Friday, February 6, 2015

BLED112 on BeagleBone

In the previous post I demonstrated, how a Bluetooth Low Energy dongle can be used to connect a PC and an Android device. While this is sort of project is appealing, connecting PCs and smartphones is not such an interesting use case. It is much more interesting, however, to transfer the PC-side program directly to an embedded device and that's what I will demonstrate in this post.

The Android application used in this post did not change, you can download it here. The BLE server application was updated according to the embedded platform's requirement, you can download the new version here.

There are two baskets of embedded platforms out there. One of them is optimized for low power consumption. They are too limited to run a full-scale operating system therefore their system is often proprietary. Arduino (of which we have seen the RFDuino variant) is one of them but there are many more, e.g. Bluegiga modules also have a proprietary application model. We can typically expect power consumption in the 1-10 mA range with some platforms offering even lower standby consumption.

The other basket contains scaled-down computers and they are able to run stripped down versions of a real operating system. Their power consumption is in the 100-500 mA range and they often sport 100s of megabytes of RAM and gigabytes of flash memory. They are of course not comparable to low power platforms when it comes to power consumption but their much higher performance (which can be relevant for computation-intensive tasks) and compatibility with mainstream operating systems make them very attractive for certain tasks. The card I chose is BeagleBoard Black and my main motivation was that Ubuntu chose this card as a reference platform for its Ubuntu Core variant.

The point I try to make in this post is how easy it is to port an application developed for desktop PC to these embedded computers. Therefore let's just port the BLE server part of the CTS example demo to BeagleBone Black.

There are a handful of operating systems available for this card. I chose Snappy Ubuntu - well, because my own desktop is Ubuntu. Grab an SD card and prepare a Snappy Ubuntu boot media according to this description. It worked for me out of the box. You can also start with this video - it is really that easy. Once you hooked up the card with your PC, let's prepare the development environment.

First fetch the ARM cross-compiler with this command (assuming you are on Ubuntu or Debian):

sudo apt-get install gcc-arm-linux-gnueabihf

Then install snappy developer tools according to this guide.

Then unpack the BLE server application into a directory and set up these environment variables.

export CROSS_COMPILE=arm-linux-gnueabihf-; export ARCH=arm

Enter the beagle_conn_example directory that you unpacked from the ZIP package and execute:

make

This should re-generate cts_1.0.0_all.snap which is already present in the ZIP archive in case you run into problems with building the app. The snap is the new package format for snappy. Then you can install this package on the card.

snappy-remote --url=ssh://192.168.1.123 install ./cts_1.0.0_all.snap

You have to update the IP address according to what your card obtained on your network. The upload tool will prompt you for username/password, it is ubuntu/ubuntu by default.

Update the GATT tree in the BLED112 firmware as described in the previous post. Plug the BLED112 dongle into the BeagleBoard's USB port. Then open a command prompt on the BeagleBoard either using the serial debug interface or by connecting to the instance with ssh and execute the following command:

sudo /apps/cts.sideload/1.0.0/bin/cts /dev/ttyACM0

The familiar console messages appear and you can connect with the Android app as depicted in the image below.


One thing you can notice here is that Snappy's shiny new package system is not ready yet. In order for this package to access the /dev/ttyACM0 device (to which the BLED112 is mapped without problem), it has to run as root. This is something that the Snappy team is yet to figure out. The experience, however, is smooth enough that application development can be started now.



1 comment:

Used PC said...

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