ROHM BM1390 Pressure sensor (BM1390GLV-Z) can measure pressures ranging from 300 hPa to 1300 hPa with configurable measurement averaging and an internal FIFO. The sensor does also provide temperature measurements although, according to the data sheet, sensor performs internal temperature compensation for the MEMS. Sensor does also contain IIR filter implemented in HW. The data-sheet says the IIR filter can be configured to be "weak", "middle" or "strong". Some RMS noise figures are provided in data sheet but no accurate maths for the filter configurations is provided. I actually asked if we can define 3db frequencies corresponding to these IIR filter settings - and I received values 0.452Hz, 0.167Hz, and 0.047Hz but I am not at all sure we understood each others with the HW colleagues... Hence, the IIR filter configuration is not supported by this driver and the filter is just configured to the "middle" setting. (at least for now) It would also be possible to not use IIR filter but just do some simple averaging. I wonder if it would make sense to implement the OVERSAMPLING value setting so that if this value is written, IIR filter is disabled and number of samples to be averaged is set to value requested by OVERSAMPLING. The data-sheet has a mention that if IIR is used, the number of averaged samples must be set to a fixed value. The FIFO measurement mode (in sensor hardware) is only measuring the pressure and not the temperature. The driver measures temperature when FIFO is flushed and simply uses the same measured temperature value to all reported temperatures. This should not be a problem when temperature is not changing very rapidly (several degrees C / second) but allows users to get the temperature measurements from sensor without any additional logic. This driver has received limited amount of testing this far. It's in a state 'works on my machine, for my use cases' - and all feedback is appreciated! Matti Vaittinen (3): dt-bindings: Add ROHM BM1390 pressure sensor iio: pressure: Support ROHM BU1390 MAINTAINERS: Add ROHM BM1390 .../bindings/iio/pressure/rohm,bm1390.yaml | 52 + MAINTAINERS | 6 + drivers/iio/pressure/Kconfig | 9 + drivers/iio/pressure/Makefile | 1 + drivers/iio/pressure/rohm-bm1390.c | 944 ++++++++++++++++++ 5 files changed, 1012 insertions(+) create mode 100644 Documentation/devicetree/bindings/iio/pressure/rohm,bm1390.yaml create mode 100644 drivers/iio/pressure/rohm-bm1390.c base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c -- 2.41.0 -- Matti Vaittinen, Linux device drivers ROHM Semiconductors, Finland SWDC Kiviharjunlenkki 1E 90220 OULU FINLAND ~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~ Simon says - in Latin please. ~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~ Thanks to Simon Glass for the translation =]
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