83 lines
2.4 KiB
C
83 lines
2.4 KiB
C
#include "scd30.h"
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#include "driver/i2c_master.h"
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#include <string.h>
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#include <stdio.h>
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#define SCD30_I2C_ADDRESS 0x61
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#define SCD30_CMD_START_MEASUREMENT 0x0010
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#define SCD30_CMD_READ_DATA 0x0300
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#define SCD30_CMD_READY_STATUS 0x0202
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// Private function to calculate CRC-8
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static uint8_t calculate_crc8(const uint8_t *data, size_t len) {
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const uint8_t polynomial = 0x31;
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uint8_t crc = 0xFF;
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for (size_t i = 0; i < len; i++) {
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crc ^= data[i];
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for (uint8_t bit = 0; bit < 8; bit++) {
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if (crc & 0x80) {
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crc = (crc << 1) ^ polynomial;
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} else {
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crc <<= 1;
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}
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}
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}
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return crc;
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}
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void scd30_init(void) {
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i2c_master_config_t i2c_config = {
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.scl_wait_us = 150000 // Clock stretching
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};
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i2c_master_init(I2C_NUM_0, &i2c_config);
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}
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void scd30_start_measurement(void) {
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uint8_t command[5] = {
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(SCD30_CMD_START_MEASUREMENT >> 8) & 0xFF,
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SCD30_CMD_START_MEASUREMENT & 0xFF,
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0x00, 0x10, // Argument for continuous measurement
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0x00 // Placeholder for CRC
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};
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command[4] = calculate_crc8(&command[2], 2);
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i2c_master_write_to_device(I2C_NUM_0, SCD30_I2C_ADDRESS, command, sizeof(command), 1000 / portTICK_PERIOD_MS);
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}
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int scd30_read_data(scd30_data_t *data) {
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uint8_t ready_command[2] = {
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(SCD30_CMD_READY_STATUS >> 8) & 0xFF,
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SCD30_CMD_READY_STATUS & 0xFF
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};
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uint8_t ready_status[3];
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// Poll until data is ready
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do {
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i2c_master_write_read_device(I2C_NUM_0, SCD30_I2C_ADDRESS, ready_command, sizeof(ready_command), ready_status, sizeof(ready_status), 1000 / portTICK_PERIOD_MS);
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} while (ready_status[1] != 0x01);
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uint8_t read_command[2] = {
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(SCD30_CMD_READ_DATA >> 8) & 0xFF,
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SCD30_CMD_READ_DATA & 0xFF
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};
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uint8_t buffer[18];
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// Read 18 bytes of data
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i2c_master_write_read_device(I2C_NUM_0, SCD30_I2C_ADDRESS, read_command, sizeof(read_command), buffer, sizeof(buffer), 1000 / portTICK_PERIOD_MS);
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// Validate CRC for each pair of data
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for (int i = 0; i < 18; i += 3) {
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if (calculate_crc8(buffer + i, 2) != buffer[i + 2]) {
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return -1; // CRC error
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}
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}
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// Parse data
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data->co2 = (float)((buffer[0] << 8) | buffer[1]);
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data->temp = (float)((buffer[3] << 8) | buffer[4]);
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data->humidity = (float)((buffer[6] << 8) | buffer[7]);
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return 0; // Success
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}
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