2021-01-28 Update

A project log for BlueRetro

Multiplayer Bluetooth controllers adapter for retro video game consoles

Jacques GagnonJacques Gagnon 01/28/2021 at 13:110 Comments

Already a month in the new year!

No new release yet but I figured I'll make a quick update since I feel I still got some weeks of work ahead before anything new.

One of the biggest challenge doing BlueRetro is systems protocols that requires to use software bit-bang. In a chip as complex as the ESP32 running FreeRTOS on two cores you don't control what the CPUs are doing as much as with a PIC or an AVR micro. If you loose the CPU while TX or RX bit bang your data is now corrupted.

So in this context its always better to try to use one of the HW peripheral and abuse them to talk a non-standard protocols. For example the N64 & GC driver use the RMT hardware (for IR remote) to implement Nintendo's 1-wire protocols in a very robust way. But its not always possible to do so, so its important to be able to bit-bang reliably.

I've been experimenting for the better part of the month on trying to restrict FreeRTOS on a single core and run the 2nd one bare metal base on the work of @Daniel with #Bare metal second core on ESP32 . Results are promising so far, I made a small demo here:

The big challenge in doing so is that the core can't touch the flash anymore and all instructions and data need to be in RAM. I got the PSX driver working which is one of the more complex one with its 3 interrupts. I still got a lot of rework to do to get everything working with that design but it's really worth it as it will end my fight with the GPIOs and make the bit-bang interfaces 100% reliable.