIDTH_ADJUST 3   // cycles
#            else
#                define READ_WRITE_START_ADJUST 34  // cycles
#                define READ_WRITE_WIDTH_ADJUST 7   // cycles
#            endif
#        elif SELECT_SOFT_SERIAL_SPEED == 1
// High speed
#            define SERIAL_DELAY 6  // micro sec
#            if __GNUC__ < 6
#                define READ_WRITE_START_ADJUST 30  // cycles
#                define READ_WRITE_WIDTH_ADJUST 3   // cycles
#            else
#                define READ_WRITE_START_ADJUST 33  // cycles
#                define READ_WRITE_WIDTH_ADJUST 7   // cycles
#            endif
#        elif SELECT_SOFT_SERIAL_SPEED == 2
// Middle speed
#            define SERIAL_DELAY 12             // micro sec
#            define READ_WRITE_START_ADJUST 30  // cycles
#            if __GNUC__ < 6
#                define READ_WRITE_WIDTH_ADJUST 3  // cycles
#            else
#                define READ_WRITE_WIDTH_ADJUST 7  // cycles
#            endif
#        elif SELECT_SOFT_SERIAL_SPEED == 3
// Low speed
#            define SERIAL_DELAY 24             // micro sec
#            define READ_WRITE_START_ADJUST 30  // cycles
#            if __GNUC__ < 6
#                define READ_WRITE_WIDTH_ADJUST 3  // cycles
#            else
#                define READ_WRITE_WIDTH_ADJUST 7  // cycles
#            endif
#        elif SELECT_SOFT_SERIAL_SPEED == 4
// Very Low speed
#            define SERIAL_DELAY 36             // micro sec
#            define READ_WRITE_START_ADJUST 30  // cycles
#            if __GNUC__ < 6
#                define READ_WRITE_WIDTH_ADJUST 3  // cycles
#            else
#                define READ_WRITE_WIDTH_ADJUST 7  // cycles
#            endif
#        elif SELECT_SOFT_SERIAL_SPEED == 5
// Ultra Low speed
#            define SERIAL_DELAY 48             // micro sec
#            define READ_WRITE_START_ADJUST 30  // cycles
#            if __GNUC__ < 6
#                define READ_WRITE_WIDTH_ADJUST 3  // cycles
#            else
#                define READ_WRITE_WIDTH_ADJUST 7  // cycles
#            endif
#        else
#            error invalid SELECT_SOFT_SERIAL_SPEED value
#        endif /* SELECT_SOFT_SERIAL_SPEED */
#    endif     /* SERIAL_DELAY */

#    define SERIAL_DELAY_HALF1 (SERIAL_DELAY / 2)
#    define SERIAL_DELAY_HALF2 (SERIAL_DELAY - SERIAL_DELAY / 2)

#    define SLAVE_INT_WIDTH_US 1
#    ifndef SERIAL_USE_MULTI_TRANSACTION
#        define SLAVE_INT_RESPONSE_TIME SERIAL_DELAY
#    else
#        define SLAVE_INT_ACK_WIDTH_UNIT 2
#        define SLAVE_INT_ACK_WIDTH 4
#    endif

static SSTD_t *Transaction_table      = NULL;
static uint8_t Transaction_table_size = 0;

inline static void serial_delay(void) ALWAYS_INLINE;
inline static void serial_delay(void) { _delay_us(SERIAL_DELAY); }

inline static void serial_delay_half1(void) ALWAYS_INLINE;
inline static void serial_delay_half1(void) { _delay_us(SERIAL_DELAY_HALF1); }

inline static void serial_delay_half2(void) ALWAYS_INLINE;
inline static void serial_delay_half2(void) { _delay_us(SERIAL_DELAY_HALF2); }

inline static void serial_output(void) ALWAYS_INLINE;
inline static void serial_output(void) { setPinOutput(SOFT_SERIAL_PIN); }

// make the serial pin an input with pull-up resistor
inline static void serial_input_with_pullup(void) ALWAYS_INLINE;
inline static void serial_input_with_pullup(void) { setPinInputHigh(SOFT_SERIAL_PIN); }

inline static uint8_t serial_read_pin(void) ALWAYS_INLINE;
inline static uint8_t serial_read_pin(void) { return !!readPin(SOFT_SERIAL_PIN); }

inline static void serial_low(void) ALWAYS_INLINE;
inline static void serial_low(void) { writePinLow(SOFT_SERIAL_PIN); }

inline static void serial_high(void) ALWAYS_INLINE;
inline static void serial_high(void) { writePinHigh(SOFT_SERIAL_PIN); }

void soft_serial_initiator_init(SSTD_t *sstd_table, int sstd_table_size) {
    Transaction_table      = sstd_table;
    Transaction_table_size = (uint8_t)sstd_table_size;
    serial_output();
    serial_high();
}

void soft_serial_target_init(SSTD_t *sstd_table, int sstd_table_size) {
    Transaction_table      = sstd_table;
    Transaction_table_size = (uint8_t)sstd_table_size;
    serial_input_with_pullup();

    // Enable INT0-INT3,INT6
    EIMSK |= EIMSK_BIT;
#    if SOFT_SERIAL_PIN == E6
    // Trigger on falling edge of INT6
    EICRB &= EICRx_BIT;
#    else
    // Trigger on falling edge of INT0-INT3
    EICRA &= EICRx_BIT;
#    endif
}

// Used by the sender to synchronize timing with the reciver.
static void sync_recv(void) NO_INLINE;
static void sync_recv(void) {
    for (uint8_t i = 0; i < SERIAL_DELAY * 5 && serial_read_pin(); i++) {
    }
    // This shouldn't hang if the target disconnects because the
    // serial line will float to high if the target does disconnect.
    while (!serial_read_pin())
        ;
}

// Used by the reciver to send a synchronization signal to the sender.
static void sync_send(void) NO_INLINE;
static void sync_send(void) {
    serial_low();
    serial_delay();
    serial_high();
}

// Reads a byte from the serial line
static uint8_t serial_read_chunk(uint8_t *pterrcount, uint8_t bit) NO_INLINE;
static uint8_t serial_read_chunk(uint8_t *pterrcount, uint8_t bit) {
    uint8_t byte, i, p, pb;

    _delay_sub_us(READ_WRITE_START_ADJUST);
    for (i = 0, byte = 0, p = PARITY; i < bit; i++) {
        serial_delay_half1();  // read the middle of pulses
        if (serial_read_pin()) {
            byte = (byte << 1) | 1;
            p ^= 1;
        } else {
            byte = (byte << 1) | 0;
            p ^= 0;
        }
        _delay_sub_us(READ_WRITE_WIDTH_ADJUST);
        serial_delay_half2();
    }
    /* recive parity bit */
    serial_delay_half1();  // read the middle of pulses
    pb = serial_read_pin();
    _delay_sub_us(READ_WRITE_WIDTH_ADJUST);
    serial_delay_half2();

    *pterrcount += (p != pb) ? 1 : 0;

    return byte;
}

// Sends a byte with MSB ordering
void serial_write_chunk(uint8_t data, uint8_t bit) NO_INLINE;
void serial_write_chunk(uint8_t data, uint8_t bit) {
    uint8_t b, p;
    for (p = PARITY, b = 1 << (bit - 1); b; b >>= 1) {
        if (data & b) {
            serial_high();
            p ^= 1;
        } else {
            serial_low();
            p ^= 0;
        }
        serial_delay();
    }
    /* send parity bit */
    if (p & 1) {
        serial_high();
    } else {
        serial_low();
    }
    serial_delay();

    serial_low();  // sync_send() / senc_recv() need raise edge
}

static void serial_send_packet(uint8_t *buffer, uint8_t size) NO_INLINE;
static void serial_send_packet(uint8_t *buffer, uint8_t size) {
    for (uint8_t i = 0; i < size; ++i) {
        uint8_t data;
        data = buffer[i];
        sync_send();
        serial_write_chunk(data, 8);
    }
}

static uint8_t serial_recive_packet(uint8_t *buffer, uint8_t size) NO_INLINE;
static uint8_t serial_recive_packet(uint8_t *buffer, uint8_t size) {
    uint8_t pecount = 0;
    for (uint8_t i = 0; i < size; ++i) {
        uint8_t data;
        sync_recv();
        data      = serial_read_chunk(&pecount, 8);
        buffer[i] = data;
    }
    return pecount == 0;
}

inline static void change_sender2reciver(void) {
    sync_send();                 // 0
    serial_delay_half1();        // 1
    serial_low();                // 2
    serial_input_with_pullup();  // 2
    serial_delay_half1();        // 3
}

inline static void change_reciver2sender(void) {
    sync_recv();           // 0
    serial_delay();        // 1
    serial_low();          // 3
    serial_output();       // 3
    serial_delay_half1();  // 4
}

static inline uint8_t nibble_bits_count(uint8_t bits) {
    bits = (bits & 0x5) + (bits >> 1 & 0x5);
    bits = (bits & 0x3) + (bits >> 2 & 0x3);
    return bits;
}

// interrupt handle to be used by the target device
ISR(SERIAL_PIN_INTERRUPT) {
#    ifndef SERIAL_USE_MULTI_TRANSACTION
    serial_low();
    serial_output();
    SSTD_t *trans = Transaction_table;
#    else
    // recive transaction table index
    uint8_t tid, bits;
    uint8_t pecount = 0;
    sync_recv();
    bits = serial_read_chunk(&pecount, 7);
    tid  = bits >> 3;
    bits = (bits & 7) != nibble_bits_count(tid);
    if (bits || pecount > 0 || tid > Transaction_table_size) {
        return;
    }
    serial_delay_half1();

    serial_high();  // response step1 low->high
    serial_output();
    _delay_sub_us(SLAVE_INT_ACK_WIDTH_UNIT * SLAVE_INT_ACK_WIDTH);
    SSTD_t *trans = &Transaction_table[tid];
    serial_low();  // response step2 ack high->low
#    endif

    // target send phase
    if (trans->target2initiator_buffer_size > 0) serial_send_packet((uint8_t *)trans->target2initiator_buffer, trans->target2initiator_buffer_size);
    // target switch to input
    change_sender2reciver();

    // target recive phase
    if (trans->initiator2target_buffer_size > 0) {
        if (serial_recive_packet((uint8_t *)trans->initiator2target_buffer, trans->initiator2target_buffer_size)) {
            *trans->status = TRANSACTION_ACCEPTED;
        } else {
            *trans->status = TRANSACTION_DATA_ERROR;
        }
    } else {
        *trans->status = TRANSACTION_ACCEPTED;
    }

    sync_recv();  // weit initiator output to high
}

/////////
//  start transaction by initiator
//
// int  soft_serial_transaction(int sstd_index)
//
// Returns:
//    TRANSACTION_END
//    TRANSACTION_NO_RESPONSE
//    TRANSACTION_DATA_ERROR
// this code is very time dependent, so we need to disable interrupts
#    ifndef SERIAL_USE_MULTI_TRANSACTION
int soft_serial_transaction(void) {
    SSTD_t *trans = Transaction_table;
#    else
int soft_serial_transaction(int sstd_index) {
    if (sstd_index > Transaction_table_size) return TRANSACTION_TYPE_ERROR;
    SSTD_t *trans = &Transaction_table[sstd_index];
#    endif
    cli();

    // signal to the target that we want to start a transaction
    serial_output();
    serial_low();
    _delay_us(SLAVE_INT_WIDTH_US);

#    ifndef SERIAL_USE_MULTI_TRANSACTION
    // wait for the target response
    serial_input_with_pullup();
    _delay_us(SLAVE_INT_RESPONSE_TIME);

    // check if the target is present
    if (serial_read_pin()) {
        // target failed to pull the line low, assume not present
        serial_output();
        serial_high();
        *trans->status = TRANSACTION_NO_RESPONSE;
        sei();
        return TRANSACTION_NO_RESPONSE;
    }

#    else
    // send transaction table index
    int tid = (sstd_index << 3) | (7 & nibble_bits_count(sstd_index));
    sync_send();
    _delay_sub_us(TID_SEND_ADJUST);
    serial_write_chunk(tid, 7);
    serial_delay_half1();

    // wait for the target response (step1 low->high)
    serial_input_with_pullup();
    while (!serial_read_pin()) {
        _delay_sub_us(2);
    }

    // check if the target is present (step2 high->low)
    for (int i = 0; serial_read_pin(); i++) {
        if (i > SLAVE_INT_ACK_WIDTH + 1) {
            // slave failed to pull the line low, assume not present
            serial_output();
            serial_high();
            *trans->status = TRANSACTION_NO_RESPONSE;
            sei();
            return TRANSACTION_NO_RESPONSE;
        }
        _delay_sub_us(SLAVE_INT_ACK_WIDTH_UNIT);
    }
#    endif

    // initiator recive phase
    // if the target is present syncronize with it
    if (trans->target2initiator_buffer_size > 0) {
        if (!serial_recive_packet((uint8_t *)trans->target2initiator_buffer, trans->target2initiator_buffer_size)) {
            serial_output();
            serial_high();
            *trans->status = TRANSACTION_DATA_ERROR;
            sei();
            return TRANSACTION_DATA_ERROR;
        }
    }

    // initiator switch to output
    change_reciver2sender();

    // initiator send phase
    if (trans->initiator2target_buffer_size > 0) {
        serial_send_packet((uint8_t *)trans->initiator2target_buffer, trans->initiator2target_buffer_size);
    }

    // always, release the line when not in use
    sync_send();

    *trans->status = TRANSACTION_END;
    sei();
    return TRANSACTION_END;
}

#    ifdef SERIAL_USE_MULTI_TRANSACTION
int soft_serial_get_and_clean_status(int sstd_index) {
    SSTD_t *trans = &Transaction_table[sstd_index];
    cli();
    int retval     = *trans->status;
    *trans->status = 0;
    ;
    sei();
    return retval;
}
#    endif

#endif

// Helix serial.c history
//   2018-1-29 fork from let's split and add PD2, modify sync_recv() (#2308, bceffdefc)
//   2018-6-28 bug fix master to slave comm and speed up (#3255, 1038bbef4)
//             (adjusted with avr-gcc 4.9.2)
//   2018-7-13 remove USE_SERIAL_PD2 macro (#3374, f30d6dd78)
//             (adjusted with avr-gcc 4.9.2)
//   2018-8-11 add support multi-type transaction (#3608, feb5e4aae)
//             (adjusted with avr-gcc 4.9.2)
//   2018-10-21 fix serial and RGB animation conflict (#4191, 4665e4fff)
//             (adjusted with avr-gcc 7.3.0)
//   2018-10-28 re-adjust compiler depend value of delay (#4269, 8517f8a66)
//             (adjusted with avr-gcc 5.4.0, 7.3.0)
//   2018-12-17 copy to TOP/quantum/split_common/ and remove backward compatibility code (#4669)