Speaker David Rowe
Time 2008-01-30 13:30
Conference LCA2008


Open Hardware

Open Hardware hacking

Free telephony project

open telephony hardware designs

improve the world a little bit

designs can be copied, modified, re-used without restriction

encourage cloning of our products

trend: shifting functionality from hardware to software; this means total system costs are constantly dropping for given amount of functionality.

falling hardware costs are a good thing, especially the developing world.

hardware costs dropping towards 0.

People will copy design and compete with each other, driving prices down.

somebody else does the manufacturing, no need to worry about it ourselves

work well with the Chinese

Why free telephony?

phone call should be a human right, not a privilege

drive costs to $0

Why embedded asterisk?

  • small size
  • low power (3W)
  • no moving parts - no fans or hard disks
  • quiet
  • reliable
  • low cost ($100-$150)
  • cool idea


PABX - Australian term PBX - overseas term

  • FOSS
  • VOIP - massive growth
  • Primary sponsor is Digium, but has many other contributors.
  • alternative forks available


Analog phone standard, 48V to ring phone.

PCI card to interface between PCI bus and telephone line.

Echo cancellation and speech compression require CPU power.

Blackfin processor

  • DSP processor
  • run uClinux
  • low cost ($5-15)
  • integer processor
  • simply design, breaks two processor + DSP paradigm.

Redundant parts removed.

Hardware DSP is just software run on a dedicated processor.

Complicated development environment:

  • Cross compiler and tools
  • Customized kernel and applications

Steep learning curve


Business potential in a $200 IP-PBX with multiple ports.

If value goes out of hardware in business model, it will go elsewhere.

I like building stuff & trying to improve the world.

Open software like Linux and Asterisk have been great things.

Open hardware

We distribute the CAD files and and prototypes.

Need a factory or a day with a soldering iron to build one.

Low bug count, many eyes checking for bugs.

Fuller functional PBX setup within 2-3 weeks.

CVS/SVN for version control of designs (text based).

Re-using hardware building blocks, just glue them together, just like software.

Help each other get strange parts, internationally.

I use a blog, instead of a log book.

Chat to debug hardware problems. Software techniques used to debug hardware issues across the globe.

Normal hardware cost is 70% overhead.

Local factory can manufacturer and customize design without paying international country lots of money.

Design process

  1. Design schematics (gschem)
  2. Design PCBs (PCB)
  3. Assemble prototype
  4. Debug hardware
  5. Port asterisk
  6. etc

FOSS tools, several years behind closed source tools.

Hardware hacking is getting easier

Order obscure parts from websites.

Prototype PCB costs are dropping, was $500, then $3 (in China).


Less then $500 to get all the parts needed to assemble a PCB yourself.

Feel free to email me to get help on getting started.

Help from online communities.

Females are better at SMC soldering then males.

Open hardware IP-PBX Products

  • IP04 - 4 port analog IP-PBX (production)
  • IP08 - 8 port analog IP-PBX (prototype)
  • E1/T1 PRI-Appliance (prototype) - 32 channels - 400 euros.
  • BRI-Appliance (prototype) - 2*4 = 8 channels

Need compliance testing, one off cost, approx $10K. Ensure no excessive interference, will cope properly with lightning strike, etc.


For software developers, potential for very low costs ($100).

similar products $2,000

GUI, callerid a bit unstable at the moment.

Copied FXO FXS card design from manual for chip. Digium also did the same thing.


PCB Fabrication: best place - china

Jaycar, interested in an approved kit?

RAM footprint? Asterisk. 64Meg RAM, Asterisk 13Meg. No special optimisations in Asterisk, need to fix that one day.

Asterisk 1.6beta works. 30Meg memory used for everything.

Spreadsheet in SVN with breakdown of parts cost.

Development board for blackfin exists.

3 distros available for running Asterisk on blackfin.