Understanding Arduino I2C library for Nucleo-L432KC

[stm32_noob]

Hi,

I am trying to get the I2C1 bus in master mode up and running on the Nucleo-L432KC board and I can't get it working. I am using the Wire and TwoWire class which don't work with the way I have the code written (below). I have tried setting the SDA and SCL pins using the setSDA() and setSCL() functions. I've tried altering the pin maps as suggest on this web page (https://github.com/stm32duino/wiki/wiki/API#i2C). Still nothing, I've checked the pins with an oscilloscope and there's no activity.

I know I'm missing something here but I have no idea what it is. I'm I missing a configuration setting in the setup() function? If you know please let me know.

Thanks.

Example code:

Code: Select all

void setup() {
	Wire.setSDA(D4);
	Wire.setSCL(D5);
	Wire.begin();
}

void loop() {
	Wire.beginTransmission(0b0101110);
	Wire.write(0x00);
        Wire.write(0x7A);
        Wire.endTransmission();
        
        delay(250);
}

[fpiSTM]

Do you have pull up resistors on each I2C lines?

[stm32_noob]

Do you have pull up resistors on each I2C lines?

Yes I do, 4.7K on each line.

[fpiSTM]

OK. I've tested and it works on my side.

i2C_NucleoL432KC.png (19.94 KiB) Viewed 2983 times

Maybe a wiring issue or solder bridge. For example by default SB16 and SB18 are ON so D4/D5 are connected to A4/A5.

Just a note about the setSDA and setSCL in your sketch , you don't need to use it as by default D4 and D5 are the default pins of the Wire instance for Nucleo L432KC.

[stm32_noob]

OK. I've tested and it works on my side.
i2C_NucleoL432KC.png

Maybe a wiring issue or solder bridge. For example by default SB16 and SB18 are ON so D4/D5 are connected to A4/A5.

Just a note about the setSDA and setSCL in your sketch , you don't need to use it as by default D4 and D5 are the default pins of the Wire instance for Nucleo L432KC.

Thanks, that would explain the problem since I am using A4 and A5 for other stuff and had already initialized the IO.

[fpiSTM]

OK fine.
Please next time give us all information This would help a lot to understand your issue.
If you need A4 an A5 you can remove the SB as explained in the user manual. Then you will be able to use all pins.