Hello Brad, El jue, 11 jul 2024 a las 12:25, Brad Spencer (<b...@anduin.eldar.org>) escribió: > > Ramiro Aceves <ea1...@gmail.com> writes: > > [snip] > > > Just a probably silly question: If I want to read the sensor that is > > being used by the bmh280thp driver, should I stop the driver first or > > the sensor can be inquired by the driver and my program ? > > > > Regards. > > Ramiro. > > > That question is device and driver dependent, but just speaking > generally, you would not want the kernel driver present if you are > messing with the device from userland. If you used modules, simply > unload it, or don't load it in the first place. You can probably also > use 'drvctl -d <device>' to detach the driver. For the Bosch 280 > devices, you can probably get away with not doing this, as there is very > little set up that the kernel driver does and there isn't any sort of > periodic update mode that is used that might have a kernel thread > polling the device. As long as you didn't try running envstat at the > same time you were messing with the device from userland, you may be > fine. The kernel driver only holds a i2c lock on the device when it is > doing a i2c read or write. >
I greatly appreciate the extensive and detailed response. At this stage all of this is aimed to do some programming exercise on NetBSD and learn how to interact with the C functions before I can do something really useful. > > On the BM[EP]280 device itself.... depending on what you are trying to > actually do... there are chip specific values that much be read out of > each chip individually and used in the raw value -> usable value > conversion routines. These values are factory set and unique to each > chip. You can look at the source for the kernel driver and see how > these values are pulled out of the chip in the attach function. To get > a usable output you need these calibration values and the conversion > algorithm which is published in the Bosch data sheet in order to get a > usable values from the sensor. All other drivers for other devices, > like the Ardunio, will do something simular. The Bosch 280 is more > complicated in this respect then most of the devices it competes with in > that the consumer of the device's raw output must apply chip specific > calibration when converting the raw values to something useable. > > Yes I know... I have a BME280, SGP30 and SDC40 sensors connected to an Atmel Atmega328 with 2x16 char display (Arduino nano cheap chineese board) that I programmed with avr-lib and gcc C compiler. I used some github libraries for the display and BME280 and adapted some code from Sensirion for the other chips. So I think I can reuse parts of it just in case. Those chips datasheets are a bit "diabolical" :-) Thanks so much. Ramiro. > > > > -- > Brad Spencer - b...@anduin.eldar.org - KC8VKS - http://anduin.eldar.org >
