The latest PCB revision is on it's way to fabrication and there are lots of changes to note.

First, GDEY042T81-FT02 replaces GDEW042T2 as the e-paper and also adds a touchscreen and back-light to the project. The touchscreen removes the need for navigation buttons, but I added two side-actuated buttons to physically control the back-light brightness.

One easy thing to miss about GDEY042T81-FT02 is the touchscreen and back-light ribbon cables are the exact same dimension but reversed pin numbers.

Both ribbon cables are 6 pin, 0.5mm pitch, but from left to right, the back-light pins are 6, 5, 4, 3, 2, 1, but the touchscreen pins from left to right are 1, 2, 3, 4, 5, 6. I'm not sure why it's designed like this. Especially since there are only two signals on the back-light ribbon. Pins 1 and 2 are LED+, pins 3 and 4 are unconnected, and pins 5 and 6 are LED-. Regardless, I made two different footprints with identical geometry but reversed pin-outs to accommodate for this weirdness.

For the carrier board, the SD card in the previous layout was conveniently placed exactly where the touchscreen ribbon cable lays.

I moved the status LEDs and SD card to accommodate for the touchscreen and back-light ribbon cables. Also, without the navigation buttons, the layout width is smaller and I had to move the USB micro connector further away from the computer\ module. The back-light brightness buttons also required shifting the portable power ICs and related components closer to the interior of the board.

Last layout update, I mentioned needing a sea of vias to route traces to the 100 pin Hirose connector. This problem became even worse with the addition of the touchscreen and back-light.

I joked previously about sticking to a 2 layer board to be frugal, but adding any other hardware will almost certainly require that I finally move to a 4 layer board.

Let's hope the this board is functional once it comes back from fabrication. For the most update code and hardware, please visit the project's repository.