esp-idf/examples/peripherals/rmt/onewire_ds18b20/main/ds18b20.c

/*
 * SPDX-FileCopyrightText: 2022 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Unlicense OR CC0-1.0
 */
#include <string.h>
#include "ds18b20.h"
#include "esp_check.h"

static const char *TAG = "ds18b20";

esp_err_t ds18b20_trigger_temperature_conversion(onewire_bus_handle_t handle, const uint8_t *rom_number)
{
    ESP_RETURN_ON_FALSE(handle, ESP_ERR_INVALID_ARG, TAG, "invalid 1-wire handle");

    ESP_RETURN_ON_ERROR(onewire_bus_reset(handle), TAG, "error while resetting bus"); // reset bus and check if the device is present

    uint8_t tx_buffer[10];
    uint8_t tx_buffer_size;

    if (rom_number) { // specify rom id
        tx_buffer[0] = ONEWIRE_CMD_MATCH_ROM;
        tx_buffer[9] = DS18B20_CMD_CONVERT_TEMP;
        memcpy(&tx_buffer[1], rom_number, 8);
        tx_buffer_size = 10;
    } else { // skip rom id
        tx_buffer[0] = ONEWIRE_CMD_SKIP_ROM;
        tx_buffer[1] = DS18B20_CMD_CONVERT_TEMP;
        tx_buffer_size = 2;
    }

    ESP_RETURN_ON_ERROR(onewire_bus_write_bytes(handle, tx_buffer, tx_buffer_size),
                        TAG, "error while triggering temperature convert");

    return ESP_OK;
}

esp_err_t ds18b20_get_temperature(onewire_bus_handle_t handle, const uint8_t *rom_number, float *temperature)
{
    ESP_RETURN_ON_FALSE(handle, ESP_ERR_INVALID_ARG, TAG, "invalid 1-wire handle");
    ESP_RETURN_ON_FALSE(temperature, ESP_ERR_INVALID_ARG, TAG, "invalid temperature pointer");

    ESP_RETURN_ON_ERROR(onewire_bus_reset(handle), TAG, "error while resetting bus"); // reset bus and check if the device is present

    ds18b20_scratchpad_t scratchpad;

    uint8_t tx_buffer[10];
    uint8_t tx_buffer_size;

    if (rom_number) { // specify rom id
        tx_buffer[0] = ONEWIRE_CMD_MATCH_ROM;
        tx_buffer[9] = DS18B20_CMD_READ_SCRATCHPAD;
        memcpy(&tx_buffer[1], rom_number, 8);
        tx_buffer_size = 10;
    } else {
        tx_buffer[0] = ONEWIRE_CMD_SKIP_ROM;
        tx_buffer[1] = DS18B20_CMD_READ_SCRATCHPAD;
        tx_buffer_size = 2;
    }

    ESP_RETURN_ON_ERROR(onewire_bus_write_bytes(handle, tx_buffer, tx_buffer_size),
                        TAG, "error while sending read scratchpad command");
    ESP_RETURN_ON_ERROR(onewire_bus_read_bytes(handle, (uint8_t *)&scratchpad, sizeof(scratchpad)),
                        TAG, "error while reading scratchpad command");

    ESP_RETURN_ON_FALSE(onewire_check_crc8((uint8_t *)&scratchpad, 8) == scratchpad.crc_value, ESP_ERR_INVALID_CRC,
                        TAG, "crc error");

    static const uint8_t lsb_mask[4] = { 0x07, 0x03, 0x01, 0x00 };
    uint8_t lsb_masked = scratchpad.temp_lsb & (~lsb_mask[scratchpad.configuration >> 5]); // mask bits not used in low resolution
    *temperature = (((int16_t)scratchpad.temp_msb << 8) | lsb_masked)  / 16.0f;

    return ESP_OK;
}

esp_err_t ds18b20_set_resolution(onewire_bus_handle_t handle, const uint8_t *rom_number, ds18b20_resolution_t resolution)
{
    ESP_RETURN_ON_FALSE(handle, ESP_ERR_INVALID_ARG, TAG, "invalid 1-wire handle");

    ESP_RETURN_ON_ERROR(onewire_bus_reset(handle), TAG, "error while resetting bus"); // reset bus and check if the device is present

    uint8_t tx_buffer[10];
    uint8_t tx_buffer_size;

    if (rom_number) { // specify rom id
        tx_buffer[0] = ONEWIRE_CMD_MATCH_ROM;
        tx_buffer[9] = DS18B20_CMD_WRITE_SCRATCHPAD;
        memcpy(&tx_buffer[1], rom_number, 8);
        tx_buffer_size = 10;
    } else {
        tx_buffer[0] = ONEWIRE_CMD_SKIP_ROM;
        tx_buffer[1] = DS18B20_CMD_WRITE_SCRATCHPAD;
        tx_buffer_size = 2;
    }

    ESP_RETURN_ON_ERROR(onewire_bus_write_bytes(handle, tx_buffer, tx_buffer_size),
                        TAG, "error while sending read scratchpad command");

    tx_buffer[0] = 0;
    tx_buffer[1] = 0;
    tx_buffer[2] = resolution;
    ESP_RETURN_ON_ERROR(onewire_bus_write_bytes(handle, tx_buffer, 3),
                        TAG, "error while sending write scratchpad command");

    return ESP_OK;
}