I'm upset that there is no good way to multiplex SWD connections across multiple devices. This makes building and testing an assembly of say... 4 to 8 devices needlessly painful.
I want JTAG scan chains, damn it, and I have a feeling I'm just going to write a bootloader instead.
Conversation
I guess ANOTHER bootloader, since I already wrote sprocket-boot.
1
2
My last solution with anachro was to just have four cheap SWD debuggers attached to a USB hub, which... worked, but did not bring joy.
I feel like I'm going to do it again though, sadly.
1
1
Replying to
My solution up to this point has been a collection of gdbstub bootloaders over USB tied into Erlang system for orchestration. Next iteration is modded black magic probe firmware on blue pill boards. That also runs on those STLink clone boards BTW.
1
1
Replying to
Interesting! This project is specifically a bus with a network, so I've been musing on/avoiding building logging and bootloading capabilities into the bus itself. I do have a stock of black-pill (stm32f4) boards, which I could use as debuggers in a pinch.
1
Replying to
I have proof of concept logging working over SWD. Basically BMP firmware is modded so it polls the uC's log buffer while polling for target halt due to breakpoint. At this point I'm not quite sure if the multiplex is a good idea. First iteration is probably simpler to ...
1
... have multiple boards, one SWD interface per uC, and solve the orchestration on some debug PC. I'm trying to make a case to add some compile time hooks to BMP firmware so it can run "apps" but up to now I've just confused people: github.com/blacksphere/bl ...
Replying to
Nice! Your logging scheme sounds very similar to Segger's RTT protocol, which is also pretty much what probe.rs (and most of the Rust ecosystem) uses (though not specific to Segger's HW).
It basically keeps a ring buffer in RAM, the MCU pushes, and dbg pops.
1
Replying to
Yes. I there is a BMP patch for that I believe. But ppl are a bit scared to integrate due to patent issues. Not sure it's been a couple of months since I looked at this.
1
Show replies
... idea is to do arbitrary messages over SWD. Basically make a dedicated debug/test system that is specific for one application. I hope to finish this as part of my current client project but unclear about timeline. I have a bag of STLinkV2 clones ready!
1
1
Replying to
In general, the probe.rs project has taken a different approach: use off-the-shelf debuggers (STLink, JLink, CMSIS-DAP, etc.), and instead make a host-side library that gives you pretty deep control.
It's how we do a TON of the tooling for embedded rust.
1
Show replies