Monday, October 24, 2011

Teensy Programming Shield

Jeff - KO7M and I have been working on several Arduino and Teensy projects, to control QRP and Beacon Transmitters. To expand and progress to the point where we will use raw chips in planned projects we decided to produce a Teensy Programming (under) Shield. For several projects we have used the Teensy as the development platform.
As Designed in DipTrace

The Teensy will plug into the top of the Shield. After several iterations and corrections of schematic I we have a layout.

Today, I used the Toner Transfer Method to create the board. High resolution two sided boards are tough but they can be done. The Teensy Programming Shield is .75" x 1.75" with 8 mil traces.

Etched and Ready for Inspection
There are not many traces so it was not hard to route or build. If I had need for more than a few boards I would have sent it out for FAB.

The Etch Looks Good
and both sides look like they are in good alignment
These are 8 mil Traces, and 6 mil Ground Grid
After Laser Toner Resist is remove, the board is cleaned and polished, and then placed into a small dish of Tinnit. In about 5 minutes the board is bright and shiny.
Tinnit was used for Tin Plating
Tinnit works well, with good coverage,
but it is very thin (.004").
The Results:

Parts Loaded
Double sided HB board are difficult as the socket pin are typically used to transfer the traces between sides and therefore both sides of the socket pins require solder. With care this can be done by raising the socket a small amount and soldering with a very sharp iron. Also, small errors of alignment between the image of each side make for difficult drilling and therefore pad are not always centered on the component pins.

Cut, Drilled and Parts are loaded, in this case Headers and one jumper.

Ready to Use !
As you can see the Header were raised about 1/10" to facilitate top side soldering the few pads which are connected via traces. Raising the parts would not be necessary if this board was from a FAB shop, plated through holes would make loading parts much easier.

In use, the Teensy will cover the first 24 pins (far end), short jumpers will be used if need for the none standard Teensy pin locations. For ISP Programming effort, only one jumper will be required - the RST pin.

With the Teensy plugged in hopefully there will be enough space to plug in the programmers? To use the Shield to program the Teensy, a short jumper is still needed between the RST pin (on end of the Teensy) and the third pin on the near open socket holes. That hole, is connected to the RST pin on the 6 pin Programming Header. We could have included dedicated RST pin and socket as part of the Shield, but that would require we alter the Teensy with a dedicated pin, disallowing it to be used directly with simple circuits on protoboards.

The Teensy is Installed, Ready for Programming,
It can be used
In or Out of a Protoboard
Now it is time to do some Direct AVR Programming - Jeff!


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