I have extracted the NTSC color composite video generation code from rossumur's ESP_8_BIT project, and tested it by showing a static image. The obvious next step is to put something on screen that moves, and my test case is Adafruit's Uncanny Eyes sketch. This is a nifty little display I encountered on Adafruit's Hallowing and used in a few projects since. But even though I've taken a peek at the code, I've yet to try running that code on a different piece of hardware as I'm doing now.

Originally written for a Teensy 3 and a particular display, Uncanny Eyes has grown to support more microcontrollers and display modules including those on the Hallowing. It is now quite a complicated beast, littered with #ifdef sections blocking out code to support one component or another. It shows all the evidence of a project that has grown too unwieldy to easily evolve, which is probably why Adafruit has split into separate repositories for more advanced versions. There's one for Cortex-M4, another one for Raspberry Pi, and possibly others I haven't seen. In classic and admirable Adafruit fashion, all of these have corresponding detailed guides. Here's the page for the Cortex-M4 eyes, here's the page for Pi Eyes, in addition to the Teensy/Hallowing M0 eyes that got me started on this path.

If my intent was to put together the best version I can on a TV, I would study all three variants. Read Adafruit documentation and review the code. But my intent is a quick proof of concept, so I pulled down the M0 version I was already familiar with from earlier study and started merrily hacking away. My objective was putting a moving eye on screen, and the key drawEye() method was easily adapted to write directly to my _lines frame buffer. This allowed me to cut out all code talking to a screen over SPI and such. This code had provisions for external interactivity such a joystick for controlling gaze direction, a button for blink, and a light sensor to adjust iris. I wanted a standalone demo and didn't care about that, and thankfully the code had provisions for a standalone demo. All I had to do was make sure a few things were #define (or not #define)-ed. That left a few places that were inconvenient to configure purely from #define, so I deleted them entirely for the purpose of the demo. They'll have to be fixed before interactivity can be restored in this code.

https://twitter.com/Regorlas/status/1384551877635809282

The code changes I had to make to enable this proof of concept is visible in this GitHub commit. It successfully put a moving eye on my tube TV on my ESP32 using a composite video cable, running the color NTSC composite video generation code I pulled out of rossumur's ESP_8_BIT project. With the concept proven, I don't intend to polish or refine it. This was just a crude test run to see if these two pieces would work together. I set this project aside and moved on to other lessons I wanted to learn.

[Code for this project is publicly available on GitHub]