Holo: rp probe (the official one) has swclk on gpio 12 and swdio on gpio 14.
If you clone the rp-hal repo, and run the blinky example (but change the led pin to match the above) you should be able to observe the signals going high and low.

https://github.com/rp-rs/rp-hal/blob/e175d2a4865a42f75f84fde4682eae7cc41d8daf/rp2040-hal/examples/blinky.rs#L80
This repo is already set up to use elf2uf2-rs as the runner, so you should be able to mount the drive the load the blinky using

```
cargo run --release --example blinky 
```