CONFLICT WHEN USING I2C1 STM32F4 DISCOVERY

[bacnk]

I use STM32F4 Discovery, and when using I2C1 for communication, I encounter a situation where the chip becomes unresponsive while using UART and during operation with I2C1. When I use other I2C interfaces, it works normally. I want to understand what is causing I2C1 to make the chip unresponsive.

When I use other I2C interfaces, the response is only within 100ms, but when using this I2C interface, the response takes several seconds

thanks you

[Andrew Neil]

Have you checked the board's User Manual and/or Schematics to see if there's anything else on that pin?

Example just now:

https://community.st.com/t5/stm32-mcus-products/low-voltage-for-logic-high-on-nucleo-g431kb/td-p/737306

[Imen.D]

Hello @bacnk 

Make sure that there are no resource conflicts between I2C1 and other peripherals and that I2C1 is correctly initialized and configured in your code.

I advise you to enable timeout register and use an oscilloscope or logic analyzer to monitor the I2C bus.

[bacnk]

I use stm32f4 discovery kit, I configure i2c 2,3 similarly but when using i2c 2,3 it is normal, but when using i2c1 I have the problem of slow response chip. I use uart to check response time

[bacnk]

I use resistor connected to 3v3, do I need to configure pull up in the code?

[waclawek.jan]

> I use resistor connected to 3v3, do I need to configure pull up in the code?

No, but the value of the external resistor matters, together with its capacitance.

> the chip becomes unresponsive while using UART and during operation with I2C1

Which chip? How do you know it's unresponsive?

Do you observe the SDA/SCL signals using oscilloscope or logic analyzer (LA)?

As @Imen.D pointed out above, there may be pins which are already used on the board. In particular, I2C1_SDA can be on pins PB7/PB9, I2C1_SCL on PB6/PB8, but note, that is on-board I2C device on PB6/PB9 (the CS43L22 audio codec) so if you use these pins, note that the on-board I2C device may interfere. See manual and schematics of the Disco board.

JW

[Andrew Neil]

Again, have you checked the board's User Manual and/or Schematics to see if there's anything else on those pins?

ie, have you checked for conflicts on the board?

Use an oscilloscope to see what's actually happening on the wires.

[Andrew Neil]

Please show a schematic.

Trying to describe electronic circuits in text is really ineffective - that's why we have schematics!