Greg and I have been playing around with ePapers projects and every now and then I get caught out with an issue and have no quick way to see whats happening with the various voltages and signals used to drive an ePaper. We what chatting away about this, we thought that it would be handy to just "see" the signals and after a few rounds of bouncing ideas back and forth this simple board eventuated:
Above the green ePaper signal testboard is placed in series between the controller and the ePaper. A bunch of LEDs have been placed on all the usable pins of the 24 lines that make up the ePaper flex connector. I have used a few zener diodes to limit some of the positive/negative driver voltages. This board works well and if you watch carefully, you can see the LEDs brighten or dim according the generated voltages. You can even see the SPI LEDs flash when data is being sent. The only issue is I labeled the red LED as being able to detect reverse cable being plugged in in reverse. It doesn't work. It kind of shows the opposite.
As part of designing this board, I borrowed Stephens oscilloscope and scoped out each pin and added the screenshots into a public Gitlab repository folder, along with a spreadsheet of notes and KiCAD board design files. Greg designed up a similar version in EasyEDA and that too is in the repo. This will make it easy for anyone to make their own version. Enjoy!
Since I have built the board, I have used it a lot. It's handy to see whats going on (or not) and to easily be able to measure different pin voltages or even to test continuity or shorts at the fine pitch 24 pin flex connector.
You can find the PCB design files and some example o'scope screen shots here: https://gitlab.com/parkview/e-Paper_Test_Board
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