Investigate `DapperMime` alternative `rust-dap`

[SupImDos]

Currently, the project skeleton recommends the usage of DapperMime to transform a Raspberry Pi Pico into a CMSIS-DAP debug probe.

According to a comment thread in the embassy chat, a faster alternative rust-dap exists:

9names
dapper-mime works, but rust-dap is faster as it supports cmsis-dap v2 and uses the rp2040 PIO to drive SWD. here's a build of that to test on, if you're interested
https://raw.githubusercontent.com/9names/binary-bits/main/rust-dap-pico-ramexec-setclock.uf2

Peter Hansen
Always happy to upgrade things! :-) And that's awesome that someone put PIO to use for this.
Is that build based on https://github.com/ciniml/rust-dap ? (Just checking, 'cause that one says it's no faster than other probe implementations, and doesn't mention v2 at least on the readme.)

9names
it is a build of that, yes the readme is out of date
i did some performance profiling earlier this year. cmsis-dap v1 firmwares cap out at around 22KB/sec, cmsis-dap v2 + bit-banging at around 54KB/sec, and cmsis-dap v2 + PIO at about 116KB/sec - we're getting capped by USB FS throughput at that speed unfortunately.
if we had USB HS on rp2040 I assume we would be getting 3-4 times that, which would put us at HS-probe levels of performance

The rust-dap firmware should be investigated, and if it proves to be better than DapperMime then it should replace it in this repository.