Reading I2C EEPROM fail on NULEOF446RE

Mbed OS
1

Hello,

I’m trying to use a I2C EEPROM(24LC64) on a NULEOF446RE board but the read results are always wrong.
Could someone tell me what is wrong with this?
I’m using Mbed OS2.
SDA & SCL pins are pulled up by 2.2k resisters.
The EEPROM adress is A0(A0, A1 & A2 pins are tied to ground).
All pins are connected correctly.
And I don’t know why but with NUCLEO303RE, reading EEPROM succeed with totally the same code.

Here is my test code.

#include "mbed.h"

Serial pc(USBTX, USBRX);
I2C mem(D14, D15);

void writeEEPROM(unsigned int eeaddress, char *data, int size)
{
    char i2cBuffer[size + 2];
    i2cBuffer[0] = (unsigned char)(eeaddress >> 8); // MSB
    i2cBuffer[1] = (unsigned char)(eeaddress & 0xFF); // LSB

    for (int i = 0; i < size; i++) {
        i2cBuffer[i + 2] = data[i];
    }
    mem.start();
    int result = mem.write(0xA0, i2cBuffer, size + 2, false);
    wait_ms(6);
    mem.stop();
}

void readEEPROM(unsigned int eeaddress, char *data, int size)
{
    char i2cBuffer[2];
    i2cBuffer[0] = (unsigned char)(eeaddress >> 8); // MSB
    i2cBuffer[1] = (unsigned char)(eeaddress & 0xFF); // LSB

    mem.start();
    int result = mem.write(0xA0, i2cBuffer, 2, false);
    wait_ms(6);

    mem.read(0xA1, data, size);
    wait_ms(6);
    mem.stop();
}

int main()
{
    mem.frequency(400000);
    
    char wData[3] = {0,1,2};
    writeEEPROM(0, wData,3);
    
    char rData[3];
    readEEPROM(0, rData,3);
    pc.printf("%x, %x, %x\r\n",rData[0],rData[1],rData[2]);
}

With 446RE, I got 0, 0, 0.
With 303RE, I got 0, 1, 2.

Any advice would be appreciated.

Thank you.

2

Hi there,

I do not know why it works on F303, but from my point of view, you wrongly use the I2C API (MbedOs2 and documentation of MbedOS5 )

    mem.start(); // incorrect
    int result = mem.write(0xA0, i2cBuffer, size + 2, false);
    wait_ms(6);
    mem.stop(); // incorrect

See me answer here. For I2C::read() it is similar.

Edit: you also not check the results of these methods, in your code.

BR, Jan

3

Hi Jan,

The problem has been solved.
Thank you for your advise!

Jumpei