zeronote / lx_lis3dh

Simple DTBO and out-of-tree driver module for ST LIS3DH accelerometer.

BBB Pin Mapping Table

BBB P9 header	LIS3DH
Pin 1 (DGND)	GND
Pin 3 (VDD_3V3)	Vin
Pin 15 (GPIO_48)	INT
Pin 19 (I2C2_SCL)	SCL
Pin 20 (I2C2_SDA)	SDA

TOOLCHAIN SETUP

Really important disclaimer

My first really important assumption is that you are working on a Beaglebone Black system with the following:

• U-Boot 2016.01-00001-g4eb802e (Jan 13 2016 - 11:14:31 -0600)
• Linux beaglebone 4.1.15-ti-rt-r43

otherwise, depending on u-boot and kernel version, some of the followings steps could be erroneous or lead to undefined results.

Packages

The following packages are needed if you are on a Debian/Ubuntu based host machine:

• lib32stdc++6
• lzop
• lib32z1
• zlibc
• device-tree-compiler
• build-essential

Pre-setup

To avoid problems during kernel module insmod, replace the Module.symvers_beaglebone in this repo with the one in you kernel headers. E.g.

scp [email protected]:/usr/src/$(uname -r)/Module.symvers Module.symvers_beaglebone

this should prevent errors like:

insmod error: inserting './lxdriver.ko': -1 Invalid module format

which, looking at dmesg, point us to the Module.symvers root cause:

lxdriver.ko: no symbol version for module_layout

Setup

Simply executing setup.sh should download, configure and cross-compile everything for you except the LIS3DH kernel module that you're supposed to cross-compile by yourself using make once the setup.sh script exit. If everything went well, you should have the followings in your current directory:

• lxdriver.ko
• BB-LX-ACCEL-00A0.dtbo

Once gained any kind of access to your BBB, copy the kernel lxdriver.ko in /lib/modules/$(uname -r)and BB-LX-ACCEL-00A0.dtboto /lib/firmware.

Testing

Since the universal_cape overlay is enabled by default, we need to disable it to avoid race conditions on the GPIO_48 pin once our overlay is loaded: with sudo vim /boot/uEnv.txt change this line:

cmdline=coherent_pool=1M quiet cape_universal=enable

to

cmdline=coherent_pool=1M quiet

and reboot your BBB.

Finally we can load the dtb overlay

sudo sh -c 'echo BB-LX-ACCEL-00A0.DTBO > /sys/devices/platform/bone_capemgr/slots'

load the kernel module:

sudo insmod /lib/firmware/lxdriver.ko

and check our 3-axis accelerations:

sudo cat /dev/lxaccell

debian@beaglebone:~$ sudo cat /dev/lxaccell
787,298,540
787,298,540
780,304,541
780,304,541
780,304,541
780,304,541
780,304,541
780,304,541
780,304,541
780,304,541
780,304,541
780,304,541
780,304,541