Hardware 2FA TOTP authenticator

After I decided what screen to use I made a PCB that has a USB port and a place to connect the screen. 

Test with the ST7735 display on the PCB (not the 135x240 ST7789)

Testing the USB HID Keyboard functionality

As I would like to carry the authenticator around I wanted to make it have the same formfactor as a USB flash drive. On aliexpress I found some small screens that looked like they would fit my description:

* SSD1351

* SEPS525

* 80x160 ST7735

* 135x240 ST7789

* 40x160 GC9D01

* 172x320 ST7789

When I received the displays, I dropped some of them straight away. The SEPS525 and SSD1351 were to wide for my application and the 80x160 ST7735 and 40x160 GC9D01 were too small for my liking.

This left me with the 172x320 ST7789 and 240x135 ST7789. In the end I decided on the 240x135 ST7789. This screen is slightly larger than a USB A port, has quite a high resolution and pinout matched the previous screen I was using (the 80x160 ST7735). 

When I started this project I first made several prototypes to test all the features of the LPC1756. The first prototype was to make sure I could power up the LPC1756 and connect using JTAG and SWD.

After the first basic prototype I made a small dev board that breaks out all the pins. (I had a issue where I forgot the pull up on the USB D+ line and the IO pads could be pulled from the dev board quite easily)

The third prototype fixed the USB issue and added via's to all the IO pads