.cpp line 274

[spresley]

I am currently translating this library for nRF52832
Could anyone explain the reason for the request for 24 bytes followed by a read for 28 bytes, is this an error?

Wire.requestFrom(addrBME280, 24);
for (count = 0; count < 28; count++) { // first 28 bytes we can process like this
compParams.compArray[count] = Wire.read();
}

[hallard]

I'm also interested in, because the buffer compArray is declared as 20 bytes

union compParams_u
{
   uint8_t        compArray[20];
   compParams_ts  compStruct;
};

but compArray is not used anywhere so I think this part of code is useless

[Kwenchana]

Should be 24 from 0x88 to 0x9F, it's also missing the last humidity calibration H6 byte should be 8 total from 0xE1 to 0xE7, compArray is a union to compParams_ts

void BME280Class::readCompensationParams(void) {
  
  uint8_t count;
  uint16_t regE5, regE6;
  
  Wire.beginTransmission(addrBME280);
  Wire.write(regCalibStart);
  Wire.endTransmission();
  Wire.requestFrom(addrBME280, 24);
  for (count = 0; count < 24; count++) {  // first 24 bytes we can process like this
   compParams.compArray[count] = Wire.read();
  } 
  // then they go a bit strangely

  compParams.compStruct.dig_H1 = readRegister(0xA1);

  Wire.beginTransmission(addrBME280);
  Wire.write(regCalibStart2);
  Wire.endTransmission();
  Wire.requestFrom(addrBME280, 8);

  compParams.compStruct.dig_H2 = Wire.read();
  compParams.compStruct.dig_H2 |= (uint16_t)Wire.read() << 8;
  compParams.compStruct.dig_H3 = Wire.read();
  compParams.compStruct.dig_H4 = (uint16_t)Wire.read() << 4; // bits 11:4
  regE5 = Wire.read();
  compParams.compStruct.dig_H4 |= regE5 & 0b00001111; // bits 11:4
  compParams.compStruct.dig_H5 = regE5 >> 4;
  regE6 = Wire.read();
  compParams.compStruct.dig_H5 |= regE6 << 4;
  compParams.compStruct.dig_H6 = Wire.read(); 
}