change sda and scl pin for i2c1 on nrf5340

RE: change sda and scl pin for i2c1 on nrf5340

Carl Richard — Tue, 15 Sep 2020 13:27:39 GMT

Hello again!

I miswrote when I said I got it to work with pins P0.02 and P0.02. The DK requires some modifications to support the NFC pins as conventional GPIOs, as described below:

"Pins W1 and AA1 are by default configured to use the NFC antenna, but if they are needed as normal GPIOs, R43 and R46 must be NC and R42 and R45 must be shorted by 0R."

This is described here

Best regards,
Carl Richard

RE: change sda and scl pin for i2c1 on nrf5340

Divya BM — Tue, 15 Sep 2020 12:50:18 GMT

Hi Carl!

You are correct. Everything is the same except for nrf5340pdk_nrf5340_cpuapp.overlay:

&i2c1 {
	status = "ok";
	compatible = "nordic,nrf-twim";
	sda-pin = < 3 >;
	scl-pin = < 2 >;
    clock-frequency = <I2C_BITRATE_STANDARD>; 
};

Regards,

Divya

RE: change sda and scl pin for i2c1 on nrf5340

Carl Richard — Tue, 15 Sep 2020 12:12:29 GMT

Hello, again!

How does your prj.conf look?

The following are my I2C settings, see if yours match.

prj.conf:

# I2C
CONFIG_I2C=y
CONFIG_I2C_NRFX=y
CONFIG_I2C_1=y
CONFIG_NRFX_TWIM1=y

CONFIG_NFCT_PINS_AS_GPIOS=y

nrf5340pdk_nrf5340_cpuapp.overlay:

&i2c1 {
	status = "okay";
	compatible = "nordic,nrf-twim";
	sda-pin = <33>;
	scl-pin = <34>;
	clock-frequency = <I2C_BITRATE_STANDARD>; 
};

main.c (extract):

void main(void)
{
	printk("The I2C test started\n");
    struct device *i2c_dev;
	int error;

    i2c_dev = device_get_binding("I2C_1");
    if (!i2c_dev) {
        printk("Binding failed.");
        return;
    }
    i2c_configure(i2c_dev, I2C_SPEED_SET(I2C_SPEED_STANDARD));
    
//(...) 
}

Best regards,
Carl Richard

RE: change sda and scl pin for i2c1 on nrf5340

Divya BM — Tue, 15 Sep 2020 11:39:17 GMT

Hi Carl!

I added "CONFIG_NFCT_PINS_AS_GPIOS=y" in "prj.conf" and

sda-pin = < 3 >;//P0.3
scl-pin = < 2 >;//P0.2

in "nrf5340pdk_nrf5340_cpuapp.overlay". However, i2c_transfer fails as follows:

" <err> i2c_nrfx_twim: Error 195952641 occurred for message".

Is there any other change required?

Regards,

Divya B M

RE: change sda and scl pin for i2c1 on nrf5340

Carl Richard — Tue, 15 Sep 2020 10:58:38 GMT

Hi again, Divya!

Add the following to your prj.conf:

CONFIG_NFCT_PINS_AS_GPIOS=y

With fairly low I2C frequency it should work fine!

Best regards,
Carl Richard

RE: change sda and scl pin for i2c1 on nrf5340

Divya BM — Tue, 15 Sep 2020 04:36:24 GMT

Hi Carl!,

I see that the NFC pins(P0.02 and P0.03) can also be used as GPIO pins. The documentation states " The pins dedicated to the NFCT antenna function will have some limitation when the pins are configured
for normal GPIO operation". So, there should be a way to use these pins as well for i2c1. Is there any configuartion to set these NFC pins as GPIO pins?

Regards,

Divya B M

RE: change sda and scl pin for i2c1 on nrf5340

Divya BM — Mon, 14 Sep 2020 14:36:38 GMT

ok great! Thanks!

RE: change sda and scl pin for i2c1 on nrf5340

Carl Richard — Mon, 14 Sep 2020 14:34:30 GMT

My apologies. I gave you the wrong pin numbers!

I must ask internally about available pins. Will come back to you tomorrow.

Best regards,
Carl Richard

RE: change sda and scl pin for i2c1 on nrf5340

Divya BM — Mon, 14 Sep 2020 14:23:27 GMT

Hi Carl!

In nrf5340pdk_nrf5340_cpuapp.overlay, changing

sda-pin = < 33 >;
scl-pin = < 34 >;

sda-pin = < 34 >;//P1.2
scl-pin = < 35 >;//P1.3

helped.

Also, since you mentioned

[quote userid="68044" url="~/f/nordic-q-a/65900/change-sda-and-scl-pin-for-i2c1-on-nrf5340/269378"]The pins P0.02 and P0.03 are dedicated to NFC on the DK, so using them could yield erroneous behavior[/quote]

we have a restriction on the number of gpio pins that are free. So, can we use any other GPIO pin with digital i/o as SDA and SCL pin for i2c?

Regards,

Divya

RE: change sda and scl pin for i2c1 on nrf5340

Carl Richard — Mon, 14 Sep 2020 13:54:31 GMT

Hello, Divya!

Could you try to add the following to your prj.conf:

CONFIG_NRFX_TWIM1=y
CONFIG_I2C_NRFX=y

Hope that will work!

Best regards,
Carl Richard

RE: change sda and scl pin for i2c1 on nrf5340

Divya BM — Mon, 14 Sep 2020 13:19:38 GMT

Hi Carl!

Thanks for the quick response.

[quote userid="68044" url="~/f/nordic-q-a/65900/change-sda-and-scl-pin-for-i2c1-on-nrf5340/269378"]You can just add the file nrf5340pdk_nrf5340_cpuapp.overlay in your project directory[/quote]

I tried this. I see that the value reflects correctly in "devicetree_unfixed.h" generated file as follows:
#define DT_N_S_soc_S_peripheral_50000000_S_i2c_9000_P_sda_pin 33
#define DT_N_S_soc_S_peripheral_50000000_S_i2c_9000_P_scl_pin 34

However, when i make the corresponding connections, i2c_transfer fails as follows:

" <err> i2c_nrfx_twim: Error 195952641 occurred for message".

My prj.conf file is:
CONFIG_I2C=y
CONFIG_I2C_1=y
CONFIG_SENSOR=y

Am i missing something else? Any help with this will be useful. Thanks in advance!

Regards,

Divya B M

RE: change sda and scl pin for i2c1 on nrf5340

Carl Richard — Mon, 14 Sep 2020 12:58:22 GMT

Hello, Divya!

The pins P0.02 and P0.03 are dedicated to NFC on the DK, so using them could yield erroneous behavior. According to the nRF5340 documentation pin P1.2 and P1.3 should be suitable for TWI.
I also want to add tht recommend using an overlay when configuring peripherals in NCS. You can just add the file nrf5340pdk_nrf5340_cpuapp.overlay in your project directory, with the following contents:

&i2c1 {
	status = "ok";
	compatible = "nordic,nrf-twim";
	sda-pin = < 33 >;
	scl-pin = < 34 >;
    clock-frequency = <I2C_BITRATE_STANDARD>;  
};

Make sure that Prj.conf is configured correctly aswell.

Let me know if this works for you or not.

Best regards,
Carl Richard