circuitpython/extmod/modonewire.c

// SPDX-FileCopyrightText: 2014 MicroPython & CircuitPython contributors (https://github.com/adafruit/circuitpython/graphs/contributors)
// SPDX-FileCopyrightText: Copyright (c) 2015-2017 Damien P. George
//
// SPDX-License-Identifier: MIT

#include <stdio.h>
#include <stdint.h>

#include "py/obj.h"
#include "py/mphal.h"

/******************************************************************************/
// Low-level 1-Wire routines

#define TIMING_RESET1 (480)
#define TIMING_RESET2 (40)
#define TIMING_RESET3 (420)
#define TIMING_READ1 (5)
#define TIMING_READ2 (5)
#define TIMING_READ3 (40)
#define TIMING_WRITE1 (10)
#define TIMING_WRITE2 (50)
#define TIMING_WRITE3 (10)

STATIC int onewire_bus_reset(mp_hal_pin_obj_t pin) {
    mp_hal_pin_write(pin, 0);
    mp_hal_delay_us(TIMING_RESET1);
    uint32_t i = mp_hal_quiet_timing_enter();
    mp_hal_pin_write(pin, 1);
    mp_hal_delay_us_fast(TIMING_RESET2);
    int status = !mp_hal_pin_read(pin);
    mp_hal_quiet_timing_exit(i);
    mp_hal_delay_us(TIMING_RESET3);
    return status;
}

STATIC int onewire_bus_readbit(mp_hal_pin_obj_t pin) {
    mp_hal_pin_write(pin, 1);
    uint32_t i = mp_hal_quiet_timing_enter();
    mp_hal_pin_write(pin, 0);
    mp_hal_delay_us_fast(TIMING_READ1);
    mp_hal_pin_write(pin, 1);
    mp_hal_delay_us_fast(TIMING_READ2);
    int value = mp_hal_pin_read(pin);
    mp_hal_quiet_timing_exit(i);
    mp_hal_delay_us_fast(TIMING_READ3);
    return value;
}

STATIC void onewire_bus_writebit(mp_hal_pin_obj_t pin, int value) {
    uint32_t i = mp_hal_quiet_timing_enter();
    mp_hal_pin_write(pin, 0);
    mp_hal_delay_us_fast(TIMING_WRITE1);
    if (value) {
        mp_hal_pin_write(pin, 1);
    }
    mp_hal_delay_us_fast(TIMING_WRITE2);
    mp_hal_pin_write(pin, 1);
    mp_hal_delay_us_fast(TIMING_WRITE3);
    mp_hal_quiet_timing_exit(i);
}

/******************************************************************************/
// MicroPython bindings

STATIC mp_obj_t onewire_reset(mp_obj_t pin_in) {
    return mp_obj_new_bool(onewire_bus_reset(mp_hal_get_pin_obj(pin_in)));
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(onewire_reset_obj, onewire_reset);

STATIC mp_obj_t onewire_readbit(mp_obj_t pin_in) {
    return MP_OBJ_NEW_SMALL_INT(onewire_bus_readbit(mp_hal_get_pin_obj(pin_in)));
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(onewire_readbit_obj, onewire_readbit);

STATIC mp_obj_t onewire_readbyte(mp_obj_t pin_in) {
    mp_hal_pin_obj_t pin = mp_hal_get_pin_obj(pin_in);
    uint8_t value = 0;
    for (int i = 0; i < 8; ++i) {
        value |= onewire_bus_readbit(pin) << i;
    }
    return MP_OBJ_NEW_SMALL_INT(value);
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(onewire_readbyte_obj, onewire_readbyte);

STATIC mp_obj_t onewire_writebit(mp_obj_t pin_in, mp_obj_t value_in) {
    onewire_bus_writebit(mp_hal_get_pin_obj(pin_in), mp_obj_get_int(value_in));
    return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_2(onewire_writebit_obj, onewire_writebit);

STATIC mp_obj_t onewire_writebyte(mp_obj_t pin_in, mp_obj_t value_in) {
    mp_hal_pin_obj_t pin = mp_hal_get_pin_obj(pin_in);
    int value = mp_obj_get_int(value_in);
    for (int i = 0; i < 8; ++i) {
        onewire_bus_writebit(pin, value & 1);
        value >>= 1;
    }
    return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_2(onewire_writebyte_obj, onewire_writebyte);

STATIC mp_obj_t onewire_crc8(mp_obj_t data) {
    mp_buffer_info_t bufinfo;
    mp_get_buffer_raise(data, &bufinfo, MP_BUFFER_READ);
    uint8_t crc = 0;
    for (size_t i = 0; i < bufinfo.len; ++i) {
        uint8_t byte = ((uint8_t *)bufinfo.buf)[i];
        for (int b = 0; b < 8; ++b) {
            uint8_t fb_bit = (crc ^ byte) & 0x01;
            if (fb_bit == 0x01) {
                crc = crc ^ 0x18;
            }
            crc = (crc >> 1) & 0x7f;
            if (fb_bit == 0x01) {
                crc = crc | 0x80;
            }
            byte = byte >> 1;
        }
    }
    return MP_OBJ_NEW_SMALL_INT(crc);
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(onewire_crc8_obj, onewire_crc8);

STATIC const mp_rom_map_elem_t onewire_module_globals_table[] = {
    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_onewire) },

    { MP_ROM_QSTR(MP_QSTR_reset), MP_ROM_PTR(&onewire_reset_obj) },
    { MP_ROM_QSTR(MP_QSTR_readbit), MP_ROM_PTR(&onewire_readbit_obj) },
    { MP_ROM_QSTR(MP_QSTR_readbyte), MP_ROM_PTR(&onewire_readbyte_obj) },
    { MP_ROM_QSTR(MP_QSTR_writebit), MP_ROM_PTR(&onewire_writebit_obj) },
    { MP_ROM_QSTR(MP_QSTR_writebyte), MP_ROM_PTR(&onewire_writebyte_obj) },
    { MP_ROM_QSTR(MP_QSTR_crc8), MP_ROM_PTR(&onewire_crc8_obj) },
};

STATIC MP_DEFINE_CONST_DICT(onewire_module_globals, onewire_module_globals_table);

const mp_obj_module_t mp_module_onewire = {
    .base = { &mp_type_module },
    .globals = (mp_obj_dict_t *)&onewire_module_globals,
};