Attaching an I2C Device to MicroE Click Connector

Owned by Dmitry Konyshev
Last updated: Feb 26, 2024 by Natalia Sofronova
2 min read

This application note describes how to connect an I2C device to the J1 MicroE Click Connector and enabled the device support in the Linux kernel. The DS1339 Real-Time Clock chip is used to demonstrate this capability.

  1. Connect a DS1339 sensor to the J1 MicroE Click Connector as follows:

    • J1B.9 - GND

    • J1B.12 - SCL

    • J1B.13 - SDA

    • J1A.7 - VCC

  2. Boot the board and check that an I2C device (0x68) is found on Bus I2C2:

    / # i2cdetect -y 2 0 1 2 3 4 5 6 7 8 9 a b c d e f 00: -- -- -- -- -- -- -- -- -- -- -- -- -- 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- -- 70: -- -- -- -- -- -- -- --

  3. Check out the STM32MP1 kernel source code as described in Application Note Building Linux Kernel.

  4. Add a device node description for the DS1339 sensor to the I2C2 node of the device tree (arch/arm/boot/dts/stm32mp157x-bsb.dtsi):

    &i2c2 { pinctrl-names = "default", "sleep"; pinctrl-0 = <&i2c2_pins_a>; pinctrl-1 = <&i2c2_sleep_pins_a>; i2c-scl-rising-time-ns = <185>; i2c-scl-falling-time-ns = <20>; /delete-property/dmas; /delete-property/dma-names; status = "okay"; clock-frequency = <1000000>; ds1339: rtc@68 { compatible = "dallas,ds1339"; reg = <0x68>; trickle-resistor-ohms = <250>; trickle-diode-disable; }; };

  5. Rebuild and update the kernel on the board.

  6. The DS1339 Real-Time Clock chip should be visible as the /dev/rtc1 device in the system.