/* * Copyright (c) 2019, Erich Styger * All rights reserved. * * Driver for the SHT31 Temperature/Humidity sensor * * SPDX-License-Identifier: BSD-3-Clause */ #include "McuSHT31config.h" #include "McuSHT31.h" #include "McuGenericI2C.h" #include "McuUtility.h" #include /* for NULL */ #define SHT31_MEAS_HIGHREP_STRETCH 0x2C06 #define SHT31_MEAS_MEDREP_STRETCH 0x2C0D #define SHT31_MEAS_LOWREP_STRETCH 0x2C10 #define SHT31_MEAS_HIGHREP 0x2400 #define SHT31_MEAS_MEDREP 0x240B #define SHT31_MEAS_LOWREP 0x2416 #define SHT31_READSTATUS 0xF32D #define SHT31_CLEARSTATUS 0x3041 #define SHT31_SOFTRESET 0x30A2 #define SHT31_HEATEREN 0x306D #define SHT31_HEATERDIS 0x3066 /* status bits of the Status register (0xF32D) */ #define SHT31_STATUS_ALERT_PENDING (1<<15) /* 0: no pending alert, 1: at least one pending alert */ #define SHT31_STATUS_HEATER_ON (1<<13) /* 0: heater OFF, 1: heater ON */ #define SHT31_STATUS_RH_TRACKING_ALERT (1<<11) /* 0: no RH tracking alert, 1: alert */ #define SHT31_STATUS_T_TRACKING_ALERT (1<<10) /* 0: no T tracking alert, 1: alert */ #define SHT31_STATUS_SYSTEM_RESET (1<<4) /* 0: no reset detected since last clear status register command, 1: reset detected (hard reset, soft reset or supply fail */ #define SHT31_STATUS_CMD_STATUS (1<<1) /* 0: last command executed successfully; 1: last command not processed, it was either invalid, failed the internal command checksum */ #define SHT31_STATUS_WRITE_CRC_STATUS (1<<0) /* 0: checksum of last write transfer was correct, 1: checksum of last write transfer failed */ #define SHT31_CRC8_POLYNOMIAL 0x31 /* Seed for CRC polynomial */ #define SHT31_CRC8_INIT 0xFF /* Init value for CRC */ static uint8_t SHT31_GenerateCRC(uint8_t *data, uint8_t datalen) { /* calculates 8-Bit checksum with given polynomial */ uint8_t crc = SHT31_CRC8_INIT; uint8_t b; uint8_t i; for (i=0; i>8; buf[1] = cmd&0xff; return McuGenericI2C_WriteAddress(McuSHT31_CONFIG_I2C_ADDR, buf, sizeof(buf), NULL, 0); } uint8_t SHT31_ReadStatus(uint16_t *status) { uint8_t res; uint8_t cmd[2]; uint8_t stat[3]; uint8_t crc; cmd[0] = SHT31_READSTATUS>>8; cmd[1] = SHT31_READSTATUS&0xff; res = McuGenericI2C_ReadAddress(McuSHT31_CONFIG_I2C_ADDR, cmd, sizeof(cmd), stat, sizeof(stat)); if (res!=ERR_OK) { *status = 0; return res; } crc = SHT31_GenerateCRC(stat, 2); if (crc!=stat[2]) { return ERR_CRC; /* wrong CRC */ } *status = (stat[0]<<8)+stat[1]; /* ignore CRC */ return res; } uint8_t McuSHT31_Heater(bool on) { return SHT31_WriteCommand(on?SHT31_HEATEREN:SHT31_HEATERDIS); } uint8_t McuSHT31_Reset(void) { return SHT31_WriteCommand(SHT31_SOFTRESET); } uint8_t McuSHT31_ReadTempHum(float *temperature, float *humidity) { uint16_t ST, SRH; uint8_t readbuffer[6]; uint8_t res; uint8_t cmd[2]; cmd[0] = SHT31_MEAS_HIGHREP>>8; cmd[1] = SHT31_MEAS_HIGHREP&0xff; res = McuGenericI2C_ReadAddressWait(McuSHT31_CONFIG_I2C_ADDR, cmd, sizeof(cmd), McuSHT31_CONFIG_READ_WAIT_MS, readbuffer, sizeof(readbuffer)); if (res!=ERR_OK) { return res; } ST = (readbuffer[0]<<8)|readbuffer[1]; if (readbuffer[2] != SHT31_GenerateCRC(readbuffer, 2)) { return ERR_CRC; } SRH = (readbuffer[3]<<8)|readbuffer[4]; if (readbuffer[5] != SHT31_GenerateCRC(readbuffer+3, 2)) { return ERR_CRC; } /* source: https://github.com/adafruit/Adafruit_SHT31/blob/master/Adafruit_SHT31.cpp */ int32_t stemp = (int32)ST; /* simplified (65536 instead of 65535) integer version of: * temp = (stemp * 175.0f) / 65535.0f - 45.0f; */ stemp = ((4375 * stemp) >> 14) - 4500; *temperature = (float)stemp / 100.0f; /* source: https://github.com/adafruit/Adafruit_SHT31/blob/master/Adafruit_SHT31.cpp */ uint32_t shum = (uint32_t)SRH; /* simplified (65536 instead of 65535) integer version of: * humidity = (shum * 100.0f) / 65535.0f; */ shum = (625 * shum) >> 12; *humidity = (float)shum / 100.0f; return ERR_OK; } #if MCUSHT31_CONFIG_PARSE_COMMAND_ENABLED static uint8_t PrintStatus(const McuShell_StdIOType *io) { uint8_t buf[32]; float temperature, humidity; McuShell_SendStatusStr((unsigned char*)"SHT31", (unsigned char*)"Sensirion SHT31 sensor status\r\n", io->stdOut); McuUtility_strcpy(buf, sizeof(buf), (unsigned char*)"0x"); McuUtility_strcatNum8Hex(buf, sizeof(buf), McuSHT31_CONFIG_I2C_ADDR); McuUtility_strcat(buf, sizeof(buf), (unsigned char*)"\r\n"); McuShell_SendStatusStr((unsigned char*)" addr", buf, io->stdOut); if(McuSHT31_ReadTempHum(&temperature, &humidity)==ERR_OK) { McuUtility_NumFloatToStr(buf, sizeof(buf), temperature, 2); McuUtility_chcat(buf, sizeof(buf), '\xB0'); /* add '°' (ASCII 0xB0) it as single char, as with UTF-8 it might end up in two bytes inside a string */ McuUtility_strcat(buf, sizeof(buf), (unsigned char*)"C\r\n"); McuShell_SendStatusStr((unsigned char*)" temp", buf, io->stdOut); McuUtility_NumFloatToStr(buf, sizeof(buf), humidity, 2); McuUtility_strcat(buf, sizeof(buf), (unsigned char*)" RH\r\n"); McuShell_SendStatusStr((unsigned char*)" humidity", buf, io->stdOut); } else { McuShell_SendStatusStr((unsigned char*)" ERROR:", (unsigned char*)" *** ERROR reading sensor values\r\n", io->stdOut); } return ERR_OK; } static uint8_t PrintHelp(const McuShell_StdIOType *io) { McuShell_SendHelpStr((unsigned char*)"SHT31", (unsigned char*)"Group of SHT31 commands\r\n", io->stdOut); McuShell_SendHelpStr((unsigned char*)" help|status", (unsigned char*)"Print help or status information\r\n", io->stdOut); return ERR_OK; } #endif /* MCUSHT31_CONFIG_PARSE_COMMAND_ENABLED */ #if MCUSHT31_CONFIG_PARSE_COMMAND_ENABLED uint8_t McuSHT31_ParseCommand(const unsigned char* cmd, bool *handled, const McuShell_StdIOType *io) { uint8_t res = ERR_OK; if (McuUtility_strcmp((char*)cmd, McuShell_CMD_HELP) == 0 || McuUtility_strcmp((char*)cmd, "SHT31 help") == 0) { *handled = TRUE; return PrintHelp(io); } else if ( (McuUtility_strcmp((char*)cmd, McuShell_CMD_STATUS)==0) || (McuUtility_strcmp((char*)cmd, "SHT31 status")==0) ) { *handled = TRUE; res = PrintStatus(io); } return res; } #endif /* SHT31_CONFIG_PARSE_COMMAND_ENABLED */ void McuSHT31_Init(void) { /* noting to do */ } void McuSHT31_Deinit(void) { /* nothing to do */ }