GSoC'2018 Project: https://summerofcode.withgoogle.com/projects/#6691473790074880 Mentor: Daniel Baluta BME680 is a 4-in-1 sensor with temperature, pressure, humidity & gas sensor with I2C and SPI interface support. The sensor has various calibration parameters[1] to be used with raw adc data in the compensation functions[2] to evaluate the correct compensated reading. These calibration parameters are are programmed into the devices’ non-volatile memory (NVM) during production and cannot be altered by the customer. So, we are required to read those parameters once(suitably at probe) and use it in the compensation functions. But now the problem arises that these compensation functions, calibration parameters, their addresses are *not* provided in the datasheet and instead provided by Bosch Sensortec in their Github API[3]. The Github API has a LICENSE file[4] around 40 lines which I presume kernel community won't entertain. Therefore, we contacted Bosch Sensortec thrice 2 weeks ago and got no response so far. We stated all the problems relating to Lincensing & missing calibration info from the datasheet. I got to know about these missing information from the Github API and also looking at the various sensors supplied by the company such as BMP280, BME280 etc. After using their compensation function in my driver I get correct readings. But we can't simply use these function without their permission! For instance: I got a temperature reading of: 3254 and if this sensor has a similar resolution as that of BMP280 which 0.01 degC then it is absolutely correct. 3254 * 0.01 = 32.54 degC This 0.01 degC resolution was mentioned in the BMP280 datasheet but there is no such information in the BME680 datasheet nor in the Github API. This is what I have assumed since after testing pressure & humidity also revealed similar readings and there is some possibilty that they could have same output resolution as they belong to the same family of sensors. For now I have placed the sensor in the IMU but this is not an IMU and there is no such sensor(4-in-1) in the whole IIO subsystem. So, where should it be placed ? Would it be worthwhile to create a new subdirectory "environmental" since it is a environmental sensor ? The sensor also has an IIR filter to remove short term fluctuations from the temperature and pressure readings. It has various filter coefficients and I have chosen the middle valued coefficient(15) from the table for now. What filter coefficient is most appropriate for the device ? Again, I asked this question too from Bosch since they discuss all these optimal selection of filter in "3.4 Filter selection" Pg 14 BMP280. I have used regmap API and therefore we don't need the LSB address of data registers as we only care about the MSB address of the data register and regmap_bulk_read() handles everything fine. So, would it be worthwhile to add these LSB macros definition too ? They certainly will never be used! For now, this series doesn't include any of the copyrighted code from Bosch and I have just added them as a dummy function. I have mentioned more detailed summary in my blog[5] and would love any feedback on it. If anyone has contacts to Bosch Sensortec GmbH then please let me know. [1] https://github.com/BoschSensortec/BME680_driver/blob/313a58a9c57ad86c8df06c98521579c6cb695999/bme680_defs.h#L410 [2] https://github.com/BoschSensortec/BME680_driver/blob/master/bme680.c#L876 [3] https://github.com/BoschSensortec/BME680_driver [4] https://github.com/BoschSensortec/BME680_driver/blob/master/LICENSE [5] https://himanshujha199640.wordpress.com/2018/06/14/0x01bme680-temperature-channel/ Himanshu Jha (3): iio: imu: bme680: Add initial support for Bosch BME680 iio: imu: bme680: Add temperaure, pressure & humidity channels iio: imu: bme680: Add ACPI support drivers/iio/imu/Kconfig | 1 + drivers/iio/imu/Makefile | 1 + drivers/iio/imu/bme680/Kconfig | 32 +++ drivers/iio/imu/bme680/Makefile | 6 + drivers/iio/imu/bme680/bme680.h | 11 + drivers/iio/imu/bme680/bme680_core.c | 542 +++++++++++++++++++++++++++++++++++ drivers/iio/imu/bme680/bme680_i2c.c | 62 ++++ drivers/iio/imu/bme680/bme680_spi.c | 49 ++++ 8 files changed, 704 insertions(+) create mode 100644 drivers/iio/imu/bme680/Kconfig create mode 100644 drivers/iio/imu/bme680/Makefile create mode 100644 drivers/iio/imu/bme680/bme680.h create mode 100644 drivers/iio/imu/bme680/bme680_core.c create mode 100644 drivers/iio/imu/bme680/bme680_i2c.c create mode 100644 drivers/iio/imu/bme680/bme680_spi.c -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
