Thursday, January 31, 2013

Easy Pogo Pin Test Jigs

Tindie update: I have a few of the older Rev 0.2 eeZee Propeller breakout boards on clearance at Tindie, $16 each. Also, 10% off eeZee Tiny, 8-pin ATtiny breakout board (coupon code 52CAF8E)

All the Rev 0.3 eeZee Propellers ordered during the Tindie Fundraiser have been shipped after extensive testing.  My test jigs are primitive, but are huge time-savers. One jig programs the board. Another tests VGA. A third tests output pins.

The two pogo-pin jigs are populated on one pair of Radio Shack perfboards #276-158B stacked with 1/4" spacers and #6 hardware I had laying around. 

I had to ream out the holes on top and bottom to fit 1mm pogo pins I got from a seller on AliExpress. The pins are soldered top and bottom.

The FTDI jig is used to program the boards with self-test Spin programs. 

The first test checks every pin to ensure it isn't connected to any other, or to ground or Vcc. This will uncover solder bridges and board defects. It uses the FTDI jig to output test results. The second test checks continuity between pin header pads and MCU pins and makes use of my high precision pin testing jig as well as the FTDI serial output jig.

The above jig electrically connects P0 to P1-P15 and the self-test checks each of these pins to make sure there's output generated. I then do the same for P16 connecting to P17-P27. P28 and P29 are used for EEPROM and P30 and P31 are used for programming. These are tested when programming the board's EEPROM.

The final test, which I ran on a couple of boards just to verify the design, was to run VGA output on each of the four sets of VGA pins on the Propeller and verify that the display looked good. I used my VGA protoboard and connected it to a row of 8 pogo pins. 

First I program the Propeller to use, for example, P0-P7 and place it on the pogo pins for testing. Then I switch the code to use P8-P15, and so on. In every case I got a nice clear VGA display.

At some point I might look at building a more sophisticated test jig with custom PCB but for now this approach works and was simple to get going.

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