How can I use two I2C modules?

[kahlenberg]

Hi,

I want to measure CO2 in different locations using two similar CO2 sensor (MiCS-VZ-89TE). I can communicate with the sensor over I2C0.

But because two sensors have exactly the same I2C address, I cannot connect the second sensor to the same I2C0 module.

How can I activate I2C1 and where are the SDA and SCL pins of I2C1?

[Vidar Berg]

Hi,

The default pin assignments for SDA and SCL are usually defined in board files. For instance, here if you use the '52840dk_nrf52840': https://github.com/nrfconnect/sdk-zephyr/blob/main/boards/arm/nrf52840dk_nrf52840/nrf52840dk_nrf52840-pinctrl.dtsi#L62.

Best regards,

Vidar

[kahlenberg]

Ok, thank you for answer. I connected the sensor to I2C1 pins P0.30 and P0.31, I cannot communicate with sensor.

When I connect the sensor to I2C0 over P0.26 and P0.27, I can communicate.

Is there any other settings in devicetree overlay or CONFIG variables?

In my devicetree overlay I have:

&i2c1 {
    status = "okay";
    vz89te1: vz89te@70 {
        compatible = "i2c-device";
        label = "MiCS-VZ-89TE-1";
        reg = <0x70>;
    };
};

status = "okay", because, as default in devicetree file, status = "okay" is commented, so I wrote it in overlay file.

[Vidar Berg]

Are you able to debug your driver to see where it fails when you select i2c1? It may also be a good idea to check the TWIM0/1 registers to see if they are being configured correctly.

[kahlenberg]

I am able to debug it, but I don't know where to look/check.

It seems TWIM0 and TWIM1 registers are configured correctly, at least pin numbers in PSEL are correct.
But in Address (is it a register?) is wrong. At TWIM0 it is 0x70, and at TWIM1 it is 0.

My devicetree overlay snippet:

&i2c0 {
    vz89te0: vz89te0@70 {
        compatible = "i2c-device";
        label = "MiCS-VZ-89TE-0";
        reg = <0x70>;
    };
};

&i2c1 {
    status = "okay";
    vz89te1: vz89te1@70 {
        compatible = "i2c-device";
        label = "MiCS-VZ-89TE-1";
        reg = <0x70>;
    };
};

[Vidar Berg]

The ADDRESS register is set when the i2c driver starts a transaction, so the fact that it is not set could indicate that something failed earlier in the init process.

Do you have debug logs enabled (CONFIG_LOG=y) to see if the driver reports any errors?

[kahlenberg]

When I activate logs, I receive the following error in NRF Terminal:

[00:00:01.506,469] <err> i2c_nrfx_twi: Error on I2C line occurred for message 0

I don't know what it means.

In the nRF52840_DK_User_Guide_20201203 Document, P0.30 and P0.31 are mapped to AIN6 and AIN7. 
But I found something in devicetree file nrf52840dk_nrf52840.dts. P0.30 and P0.31 are mapped to AIN6 and AIN7.

I deactivated them but it still doesn't work.

	arduino_adc: analog-connector {
		compatible = "arduino,uno-adc";
		#io-channel-cells = <1>;
		io-channel-map = <0 &adc 1>;	/* A0 = P0.3 = AIN1 */
		/* 		 <1 &adc 2>,	/* A1 = P0.4 = AIN2 */
		/*		 <2 &adc 4>,	/* A2 = P0.28 = AIN4 */
		/*		 <3 &adc 5>,	/* A3 = P0.29 = AIN5 */
		/*       <4 &adc 6>,	/* A4 = P0.30 = AIN6 */
		/*       <5 &adc 7>;	/* A5 = P0.31 = AIN7 */
	};

[Vidar Berg]

The error message comes from the TWIM or TWI driver here: https://github.com/nrfconnect/sdk-zephyr/blob/78a9e8effce0366562b9bb1f4e08096fa4cb13b9/drivers/i2c/i2c_nrfx_twim.c#L171 or here https://github.com/nrfconnect/sdk-zephyr/blob/main/drivers/i2c/i2c_nrfx_twi.c#L126.

Do you have a logic analyzer or scope you can use to check if anything if anything is being transmitted on P0.30 and P0.31 or if both lines are kept low?