Allow printing defmt output to the RTT console

[xoviat]

defmt is widely used as a logger in the rust embedded ecosystem. This allows seamlessly debugging a rust program while printing defmt output at the same time.

[xoviat]

Oh, and defmt-print must be installed for this to work. Maybe add a tooltip for that?

[xoviat]

@haneefdm Do you have questions about this?

[haneefdm]

Thank you for the PR and I agree it will be very useful for Rust developers Before I look at it, I have a request. I need an example project available on github for me to begin looking at it.

It will be my test case as well. Your github example project should be ready to run with minimal effort on my part (preferably on a Mac). I cannot accept what I cannot test. I am not Rust-educated either.

I you can also update the source code to add a reference to the example github then that would be nice.

Sorry, it took me a long time to get to it. Personal health reasons.

[haneefdm]

Why?

[HaoboGu]

@haneefdm I checked the source of defmt and probe-rs. This is because by default, defmt's message is compressed. The detailed info is stored in .elf file, that's why the executable is needed: without .elf, the message cannot be parsed.

See https://github.com/knurling-rs/defmt/blob/main/decoder/src/lib.rs#L157 . The Table is what's stored in .elf file

[haneefdm]

I lied. I did a cursory review. I don't know what is going on with the executable in the RTTConfigureEvent.

And, then in the constructor of the DefmtSocketRTTSource, you are trying to re-resolve the executable. How can we be assured that the debugger and the RTT decoder is looking at the same executable? Do you need help from the debugger?

Also, I think that the executable property in launch.json is optional if you have the symbolFiles property.

[xoviat]

I'll get back to this in a few days. I need to refresh my memory after taking care of some other stuff.

[HaoboGu]

Any updates? I got the same problem, cortex-debug cannot print defmt's RTT log

[hazer-hazer]

Installed extension from this PR, everything works perfectly, except vscode does not hint to set defmt as type option in rttConfig.decoders.
@Marus Any chance to see this changes in master? 💌

[haneefdm]

@xoviat I am still waiting for the PRs original author.

[romancardenas]

Any news here? Can I help with any blocker?

[wrs]

For those waiting on this, I wrote a comment on the old issue explaining how to get defmt working with the released cortex-debug.

#755 (comment)

[tpilt]

Looking very much forward to this!

For those waiting on this, I wrote a comment on the old issue explaining how to get defmt working with the released cortex-debug.

This is now further simplified by 'tcp' parameter on defmt-print:
$ defmt-print -w -e target/thumbv7em-none-eabi/debug/blinky tcp

[newcomertv]

So the blocker is this? :

Also, I think that the executable property in launch.json is optional if you have the symbolFiles property.

I think OP is gone. Not a TS dev though if this is the only thing I can maybe have a look and file a PR that can get merged.

[GreenCappuccino]

Hello all,

Using the (newer?) advanced decoder described here:

"rttConfig": {
"enabled": true,
"address": "auto",
"decoders": [
{
"type": "advanced",
"decoder": "./rtt-defmt.js",
"config": {
"cwd": "${workspaceRoot}",
"executable": "./target/thumbv8m.main-none-eabihf/debug/interchange",
},
"label": "RTT",
"port": 0,
"ports": [0]
},
]
},

Where I've written an implementation rtt-defmt.js:

constChildProcess=require('child_process');constPath=require('path');constvscode=require('vscode');classDefmtDecoder{constructor(){this.config={};this.displayOutput=()=>{};this.graphData=()=>{};this.process=null;}init(config,displayOutput,graphData){this.config=config;this.displayOutput=displayOutput;this.graphData=graphData;this.cwd=config.config.cwd||process.cwd();if(!config.config.executable){thrownewError(JSON.stringify(config));}this.executable=Path.resolve(this.cwd,config.config.executable);this.process=ChildProcess.spawn('defmt-print',['-e',this.executable],{cwd: this.cwd});this.process.stdout.on('data',(data)=>{this.displayOutput(data.toString());});this.process.stderr.on('data',(data)=>{this.displayOutput(`stderr: ${data.toString()}`);});this.process.on('error',(error)=>{this.displayOutput(`Error: ${error.message}\n`);});}softwareEvent(_port,data){if(!this.process||!this.process.stdin){if(this.outputChannel){this.displayOutput('Error: defmt-print process is not running.\n');}return;}letbufferInput=Buffer.isBuffer(data) ? data : Buffer.from(data);this.process.stdin.write(bufferInput);}outputLabel(){returnthis.config.label;}typeName(){return'defmt-print';}}module.exports={default: DefmtDecoder};

I have a solution that I prefer, where a new output channel (in this case named SWO: RTT [type defmt-print]) is created in the VS code OUTPUT tab with correct defmt-print output.

The implementation, when initialized, creates a new defmt-print process, which it uses to drive the VS code output channel.

[rhuys]

I have the same problem.
probe-rs is not mature enough to be used reliably for debugging, but RTT and DEFMT are essential to work.
Please include DEFMT decoding in cortex-debug.

[haneefdm]

Built-in RTT with dfmt-print is coming. This extension is getting a rewrite. Don't want to disturb cortex-debug in a major way as it is used in production by many people. The new extension will be available soon for download here (alpha) and then Beta in the Marketplace. It will be bit of a journey.

https://github.com/mcu-debug/mcu-debug
https://mcu-debug.github.io/mcu-debug/docs/getting-started
https://mcu-debug.github.io/mcu-debug/docs/tracing/rtt#defmt-support

For now, it is best to use the solution by @GreenCappuccino

[rhuys]

@GreenCappuccino thanks for your solution, it works,
but now VSCODE starts a new output tab every time I re-run my application,
do you have an idea on how to re-use the same tab?