unleashed-firmware/lib/one_wire/one_wire_slave.c

#include "one_wire_slave.h"

#include <furi.h>
#include <furi_hal.h>

#define TH_TIMEOUT_MAX 15000 /* Maximum time before general timeout */

typedef enum {
    OneWireSlaveErrorNone = 0,
    OneWireSlaveErrorResetInProgress,
    OneWireSlaveErrorPresenceConflict,
    OneWireSlaveErrorInvalidCommand,
    OneWireSlaveErrorTimeout,
} OneWireSlaveError;

typedef struct {
    uint16_t trstl_min; /* Minimum Reset Low time */
    uint16_t trstl_max; /* Maximum Reset Low time */

    uint16_t tpdh_typ; /* Typical Presence Detect High time */
    uint16_t tpdl_min; /* Minimum Presence Detect Low time */
    uint16_t tpdl_max; /* Maximum Presence Detect Low time */

    uint16_t tslot_min; /* Minimum Read/Write Slot time */
    uint16_t tslot_max; /* Maximum Read/Write Slot time */

    uint16_t tw1l_max; /* Maximum Master Write 1 time */
    uint16_t trl_tmsr_max; /* Maximum Master Read Low + Read Sample time */
} OneWireSlaveTimings;

struct OneWireSlave {
    const GpioPin* gpio_pin;
    const OneWireSlaveTimings* timings;
    OneWireSlaveError error;

    bool is_first_reset;
    bool is_short_reset;

    OneWireSlaveResetCallback reset_callback;
    OneWireSlaveCommandCallback command_callback;
    OneWireSlaveResultCallback result_callback;

    void* reset_callback_context;
    void* result_callback_context;
    void* command_callback_context;
};

static const OneWireSlaveTimings onewire_slave_timings_normal = {
    .trstl_min = 270,
    .trstl_max = 1200,

    .tpdh_typ = 20,
    .tpdl_min = 100,
    .tpdl_max = 480,

    .tslot_min = 60,
    .tslot_max = 135,

    .tw1l_max = 20,
    .trl_tmsr_max = 30,
};

static const OneWireSlaveTimings onewire_slave_timings_overdrive = {
    .trstl_min = 48,
    .trstl_max = 80,

    .tpdh_typ = 0,
    .tpdl_min = 8,
    .tpdl_max = 24,

    .tslot_min = 6,
    .tslot_max = 16,

    .tw1l_max = 2,
    .trl_tmsr_max = 3,
};

/*********************** PRIVATE ***********************/

static bool
    onewire_slave_wait_while_gpio_is(OneWireSlave* bus, uint32_t time_us, const bool pin_value) {
    const uint32_t time_start = DWT->CYCCNT;
    const uint32_t time_ticks = time_us * furi_hal_cortex_instructions_per_microsecond();

    uint32_t time_elapsed;

    do { //-V1044
        time_elapsed = DWT->CYCCNT - time_start;
        if(furi_hal_gpio_read(bus->gpio_pin) != pin_value) {
            return time_ticks >= time_elapsed;
        }
    } while(time_elapsed < time_ticks);

    return false;
}

static inline bool onewire_slave_show_presence(OneWireSlave* bus) {
    const OneWireSlaveTimings* timings = bus->timings;
    // wait until the bus is high (might return immediately)
    onewire_slave_wait_while_gpio_is(bus, timings->trstl_max, false);
    // wait while master delay presence check
    furi_delay_us(timings->tpdh_typ);

    // show presence
    furi_hal_gpio_write(bus->gpio_pin, false);
    furi_delay_us(timings->tpdl_min);
    furi_hal_gpio_write(bus->gpio_pin, true);

    // somebody also can show presence
    const uint32_t wait_low_time = timings->tpdl_max - timings->tpdl_min;

    // so we will wait
    if(!onewire_slave_wait_while_gpio_is(bus, wait_low_time, false)) {
        bus->error = OneWireSlaveErrorPresenceConflict;
        return false;
    }

    return true;
}

static inline bool onewire_slave_receive_and_process_command(OneWireSlave* bus) {
    /* Reset condition detected, send a presence pulse and reset protocol state */
    if(bus->error == OneWireSlaveErrorResetInProgress) {
        if(!bus->is_first_reset) {
            /* Guess the reset type */
            bus->is_short_reset = onewire_slave_wait_while_gpio_is(
                bus,
                onewire_slave_timings_overdrive.trstl_max -
                    onewire_slave_timings_overdrive.tslot_max,
                false);
        } else {
            bus->is_first_reset = false;
        }

        furi_assert(bus->reset_callback);

        if(bus->reset_callback(bus->is_short_reset, bus->reset_callback_context)) {
            if(onewire_slave_show_presence(bus)) {
                bus->error = OneWireSlaveErrorNone;
                return true;
            }
        }

    } else if(bus->error == OneWireSlaveErrorNone) {
        uint8_t command;
        if(onewire_slave_receive(bus, &command, sizeof(command))) {
            furi_assert(bus->command_callback);
            if(bus->command_callback(command, bus->command_callback_context)) {
                return true;
            }
        }

        return (bus->error == OneWireSlaveErrorResetInProgress);
    }

    return false;
}

static inline bool onewire_slave_bus_start(OneWireSlave* bus) {
    FURI_CRITICAL_ENTER();
    furi_hal_gpio_init(bus->gpio_pin, GpioModeOutputOpenDrain, GpioPullNo, GpioSpeedLow);

    while(onewire_slave_receive_and_process_command(bus))
        ;

    const bool result = (bus->error == OneWireSlaveErrorNone);

    furi_hal_gpio_init(bus->gpio_pin, GpioModeInterruptRiseFall, GpioPullNo, GpioSpeedLow);
    FURI_CRITICAL_EXIT();

    return result;
}

static void onewire_slave_exti_callback(void* context) {
    OneWireSlave* bus = context;

    const volatile bool input_state = furi_hal_gpio_read(bus->gpio_pin);
    static uint32_t pulse_start = 0;

    if(input_state) {
        const uint32_t pulse_length =
            (DWT->CYCCNT - pulse_start) / furi_hal_cortex_instructions_per_microsecond();

        if((pulse_length >= onewire_slave_timings_overdrive.trstl_min) &&
           (pulse_length <= onewire_slave_timings_normal.trstl_max)) {
            /* Start in reset state in order to send a presence pulse immediately */
            bus->error = OneWireSlaveErrorResetInProgress;
            /* Determine reset type (chooses speed mode if supported by the emulated device) */
            bus->is_short_reset = pulse_length <= onewire_slave_timings_overdrive.trstl_max;
            /* Initial reset allows going directly into overdrive mode */
            bus->is_first_reset = true;

            const bool result = onewire_slave_bus_start(bus);

            if(result && bus->result_callback != NULL) {
                bus->result_callback(bus->result_callback_context);
            }
        }

    } else {
        pulse_start = DWT->CYCCNT;
    }
};

/*********************** PUBLIC ***********************/

OneWireSlave* onewire_slave_alloc(const GpioPin* gpio_pin) {
    OneWireSlave* bus = malloc(sizeof(OneWireSlave));

    bus->gpio_pin = gpio_pin;
    bus->timings = &onewire_slave_timings_normal;
    bus->error = OneWireSlaveErrorNone;

    return bus;
}

void onewire_slave_free(OneWireSlave* bus) {
    onewire_slave_stop(bus);
    free(bus);
}

void onewire_slave_start(OneWireSlave* bus) {
    furi_hal_gpio_add_int_callback(bus->gpio_pin, onewire_slave_exti_callback, bus);
    furi_hal_gpio_write(bus->gpio_pin, true);
    furi_hal_gpio_init(bus->gpio_pin, GpioModeInterruptRiseFall, GpioPullNo, GpioSpeedLow);
}

void onewire_slave_stop(OneWireSlave* bus) {
    furi_hal_gpio_write(bus->gpio_pin, true);
    furi_hal_gpio_init(bus->gpio_pin, GpioModeAnalog, GpioPullNo, GpioSpeedLow);
    furi_hal_gpio_remove_int_callback(bus->gpio_pin);
}

void onewire_slave_set_reset_callback(
    OneWireSlave* bus,
    OneWireSlaveResetCallback callback,
    void* context) {
    bus->reset_callback = callback;
    bus->reset_callback_context = context;
}

void onewire_slave_set_command_callback(
    OneWireSlave* bus,
    OneWireSlaveCommandCallback callback,
    void* context) {
    bus->command_callback = callback;
    bus->command_callback_context = context;
}

void onewire_slave_set_result_callback(
    OneWireSlave* bus,
    OneWireSlaveResultCallback result_cb,
    void* context) {
    bus->result_callback = result_cb;
    bus->result_callback_context = context;
}

bool onewire_slave_receive_bit(OneWireSlave* bus) {
    const OneWireSlaveTimings* timings = bus->timings;
    // wait while bus is low
    if(!onewire_slave_wait_while_gpio_is(bus, timings->tslot_max, false)) {
        bus->error = OneWireSlaveErrorResetInProgress;
        return false;
    }

    // wait while bus is high
    if(!onewire_slave_wait_while_gpio_is(bus, TH_TIMEOUT_MAX, true)) {
        bus->error = OneWireSlaveErrorTimeout;
        return false;
    }

    // wait a time of zero
    return onewire_slave_wait_while_gpio_is(bus, timings->tw1l_max, false);
}

bool onewire_slave_send_bit(OneWireSlave* bus, bool value) {
    const OneWireSlaveTimings* timings = bus->timings;
    // wait while bus is low
    if(!onewire_slave_wait_while_gpio_is(bus, timings->tslot_max, false)) {
        bus->error = OneWireSlaveErrorResetInProgress;
        return false;
    }

    // wait while bus is high
    if(!onewire_slave_wait_while_gpio_is(bus, TH_TIMEOUT_MAX, true)) {
        bus->error = OneWireSlaveErrorTimeout;
        return false;
    }

    // choose write time
    uint32_t time;

    if(!value) {
        furi_hal_gpio_write(bus->gpio_pin, false);
        time = timings->trl_tmsr_max;
    } else {
        time = timings->tslot_min;
    }

    // hold line for ZERO or ONE time
    furi_delay_us(time);
    furi_hal_gpio_write(bus->gpio_pin, true);

    return true;
}

bool onewire_slave_send(OneWireSlave* bus, const uint8_t* data, size_t data_size) {
    furi_hal_gpio_write(bus->gpio_pin, true);

    size_t bytes_sent = 0;

    // bytes loop
    for(; bytes_sent < data_size; ++bytes_sent) {
        const uint8_t data_byte = data[bytes_sent];

        // bit loop
        for(uint8_t bit_mask = 0x01; bit_mask != 0; bit_mask <<= 1) {
            if(!onewire_slave_send_bit(bus, bit_mask & data_byte)) {
                return false;
            }
        }
    }
    return true;
}

bool onewire_slave_receive(OneWireSlave* bus, uint8_t* data, size_t data_size) {
    furi_hal_gpio_write(bus->gpio_pin, true);

    size_t bytes_received = 0;

    for(; bytes_received < data_size; ++bytes_received) {
        uint8_t value = 0;

        for(uint8_t bit_mask = 0x01; bit_mask != 0; bit_mask <<= 1) {
            if(onewire_slave_receive_bit(bus)) {
                value |= bit_mask;
            }

            if(bus->error != OneWireSlaveErrorNone) {
                return false;
            }
        }

        data[bytes_received] = value;
    }
    return true;
}

void onewire_slave_set_overdrive(OneWireSlave* bus, bool set) {
    const OneWireSlaveTimings* new_timings = set ? &onewire_slave_timings_overdrive :
                                                   &onewire_slave_timings_normal;
    if(bus->timings != new_timings) {
        /* Prevent erroneous reset by waiting for the previous time slot to finish */
        onewire_slave_wait_while_gpio_is(bus, bus->timings->tslot_max, false);
        bus->timings = new_timings;
    }
}