BlipBox multipurpose controller

I've just received the first PCB's from BatchPCB for the BlipBox project, very exciting!

The BlipBox is not exactly a 'duino, but uses the standard bootloader and is programmed using the Arduino environment.

The box is a touch screen and LED display unit, in short. The idea is to create an open hardware and software platform for people who like to experiment with this type of device. Open source, of course.

In the near future there will be better diy instructions available, in the meantime I would love your feedback on schematic and pcb design.

Photos and details on the blog: http://blipbox.wordpress.com/

So while I'm waiting for some sockets for the LED matrix, I've connected an LED to verify that the circuit works.

What I'm seeing though is very noticeable flickering. On my vero-board prototype I've never seen this problem, the light is always solid and steady.

The LED cathode connects to a TLC5940, anode to one of five AtMega pins used to multiplex the TLC - full schematic is available on the blog.

The obvious culprit would seem to be the multiplexing. However it works just fine on both breadboard and veroboard with an Arduino. And the firmware is identical.

Is it possible that I've made a mistake with the caps? I've got C1, C2, C3 at 100nF, C4 100uF, C5 unused. R1 is a 5kOhm trimpot set at around 2K7, R2 10K, R3 unused.

Hi, it's very interesting your project. I saw your schematic and i have some doubts.

The tlc5940 will control the rows of the two matrix? What will connect to JP1,JP2,JP3?

Thanks!

And cheers for checking the schematic. What are your doubts?

JP1 is the serial comms interface, plugs into e.g. this FTDI cable.

JP2 is for peripherals such as switches and knobs, which don’t form part of the main board. It provides access to one analog and one digital pin from the AtMega, plus an extra pull-down resistor and cap if wanted.

JP3 is just an alternative pinout for the touch controller. You can use either the smd FFC connector or this to connect the touch screen.

Since my last post I’ve connected the two LED matrices and they work just fine! I’m not sure why it was flickering (badly) when I only had one LED from the matrix connected.

what are the touch controller that you use?

It’s good that all it’s working fine now :smiley:

Yeah cheers - I thought I'd done something silly and buggered the board!

The touch screen I got is made by Higgstec, 5.4". I reckon any 5-wire resistive touch screen will be fully compatible. As for the pin order, that can be configured in the software.