Writing assembly for the ESP32 S3 is fun, don't get me wrong. But it is also very frustrating when you have to debug it, rebuild, wait for the upload, monitor, crash, repeat. I know you can do emulation and gdb, but to be fair, I haven't ever used gdb before and I don't feel like learning to use it at this time.

At the same time, I'm still learning all the ins and outs of the instructions available on the Xtensa CPU. This basically boils down to reading and rereading the ISA over and over until it sticks. 

I'm all for getting things done fast, with the least amount of resources spent, because I'm a prototyper making proof-of-concepts. But you do have to be smart about it. I noticed that as my program grows in complexity, so does the time debugging the assembly and its overhead (building, flashing).

So I decided to spend a considerable amount of time writing an ESP32 S3 emulator, in python. It must be able to read some assembly, execute it and be able to show me the state of the registers. I can then import this in a notebook and start an interactive session with the emulator basically. When the assembly does what it is supposed to do, it could output the assembly to be assembled by the assembler, or maybe even assemble it itself.

This will give me 2 things:

• I will learn the details of every instruction in the ISA and get a very detailed overview of the CPU's inner workings.
• I can develop and debug much quicker

My prediction is that the time spent writing this emulator is very easy to win back, considering the amount of assembly code I want to write for this (and subsequent) projects.

The code will be available here. Keep in mind that its purpose is to serve the 2 goals stated above, not to be a complete or perfect emulator.

esp32s3_emu on github