I neglected my blog for the past couple of weeks and looking at the stats there seems to be a bit of an interest for Ponte, so I thought I’d quickly talk about the current state of it with a few photos of the prototype.
I present to you: Ponte Revision 0 (with obligatory prototype wire fixes)
A couple of weeks ago I visited Sukkin to have a play with the prototypes, debugging things as we went along. The first bit we’ve tested was the automatic power selection transistor voodoo, which was not working as intended, until….
…Sukkin pointed out that I swapped the drain/source on the FETs. It’s been a while since I’ve played with transistors, so yeah, [insert deity here] bless cheap PCB prototypes!
After a bit of surgery on the board, I’ve put down the rest of the bits and was pleasantly surprised to see that it was all working fine! The next day, I wrote some code to get readings out of the ADC we’ve picked and made sure the I2C level translation was working as well.
Now, for the problematic bits: Mechanically it’s impossible to use this revision of the board sensibly since the connector for the Pi interferes with both the shield that sits on top of it and the USB connector on the Arduino in the other configuration where Ponte sits on top of the Arduino.
Another problem is that the DC jack is quite close to the same connector, so plugging in IDC cables is not possible with the jack soldered in.
Which brings me on to…
With the mechanical bugs squashed by enlarging the size of the board a little bit and leaving more space between the IDC header and the DC jack, we ended up with quite a bit of extra space so I added an 8-bit I2C port expander so that the board didn’t look that empty. The schematic now looks a bit like this:
And the (unrouted) board looks like:
We should be finished with this fairly soon.
As promised, the design files will be released as Open Source Hardware once I am happy with the new revision.
Where can I get one of these?
I’ve had a few emails from enthusiastic folks interested in acquiring one of these boards, but I’m afraid we don’t have any plans to sell assembled units (small scale electronics manufacturing is a painful and time consuming process). We might revisit the idea later, though.
This board is designed as part of a Knowledge Transfer Partnership project between University of Kent and Erlang Solutions, where I explore using the programming language Erlang in the embedded domain. We are using Raspberry Pi as one of our target platforms and this board, when finished, will simplify our explorations. For more information, visit our Erlang Embedded site.