pico-extras VS picodvi

In the Pico Extras repository, find the external/pico_extras_import.cmake file

[2] https://github.com/raspberrypi/pico-extras/tree/master/src/c...

pico-extras

There is https://github.com/raspberrypi/pico-extras/tree/master/src/rp2_common/pico_sd_card which is SDIO based, and works for reading/writing sectors, but very bare bones prototype atm.

I've just been getting to grips with the PIO, they are a lot of fun to program. Whilst the instruction set is very limited with only enough memory for 32 of them you can do some pretty sophisticated things. A key part of the flexibility is the ability to execute incoming data as instructions. You can stream in a mixture of data and instructions via the DMA, the PIO separates the two and uses the instructions to modify execution so a simple loop becomes a lot more flexible. You can easily sync several of them up to. The scanvideo library: https://github.com/raspberrypi/pico-extras/blob/master/src/c... which is for producing video signals (like VGA) on the fly with scanlines supplied by the CPU is a good example of what's possible. You can have multiple scanline PIO running at once, each decoding a compressed RLE format including transparency and it composes them all together on the fly.

If you've ever played one of the Zachtronics games (in particular Shenzhen IO) it feels like the programming in one of those games. Tight constraints but major possibilities when you think about it for a while.

The RP2040 is a great MCU for playing with graphics as it can bit bang VGA and DVI/HDMI. There's some info on the DVI here: https://github.com/Wren6991/PicoDVI

I wrote a couple of articles on how to do bit banged VGA on the RP2040 from scratch: https://gregchadwick.co.uk/blog/playing-with-the-pico-pt5/ and https://gregchadwick.co.uk/blog/playing-with-the-pico-pt6/ plus an intro to PIO https://gregchadwick.co.uk/blog/playing-with-the-pico-pt4/

A few years back someone was bit banging DVI and 720p 30fps video straight off the RP2040 GPIO pins with just inline resistors between not and the HDMI cable.

https://github.com/Wren6991/PicoDVI

I have the Adafruit DVI board and have been hacking on it some. It's more fun than should be allowed.

There's a project to get this running using Rust[1]. Currently it outputs the blue channel with sync, but has trouble with the other two channels. I don't have a hardware lab with scope, logic analyzer, etc., so it's not easy for me to debug.

In the meantime, I've been doing some experiments in the C codebase as well[2], mostly in the direction of proportionally spaced bitmap text, using the fonts in the X11 distribution.

[1]: https://github.com/DusterTheFirst/pico-dvi-rs

[2]: https://github.com/Wren6991/PicoDVI/pull/48

There is even bit-banged DVI library for pico.

Apparently, there is a digital video output project for the RP2040 already out there [0]! As for why digital video is more rare, it is because the common digital video formats are higher bandwidth and require higher signal integrity.

[0] https://github.com/Wren6991/PicoDVI

I've seen people implement DVI with PIO, and I'm sure basic missile commands wouldn't be as bandwidth-intensive as that.

For example this guy (https://github.com/Wren6991/PicoDVI) essentially 'bit bangs' CML. Sure its not a completely compliant implementation, but it's pretty close... In his case using a push pull with 3.3V/0V. I don't know how he's getting a 0.8V swing.