I need information about the I2 C bus interface whether and which pull-up resistors are used
Hi, could you please provide us with the specific device type you are referring to?
BalenaFin V1.0 -8GB
Which I2C bus are you referring to? There is one that is commonly used i.e. the I2C1 bus, but there is also another which is typically connected to EEPROM, CSI, DSI, etc.
In either case, you can find more information about how the I2C pins are connected in the schematics that we have published on GitHub.
You can find the schematic for the fin here - https://github.com/balena-io/balena-fin/blob/master/documentation/PDF/balenaFin/v1.1/schematics/20173009_balena-fin_v10.pdf
which i2 c bus is on the 40-pin connector?
Hi Bernd, the HAT connector (40-pin) exposes both i2c buses as you can see here: https://pinout.xyz/pinout/i2c
the i2c0 bus is exposed to allow the videocore element of the compute module SoC to read EEPROM data from the HATs, and is not exposed to userspace by default.
i2c1 bus (GPIO2 and GPIO3 pins) is exposed to userspace by default and is probably what you are targeting.
In both cases, balenaFin just routes the pins from the Raspberry Pi Compute Module 3+ Lite to the header, so you can refer to the datasheet for the Raspberry Pi Compute Module 3 Lite (CM3L) https://www.raspberrypi.org/documentation/hardware/computemodule/datasheets/rpi_DATA_CM_1p0.pdf
here is also the balenaFin datasheet: https://github.com/balena-io/balena-fin/blob/master/documentation/PDF/balenaFin/v1.1/schematics/20173009_balena-fin_v10.pdf