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SCD4x CRC check

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mj 2022-01-02 16:16:47 +01:00
parent 98e6a7f93d
commit e6e97a2547
2 changed files with 19 additions and 10 deletions
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7
fw/Core/Src/main.c
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@ -331,9 +331,10 @@ int main(void)
/* Read SCD4x data (if connected) */ /* Read SCD4x data (if connected) */
if (scd4x_is_connected == 1) if (scd4x_is_connected == 1)
{ {
scd4x_read_measurement(&CO2, if (scd4x_read_measurement(&CO2, &T_SCD4x, &RH_SCD4x) != SCD4X_OK) {
&T_SCD4x, /* read failed, either I2C fail or CRC error */
&RH_SCD4x); // TODO something
}
if (CO2 > 0) { if (CO2 > 0) {
co2_valid = 1; co2_valid = 1;
} else { } else {

22
fw/Core/Src/scd4x.c
View File

@ -80,11 +80,9 @@ int8_t scd4x_read_measurement(uint16_t *co2, int16_t *temperature, uint16_t *rel
buffer[0] = SCD4X_READ_MEASUREMENT >> 8; buffer[0] = SCD4X_READ_MEASUREMENT >> 8;
buffer[1] = SCD4X_READ_MEASUREMENT & 0x00ff; buffer[1] = SCD4X_READ_MEASUREMENT & 0x00ff;
result = i2c_transmit(SCD4X_I2C_ADDRESS<<1, buffer, 2); result = i2c_transmit(SCD4X_I2C_ADDRESS<<1, buffer, 2);
if (result != I2C_OK) {
// TODO: Proc to vraci NACK? Vyresit.
/*if (result != I2C_OK) {
return SCD4X_ERROR; return SCD4X_ERROR;
}*/ }
uart_enable_interrupts(); uart_enable_interrupts();
LL_mDelay(1); // 10 ms should be enough LL_mDelay(1); // 10 ms should be enough
uart_disable_interrupts(); uart_disable_interrupts();
@ -95,12 +93,22 @@ int8_t scd4x_read_measurement(uint16_t *co2, int16_t *temperature, uint16_t *rel
{ {
return SCD4X_ERROR; return SCD4X_ERROR;
} }
/* Convert to T and RH; taken directly from pseudocode in SHT4x datasheet, page 3 */
// TODO checksum
// Convert to T and RH; taken directly from pseudocode in SHT4x datasheet, page 3
uint32_t co2_ticks = (buffer[0] << 8) + buffer[1]; uint32_t co2_ticks = (buffer[0] << 8) + buffer[1];
uint8_t co2_crc = buffer[2];
uint32_t t_ticks = (buffer[3] << 8) + buffer[4]; uint32_t t_ticks = (buffer[3] << 8) + buffer[4];
uint8_t t_crc = buffer[5];
uint32_t rh_ticks = (buffer[6] << 8) + buffer[7]; uint32_t rh_ticks = (buffer[6] << 8) + buffer[7];
uint8_t rh_crc = buffer[8];
/* check CRC-8 checksum */
uint8_t crc_correct = crc8_calculate(buffer, 2) == co2_crc;
crc_correct &= crc8_calculate(buffer + 3, 2) == t_crc;
crc_correct &= crc8_calculate(buffer + 6, 2) == rh_crc;
if (!crc_correct) {
return SCD4X_CRC8_ERROR;
}
/* copy to output variables */
int t_degC = -450 + 10 * 175 * t_ticks / 65535; int t_degC = -450 + 10 * 175 * t_ticks / 65535;
int rh_pRH = 100 * rh_ticks / 65535; int rh_pRH = 100 * rh_ticks / 65535;
if (rh_pRH > 100) { if (rh_pRH > 100) {