Combine uClinux and Asterisk on a Card

Embedding Asterisk on a Digikey Blackfin STAMP card.

The configuration files for Asterisk are the same as for x86 Asterisk. Some useful files are:

  • /etc/zaptel.conf: Zaptel driver configuration

  • /etc/asterisk/zapata.conf: more Zaptel configuration.

  • /etc/asterisk/extensions.conf: sets up dial plan for PBX.

  • /etc/asterisk/sip.conf: SIP phone configuration.

These files can be edited with vi on the Blackfin, but remember that any configurations will be lost when the board is powered down or reset. Permanent changes can be stored on the SD card.

Further Work

So, there you have the basic steps for building your own embedded Asterisk PBX. Kits containing the daughterboards and modules are available from the author. We are working on further development—for example, custom Blackfin hardware designed specifically for telephony work and other line interface cards, such as BRI-ISDN. It's an exciting project, with the novel feature of open hardware development.

David Rowe has 20 years of experience in the development of DSP-based telephony and sat-com hardware/software. David has a wide mix of skills including software, hardware and project management, and a PhD in DSP theory. He has held executive-level positions in the sat-com industry ( and has built and successfully exited a small business ( However, he has decided he is better at debugging machines than people, so he currently chooses to hack telephony hardware and software full time.



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blackfin dsp and asterisk?

codentest's picture

I didn't think asterisk supported the dsp functions/instructions of blackfin. Which means using blackfin dsp does not help may infact be less efficent as most of the asterisk codec code is geared towards x86 systems.

Embedded open-source telephony

dpgood's picture

Hugely helpful!

I have been looking everywhere for information on putting together an embedded telephony card to use to build an adjunct telephone box. Although the Asterisk section is overkill for me, I need the FXS/FXO piece, and to be able to do pass-through.

I'll check into the resources you posted as well. Thanks for being so complete -

Dana Good

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