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ketan_vd
Associate
August 11, 2024
Question

I2C3 Slave need to re-power to work

  • August 11, 2024
  • 3 replies
  • 787 views

Hi All,

I am Ketan, and I am implementing own driver for STM32F4 device. I have STM32F4-DISCO Development, everything looks fine when I2C talks on-board slave device (CS43L22) but when I2C talk to external slave, which is connected thorough Jumper wire, it seems start condition not able to generate. most of time, I switch off the external slave and switch on, then works fine. but without power off external slave, looks start condition is not able to generate. I am not suspecting driver issue, because on-board slave device address able to read.

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3 replies

TDK
TDK
August 11, 2024

Some possibilities:

  • Ensure external pullups are present.
  • Ensure board is powered.
  • Ensure pins are connected correctly.
  • Ensure slave address is correct. It should be left-shifted.
  • Use a logic analyzer to see what is happening on the line.
  • If bus is interrupted mid-transaction, slave could be stuck. Toggle SCL 9 times as a GPIO to reset the bus.
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ketan_vdAuthor
Associate
August 11, 2024

Hi,

Thank you for reply. as I mention, external slave device also working fine but only when restart the power cycle. that means pins are connected correctly, board is powered, slave address is correct. 

I feel, I didn't connected external pullups register but instead off, I am using GPIO pullups configuration while initializing the pins.

TDK
TDK
August 12, 2024

Debug the code, figure out why it's not working, or at least how. Do HAL functions return HAL_OK? Where in the process does the code fail? Perhaps show some code. Are you respecting startup times? Do you have a logic analyzer to further debug?

> I feel, I didn't connected external pullups register but instead off, I am using GPIO pullups configuration while initializing the pins.

I can't decipher this. Does this mean external pullups in the region of 1-5 kOhm are present or not?

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