Search code examples
arduinostm32i2ceeprom

I2C between EEPROM and Arduino working, not with STM32

This is driving me nuts for a couple of days now, so maybe you guys can give me some insights into what is going wrong.

I'm trying to read some data from an EEPROM (24LC16B) with an STM32(F0), but it just doesn't let me. I've tried an Arduino, which worked and does still work, so I do know that the wiring is correct.

This is my function to read the EEPROM data. (It is cut down to the very basis, just for testing): (Pastebin of my I2C_setup function)

uint16_t readEEPROMData(uint16_t deviceAddress, int memAddress){
    // Wait while I2C peripheral is not ready
    I2C_WaitForFlag(I2C_ISR_BUSY);

    // Start I2C write transfer for 2 bytes, do not end transfer (SoftEnd_Mode)
    I2C_TransferHandling(I2C1, 0xA2, 2, I2C_SoftEnd_Mode, I2C_Generate_Start_Write);
    I2C_WaitForFlag(I2C_ISR_TXIS);

    // For testing purpose, be sure to generate a stop command...
    I2C_TransferHandling(I2C1, 0xA2, 0, I2C_AutoEnd_Mode, I2C_Generate_Stop);

    return I2C_COMM_STATUS;
}

Here's an pastebin of the Arduino library I used.

I've used a logic analyzer to see how the communication is going, and now I really don't understand it. Here's a printscreen of the working Arduino version: Arduino EEPROM communication

And here's a printscreen of the STM32 communication: STM32 EEPROM communication

Logic analyzer exports (viewable with Saleae Logic)

As you can see, I'm using the same address (although I had to use 0xA2 with the STM32), and there are no weird things happening, besides the NACK. So what could possible be wrong?

Solution
    1. Confirm if all bus timing requirement are satisfied.
    2. Confirm if their is adequate delay after every write cycle (5 mS)
    3. Confirm is bus capacitance falls under permissible limit of I2C (400 pF - Theoretically).
    4. Confirm if the correct VCC is supplied

    As mentioned by you are interfacing EEPROM with MCU using cable you need to conform on capacitance.

    You can use an oscilloscope to check if their are any distortion in waveform. You can use a LCR meter to check the capacitance.

    Try reducing bus speed 25kHz to 50 kHz and check waveform. Try increasing the strength of pull resister.

    The problem with the wrong VCC capacity (4.2v instead of 5v for example) is, that the timing can be different to. (not fully verified, but it fixed the problem)