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#define BME280_ADDR 0xEC // 111011xR /* registers */ #define BME280_RESET 0xE0 #define BME280_CTRL_HUM 0xF2 #define BME280_STATUS 0xF3 #define BME280_CTRL_MEAS 0xF4 #define BME280_CONFIG 0xF5 #define BME280_PRESS_MSB 0xF7 /* values */ #define BME280_CFG_OSRSH 0x01 #define BME280_CFG_OSRST 0x01 #define BME280_CFG_OSRSP 0x01 #define BME280_CFG_T_SB 0x04 /* every 500 ms */ #define BME280_CFG_FILT 0x00 #define BME280_MODE_NORMAL 0x03 #define BME280_MODE_SLEEP 0x00 #define BME280_MODE_FORCED 0x01 void BME280_init(void) { uint8_t tmp; /* reset */ write_reg(BME280_ADDR, BME280_RESET, 0xB6); HAL_Delay(2); tmp = read_reg(BME280_ADDR, BME280_STATUS); while ((tmp & 0x1) != 0) { /* wait until NVM reading is finished */ tmp = read_reg(BME280_ADDR, BME280_STATUS); } /* read cal data */ BME280_read_cal_data(); /* configure */ tmp = ((BME280_CFG_OSRST & 7) << 5) || ((BME280_CFG_OSRSP & 7) << 2) || (BME280_MODE_NORMAL & 3); write_reg(BME280_ADDR, BME280_CONFIG, (((BME280_CFG_T_SB & 7) << 5) || ((BME280_CFG_FILT & 7) << 2))); write_reg(BME280_ADDR, BME280_CTRL_MEAS,tmp); write_reg(BME280_ADDR, BME280_CTRL_HUM, (BME280_CFG_OSRSH & 7)); write_reg(BME280_ADDR, BME280_CTRL_MEAS,tmp); } (The code tag doesn't seem to work.)   ... View more

I mask and OR the bits in the register. I also took a copy of your humidity compensation function to try, but it also gave zero for that raw value (0x5295).   ... View more

Raising the voltage from 1.8V to 3.3V changed the situation such that no reset values are seen anymore, but still humidity raw value is wrong, I think. I also set the ovarsampling for humidity to 1. The data read from the chip is: buff[0] uint8_t 0x48 (Hex) buff[1] uint8_t 0x87 (Hex) buff[2] uint8_t 0x0 (Hex) buff[3] uint8_t 0x85 (Hex) buff[4] uint8_t 0xeb (Hex) buff[5] uint8_t 0x0 (Hex) buff[6] uint8_t 0x52 (Hex) buff[7] uint8_t 0x95 (Hex) Since I have no idea what the raw values represent, I can't figure out whether they make sense or not. The compensation constants read from the chip are: digH[0] int32_t 75 digH[1] int32_t 397 digH[2] int32_t 0 digH[3] int32_t 783 digH[4] int32_t 50 digH[5] int32_t 30 The configuration registers contain: status uint8_t 0x4 (Hex) ctrl_meas uint8_t 0x27 (Hex) ctrl_hum uint8_t 0x1 (Hex) config uint8_t 0x1 (Hex) right after the data read.   ... View more

That was quick! I wrote my own driver. I tried both normal and forced mode. And I polled until status register has bits 0 and 3 reset before burst read of data registers. I don't remember the oversampling settings. But I checked (in normal mode) that when I read, the mode seemed to be sleeping mode. Is that how it works, or should the mode register contain the value written there? [edit] Oversampling settings are 0 for humidity, 1 for temperature and pressure. I'm trying to read about every 500 ms. And yes, in force mode trials I write force mode into  the config-register before each read attempt. But after one succesful read, should the register values to contain reset values (0x080000 or 0x8000)?       ... View more