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Merge branch 'sht4x_minimal' of gitlab.com:HDIoT/smart_household/wired_sensors/iaq_wired_sensor into sht4x_minimal

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This commit is contained in:
David Žaitlík 2021-06-13 11:59:58 +02:00
commit ec5992d368
4 changed files with 54 additions and 0 deletions
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22
fw/Core/Inc/crc8.h Normal file
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@ -0,0 +1,22 @@
/*
* crc.h
*
* Created on: Jun 9, 2021
* Author: user
*/
#ifndef INC_CRC8_H_
#define INC_CRC8_H_
#include "stdint.h"
/*
* Definitions & macros
*/
#define CRC8_POLYNOMIAL 0x31
#define CRC8_INIT 0xFF
uint8_t crc8_calculate(const uint8_t *data, uint16_t count);
#endif /* INC_CRC8_H_ */

3
fw/Core/Inc/sht4x.h
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@ -10,7 +10,9 @@
#include "stdint.h"
#include "stm32l0xx_ll_i2c.h"
#include "stm32l0xx_ll_utils.h"
#include "i2c.h"
#include "crc8.h"
/*
* Defines & macros
@ -24,6 +26,7 @@
#define SHT4X_OK 0
#define SHT4X_ERROR -1 // generic error
#define SHT4X_CRC8_ERROR -2 // checksum failed
/*
* Data types

28
fw/Core/Src/crc8.c Normal file
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@ -0,0 +1,28 @@
/*
* crc.c
*
* Created on: Jun 9, 2021
* Author: user
*/
#include "crc8.h"
/* Stolen from Sensirion SCD4x datasheet, section 3.11 */
uint8_t crc8_calculate(const uint8_t *data, uint16_t count)
{
uint16_t current_byte;
uint8_t crc = CRC8_INIT;
uint8_t crc_bit;
/* calculates 8-Bit checksum with given polynomial */
for (current_byte = 0; current_byte < count; ++current_byte) {
crc ^= (data[current_byte]);
for(crc_bit = 8; crc_bit > 0; --crc_bit) {
if (crc & 0x80) {
crc =(crc << 1) ^ CRC8_POLYNOMIAL;
} else {
crc = (crc << 1);
}
}
}
return crc;
}

1
fw/Core/Src/sht4x.c
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@ -34,6 +34,7 @@ int8_t sht4x_measure(int *temperature, int *relative_humidity)
if (result != I2C_OK) {
return SHT4X_ERROR;
}
// TODO checksum
// Convert to T and RH; taken directly from pseudocode in SHT4x datasheet, page 3
uint32_t t_ticks = (buffer[0] << 8) + buffer[1];
uint32_t rh_ticks = (buffer[3] << 8) + buffer[4];