How to connect an Accelerometer (byteSENSI-A) to the byteDEVKIT OSM-S

This guide walks through the process of adding the accelerometer BMA400 to the byteDEVKIT OSM-S with the OSM-S iMX93 byteENGINE module. First step is to connect the external hardware component to the byteDEVKIT. Afterwards, the Linux kernel is modified.

The accelerometer BMA400 board has the following pins:

• VDD (1.62-3.6V)

• SCL

• SDA

• I2C_ADDR_SELECT (GND: 0x14, VDDIO: 0x15)

• INT

• GND

Connect the pins with header cables to the 60 Pin Connector on the byteDEVKIT OSM-S.

The datasheet of the byteDEVKIT OSM-S shows the pinout of the 60 Pin Connector (3.6 X12 60PIN Connector). It can be downloaded from the bytesatwork downloads page: https://bytesatwork.io/de/downloads/datasheet-bytedevkit-osm-s-v1.0.pdf

The following table shows how to connect the BMA400 to the byteDEVKIT-OSM-S:

See the relevant schematic parts to connect the two hardware boards with each other:

To be able to build the linux kernel, the correct toolchain needs to be installed. Download and install the toolchain from byteWIKI:
https://bytewiki.readthedocs.io/en/latest/yocto/5.0/bytedevkit-imx93.html

Then clone the linux kernel repository for the iMX93:

git clone -b baw-lf-6.6.52-2.2.0 https://github.com/bytesatwork/linux-imx.git
cd linux-imx

Firstly, the accelerometer is added to the device tree.

Open the device tree file arch/arm64/boot/dts/freescale/imx93-bytedevkit.dts and add the accelerometer in the i2c1 node:

&lpi2c1 {
	#address-cells = <1>;
	#size-cells = <0>;
	clock-frequency = <400000>;
	pinctrl-names = "default", "sleep";
	pinctrl-0 = <&pinctrl_lpi2c1>;
	pinctrl-1 = <&pinctrl_lpi2c1>;
	status = "okay";
	/* LVDS Touch */
	gt911@5d {
		...
	};
	accelerometer@14 {
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_accelerometer>;
		compatible = "bosch,bma400";
		reg = <0x14>;
		interrupt-parent = <&gpio2>;
		interrupts = <9 IRQ_TYPE_LEVEL_HIGH>;
	};
};

Also add the pincontrol for the accelerometer in the iomuxc node:

&iomuxc {
	pinctrl_accelerometer: accelerometer_grp {
		fsl,pins = <
			MX93_PAD_GPIO_IO08__GPIO2_IO08		0x100	/* I2C ADDRESS SEL */
			MX93_PAD_GPIO_IO09__GPIO2_IO09		0x0	/* INT */
		>;
	};
 
   ...
   
};

Next the driver needs to be enabled in the config.

Open the file arch/arm64/configs/bytedevkit_imx93_defconfig and append the following to lines to the end of the file:

CONFIG_BMA400=y
CONFIG_BMA400_I2C=y

Now the kernel image and device tree need to be built:

source /opt/poky-bytesatwork/5.0.5/environment-setup-cortexa55-poky-linux
make bytedevkit_imx93_defconfig
make -j4 Image freescale/imx93-bytedevkit.dtb

Copy the compiled image and device tree to the device. This can be done be writting it directly to the SD card or by copying it with scp to the running byteDEVKIT OSM.

To copy the files over scp, boot the byteDEVKIT OSM and connect the ethernet cable. Run ifconfig to get the IP address of the device. Then copy with scp:

arch/arm64/boot/Image
arch/arm64/boot/dts/freescale/imx93-bytedevkit.dtb

Need to be copied to the /boot/ folder of the byteDEVKIT OSM.

Boot the device with the new kernel. Connect to the device over the UART console.

Check what iio devices exist:

ls /sys/bus/iio/devices/

If multiple devices exist, use the name property to identify which device is the BMA400.

In this example device1 is the accelerometer:

ls /sys/bus/iio/devices/
iio:device0  iio:device1  trigger0
cat /sys/bus/iio/devices/iio:device0/name
imx93-adc
cat /sys/bus/iio/devices/iio:device1/name
bma400

Read the accelerometer measurements:

cat /sys/bus/iio/devices/iio:device1/in_accel_x_raw
cat /sys/bus/iio/devices/iio:device1/in_accel_y_raw
cat /sys/bus/iio/devices/iio:device1/in_accel_z_raw