I2C not working and documentation has dead link

[AshrafIbrahim03]

This is a two parter:

I've been trying to initialize an I2C led for my microbit to no avail. I keep getting an O90 error. It's the same story of trying to follow documentation and not getting it to work. My microbit is set up so that it uses the default pins for i2c. Here's the code that I'm using to try to get it to work:

#include "MicroBit.h"
#include "MicroBitI2C.h"

MicroBit uBit;
MicroBitI2C i2c(I2C_SDA0,I2C_SCL0);

int main() {
    uBit.init();
}

I'm really not sure why it wouldn't work as I'm pretty sure this is what the documentation says, from what I've gathered. I should also mention that I've gotten the I2C led to work with Microsoft Makecode, so I know that it's connected properly.

Additionally, on line 50 of MicroBitI2C.cpp there's a dead link.

Thanks!

[finneyj]

Hi @AshrafIbrahim03

Easy one I think. :)

The uBit singleton object already has an instance of MicroBitI2C inside it, ready to use.
So no need to create another one.

Just use uBit.i2c.xxxx

[AshrafIbrahim03]

Hey, thanks for the quick reply, I removed the MicroBitI2C object but still got the same problem. I'm actually looking at the return value from uBit.i2c.writeRegister and I'm getting back MICROBIT_I2C_ERROR. Is there any documentation on how to narrow down where that error may be coming from? I actually pulled all the values I used for my code from a dev board(that uses python), and I've verified it works in Makecode but the jump to C++ just isn't working out. I rewrote the code a bit so here's what it looks like now:

#include "MicroBit.h"

MicroBit uBit;

void turnOnLED(uint8_t deviceAddress, uint8_t regAddr, uint8_t regData) {
    int result = uBit.i2c.writeRegister(deviceAddress, regAddr,regData );
    if (result == MICROBIT_OK) {
        uBit.display.scroll("1:I2C Write Success");
        return;
    }else if (result == MICROBIT_I2C_ERROR) {
        uBit.display.scroll("1:I2C error");
        return;
    }
    
    
}

int main() {
    uBit.init();

    uint8_t deviceAddress = 0x74; // 7-bit slave address on I2C bus


    uint8_t regAddr = 0x02; // Control register address
    uint8_t regData = 0xFF; // Data to turn on the LED

    turnOnLED(deviceAddress, regAddr, regData);
    fiber_sleep(10000);
    uBit.display.print(ManagedString('A'));

    release_fiber();
}

Edit: I should also mention that I used the same values for addresses and turning on/off values here as in the other places I've verified it works.

[AshrafIbrahim03]

I also just realized I was using 8 bit integers for 16 bit values and changed my code accordingly but still get the same error. Here's the code with the corrections:

#include "MicroBit.h"

MicroBit uBit;

void turnOnLED(unsigned short deviceAddress, unsigned short regAddr,unsigned short regData) {
    int result = uBit.i2c.writeRegister(deviceAddress, regAddr,regData );
    if (result == MICROBIT_OK) {
        uBit.display.scroll("1:I2C Write Success");
        return;
    }else if (result == MICROBIT_I2C_ERROR) {
        uBit.display.scroll("1:I2C error");
        return;
    }
    
    
}

int main() {
    uBit.init();

    unsigned short deviceAddress = 0x74; // 7-bit slave address on I2C bus

    uint8_t regAddr = 0x02; // Control register address
    unsigned short regData = 0xFF; // Data to turn on the LED
    unsigned short en_mode = 2;  
    unsigned short be_en = 1;    
    unsigned short ce_temp = 2;  
    unsigned short on = en_mode * 64 + be_en * 32 + ce_temp * 8;

    turnOnLED(deviceAddress, regAddr, on);
    fiber_sleep(10000);
    uBit.display.print(ManagedString('A'));

    release_fiber();
}

[cpseager]

• @param address 8-bit I2C slave address [ addr | 0 ]

Try 0xD8 instead of 0x74

[AshrafIbrahim03]

Just got the same error changing the address to 0xd8. I should also add the datasheet for the device I'm using is here if that helps

[martinwork]

I think it's *2, so maybe 0xE8 is right.

Or do a scan.

    for (int addr = 0x08; addr < 0x78; ++addr)
    {
        int ret = uBit.i2c.write( addr << 1, NULL, 0, false);

        uBit.serial.printf( "write addr %x %d = %d\n", addr << 1, addr << 1, ret);
    }