Problems with I2C1 on the RAK3172 module

LPWAN Modules / EVBs
1

Hello RAK Wireless Support Team.

I’m trying to migrate an STM32WLE5CCU6 project that was initially developed in STM32CubeIDE to the RAK3172 module.
I’m having problems with the I2C interface, in the original project I’m using the I2C1 interface on PB6 SCL and PB7 SDA with a baudrate of 400 KHz. On the RAK3172 module PB6 and PB7 correspond to pins UART1_TX and UART1_RX respectively.
When programming the project in RAK3172 the I2C1 interface did not work, I looked at the SCL and SDA signals with a logic analyzer and the waveforms did not match the I2C signaling.
I tried changing to the I2C2 interface, using PA12 SCL and PAC11 SDA, that worked, but I noticed that I had left the baudrate at 100 KHz.
I decided to go back to I2C1, but lowering the baudrate to 100 KHz, I verified that it started working, but intermittently.
I was wondering if perhaps the UART1_TX and UART1_RX pins of the RAK3172 module are not “directly” connected to the PB6 and PB7 pins of the STM32WL5CCU6.
Could you tell me if something like that could explain this problem I’m seeing in I2C1?

Best Regards.

2

Welcome to RAK forum @Takahashi ,

I am not sure exactly what could be causing your issue? Could it be timing related?

As for the connection of PB6 and PB7, it is directly connected to STM32WL pins without any passive/active component in between.

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I found the cause of the problem.
I didn’t realize that I had configured another output signal on the same PB7 port.

Thank you very much for your attention and sorry for the inconvenience.

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