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A dynamic data encoder for embedded systems

john — Sat, 03 Apr 2010 15:41:26 +0000

I personally view Scheme as a good extension language. Something that can be embedded into C code to ease the pain of doing everything in C. I am interested in exploiting this concept on embedded systems where there is a lot of fooling about to make a binary. I still intend to produce binaries and reuse the large amount of existing C code out there. However, I want to script the network communication and in particular the structure of the network packets. I have periodically been working on a tool that attempts to support this. This summer I intend to get rid of the old C code in this project and rewrite it entirely in Scheme apart from the low-level encoder/decoder which will remain in C. In this white paper I attempt to describe the work.

Scripting with Guile on Openmoko

john — Sat, 05 Dec 2009 12:56:41 +0000

Having Guile running on an embedded device is very powerful. You can add scripting capabilities to a C program and avoid some of the cross compilation -> deploy cycles by simply editing the script to change some functionality. As an example I have taken the code from the excellent introductory article Scripting with Guile. I packaged the code so that if you install the tarball or the ipk it will install both the binary and script to a suitable place.

Tarball: http://zedstar.org/tarballs/square-0.1.tar.gz

ipk: http://zedstar.org/ipk/square_0.1-r0_armv4t.ipk

After installing Guile do:

root@om-gta02 ~/ipks $ opkg install square_0.1-r0_armv4t.ipk Installing square (0.1-r0) to root... Configuring square root@om-gta02 ~/ipks $ square result of square is 49 result of square2 is 81

Guile on an Openmoko Freerunner

john — Fri, 04 Dec 2009 10:09:54 +0000

I recently got hold of a bunch of Openmoko Freerunners. I needed a distribution which installs to Flash (NAND) so I chose SHR.

I am very impressed how things have progressed especially in terms of being a phone!

Anyway, this gave me a chance to try out some Guile packages I built. If you have a recent version of SHR unstable the following should work:

http://zedstar.org/guile/

Happy Scheming!

Groking Guile’s FFI

john — Sun, 09 Nov 2008 15:38:49 +0000

I have lately been very busy with work, life and the universe and subsequently have done little hacking. I have recently been examining Guile. Guile has been part of OpenEmbedded for a while so should be easy to get running on numerous embedded devices. Chicken was very recently added to OpenEmbedded, however, lacks support for building eggs in this environment. One thing I really love about Chicken is its very easy to use foreign function interface (FFI). After spending the odd hour over various weekends I have finally begun to grok Guile’s FFI. I plan to build packedobjects for Guile and possibility extend its features.

I really like the idea of extension languages ever since I did some work with Tcl a number of years ago. A great example application was Eggdrop the IRC bot. Lots of kids at the time would program their eggdrop bots using the simple Tcl interface. I think a lot can be said about this approach in terms of learning/teaching programming. I hope to explore this further with my education hat on.