RE: Do I need pull-up resistors when using I2C or does the driver set them up in software?

Håkon Alseth — Tue, 06 Aug 2024 14:08:03 GMT

Hi,

Glad to hear that you got it working.

To enable internal pull resistors, you need to set this in the device tree node by adding "bias-pull-up;":

&pinctrl {
	new_pinctrl_default: new_pinctrl_default {
		group1 {
			psels = <NRF_PSEL(TWIM_SDA, 0, 26)>,
				<NRF_PSEL(TWIM_SCL, 0, 27)>;
			bias-pull-up;
		};
	};

	new_pinctrl_sleep: new_pinctrl_sleep {
		group1 {
			psels = <NRF_PSEL(TWIM_SDA, 0, 26)>,
				<NRF_PSEL(TWIM_SCL, 0, 27)>;
			low-power-enable;
		};
	};    
};

&i2c0 {
    ...
	pinctrl-0 = <&new_pinctrl_default>;
	pinctrl-1 = <&new_pinctrl_sleep>;
	pinctrl-names = "default", "sleep";
};

Please note that the internal pull resistors are too weak for 400 kHz operation, but will work for 100 kHz i2c transfers.

Kind regards,

Håkon

RE: Do I need pull-up resistors when using I2C or does the driver set them up in software?

olalonde — Tue, 06 Aug 2024 13:59:22 GMT

I used external 5k pull up resistors and it seems to be working now.