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sinara-hw / Stabilizer

2-channel microcontroller servo with EEM and Ethernet based on STM32 CPU
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Header I2C bus should have pull-up resistors #109

Open nkrackow opened 2 years ago

nkrackow commented 2 years ago

The I2C bus going to the CPU GPIO header currently doesn't have pull-up resistors. If the CPU internal pull-ups are not enabled this leads to a bus error if no mezzanine with a pull-up on the I2C lines is plugged in. But the CPU internal pull-ups are also too large for nominal I2C spec.

gkasprow commented 2 years ago

This was done on purpose because these pins are also GPIOs. I added pull-ups on the mezzanines already.

jordens commented 2 years ago

The use case is without a mezzanine, where we'd want to probe for mezzanine presence. The CPU GPIO pullups are so weak that they may cause spurious ACK.