Installation ============ This explains how to install the keyboard switcher onto a BeagleBone Black. Installation should be possible on other platforms with only small changes. Step 1: (Optional) Secure the BeagleBone Follow the instructions at http://hacks.pmf.io/2015/06/21/securing-the-beaglebone-black/ Step 2: Upgrade to at least Linux 4.0.0 Later versions should work as well, but 4.0.0 is fully tested. Download the deb package from here: https://rcn-ee.net/deb/wheezy-armhf/v4.0.0-bone0/ And install. This is required due to the dependency on the f_hid usb device function module. Step 3: Prevent the g_multi module from loading As of June 2015, the stock Beaglebone image uses this module to provide services on the USB device port. We need to disable it because it conflicts with our usage of the device port. In the file: /etc/modprobe.d/local.conf Add the line: install g_multi /bin/true Step 4: Install dependencies # apt-get install libudev-dev # apt-get install libusb-dev Step 5: Activate the second serial port The stock BeagleBone image available as of June 2015 has one serial port activated. This is /dev/ttyO0 and it is used to access the serial console using the dedicated connector on the board. In order to interface with the teensy, a second serial port is required. Normally this would just be a matter of loading the correct device tree overlay. Unfortunately, overlays are not supported in Linux 4.0.0 so a change to the master device tree is required to add /dev/ttyO1. a) Backup the device tree # cp /boot/dtbs/4.0.0-bone0/am335x-boneblack.dtb /boot/dtbs/4.0.0-bone0/am335x-boneblack.dtb.bak b) Uncompile the master device tree file # dtc -I dtb /boot/dtbs/4.0.0-bone0/am335x-boneblack.dtb -O dts -o /tmp/am335x-boneblack.dts c) Apply the patch # patch /tmp/am335x-boneblack.dts <device_tree/activate_ttyO1.diff d) Compile the modified device tree # dtc -I dts /tmp/am335x-boneblack.dts -O dtb -o /boot/dtbs/4.0.0-bone0/am335x-boneblack.dtb e) Reboot and check for the new serial port in /dev # reboot # ls /dev/ttyO1 Step 6: Flash the teensy # cd teensy/loader # make # cd ../firmware # make Connect teensy, press button to enter bootloader # ./upload Step 7: Connect the teensy WARNING: A 3.3V CONVERSION IS REQUIRED ON THE TEENSY OR THE BEAGLEBONE WILL BE DAMAGED. https://www.pjrc.com/teensy/3volt.html 3 wires are required: P9_26 rx|-----------|tx D3 BBB P9_24 tx|-----------|rx D2 Teensy P9_1 gnd|-----------|gnd 3.3V conversion required! Step 8: Setup the cron job In root's crontab, add the line (adjust for location of executable): # crontab -e @reboot /root/usbkbctrl/run_kb