i2c1 no pull-up

[guansonghuang]

hello,my custom board using stm32mpa35faf7 i2c1, but I forget add externel pull-up resitors.

PD12--->I2C1_SCL

PE8 ---->I2C1_SDA

Now  ths i2c seems don't work.

please help me

[KnarfB]

In general, this needs to be fixed by adding the missing pull-ups.

Just for testing, it may work configuring the internal pull-ups on I2C1_SDA and I2C1_SCL in CubeMX GPIO Settings. The internal pull-ups are generally too weak, but better than nothing. 

You may also increase the Rise Time in CubeMX and ideally watch the singnals on a scope. 

And, surely you should use the slowest mode (standard mode). 

hth

KnarfB

[guansonghuang]

I reconfig  the dts tree of i2c1,use inner pull-up and 1K baurate seems not work too

[KnarfB · Accepted solution]

drive-push-pull is wrong for I2C. It is always drive-open-drain

hth

KnarfB