I2C in PA/PT8/16

[lucyperek]

Hi guys,

are there any special tricks not mentioned in the manual to operate this interface by non open drain pins? In a/m MCUs there is a possibility of remapping I2C pins from PA2/PA3 to PB6/PB7 which are not open drain.

So how can it work ? My software works correctly with these open drain pins but I need to use B6/B7. It is mentioned that they can serve as well this protocol if both devices on the bus are powered from the same supply voltage. Ok, that's clear. But this communication doesn't want to work. On oscilloscope I observe strange behaviour of SDA line (its I/O pin was set as input).

So does anybody know what to do with it ?

Regards

Jacek

[lucyperek]

Hi Vicent,

I have simply developed a universal software simulation of I2C. Can be implemented on other ports and MCUs.

brgds

Jacek

[lucyperek]

Dear Vicent,

later on investigating some other threads I have encountered one with NXP reply with some erratas... By curiosity I have looked at them. Haha ! one of the topics deals with a/m problem. The "workaround" advice is simple : "do not use B7,B6 as I2C interface as it is badly designed (not open drain)".

Of course we all make mistakes but it would be nice to make correction in RM to avoid confusion. Because the SHxx in TSSOP packages are nearly not available I have to prepare for countertypes (PA/PT/PL will work) the only problem was that SH uses B7,B6 for I2C and I do not intend to change PCB design. So I work now on I2C software simulation.

[vicentegomez]

Did you add the external pull-ups?

Thanks