Carambola i2c IO board with relays – V1.1

I’ve been working on a new version of my Carambola IO board.  I’ve added an interrupt line from the MCP23017 back to the Carambola to allow for a trigger when an input changes (save on having to poll the MCP23017 to check for changes!).

One other small change was the addition of a decouple cap close to the pin headers for the Carambola module.  It helps to keep the +5V in order, on the first version there was a lot on noise on the 5V line. You can get the new schematic here: Carambola IO Board

I re-generated the artwork, broke out the light box and development kit and got to work “spinning” a new PCB.  I’m happy with my timings for exposure and development now and seem to have a repeatable process in place.

Carambola IO board - main components placed

Carambola IO board – main components placed

The double sided PCB above took about 2 hours from PC screen to etched PCB (not drilled!). Got a good clean PCB with well defined tracks.

Carambola IO board - close up of I2C extender

Carambola IO board – close up of I2C extender

Getting the new Carambola module configured was easy.  Once connected to the network I could simple copy my Lua MQTT code from my original board over SSH.

Carambola IO board - ready for testing

Carambola IO board – ready for testing

Now I have to write some more Lua code to handle the interrupt pin and post the changes on the inputs via MQTT!

pcDuino and I2C IO board

Thought I do a quick test with my pcDuino and see if I could get the I2C relay board connected and working on it.

The pcDuino is really easy to get up and running on.. Like the Carambola it can be handy to have a FTDI cable handy to get console access.  Once the serial cable is connected you can configure the network and generally get the board set up for connection to your network.  Sparkfun have a really handy tutorial with the pin-outs, etc.

Getting Ubuntu up and running is easy, and because the pcDuino has on board flash memory, there is no need for a SD card.. kinna cool.

Connecting the I2C IO board requires 3 wires from the pcDuino, no drama, simple!

pcDuino and I2C IO boardAfter I install the i2c tools, I was able to drive the relays and monitor the inputs no problem.

pcDuino and I2C IO board from end

pcDuino on it’s way….

Much excitement here at the moment, my new pcDuino is on it’s way from EXP-TECH in Germany (very cool site BTW!).

pcDuino product picture

pcDuino product picture

Here is a short description from the pcDuino site..

pcDuino is a mini PC platform that runs PC like OS such as Ubuntu and Android ICS. It outputs screen to HDMI. Moreover, it has hardware headers interface compatible with Arduino.

Looks like it might be what I hoped the APC SBC would have been!


VIA Technologies getting into the low cost SBC market.. Heard about this a little while ago, but the exciting thing is Radionics are showing stock! I still have a Raspberry Pi on back order with them.  Supply chains.. nuf said!

VIA’s answer to the Raspberry Pi / BeagleBone

One “problem” is it comes flashed with Android and there’s no news yet as to whether VIA will be opening up the bootloader to allow other operating systems to run on the device.. Only a matter of time I guess. The other is it’s lack of GPIO pins, the only thing I can find on the headers might be an SPI bus (look at J3 in this APC pinout PDF).

On the good side: we have a VGA and HDMI connector.

For €50 + VAT… It would be rude not to get one!