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# `probe-run`
> Runs embedded programs just like native ones
`probe-run` is a custom Cargo runner that transparently runs Rust firmware on a
remote device.
`probe-run` is powered by [`probe-rs`] and thus supports as many devices and probes as
`probe-rs` does.
[`probe-rs`]: https://probe.rs/
## Features
* Acts as a Cargo runner, integrating into `cargo run`.
* Displays program output streamed from the device via RTT.
* Exits the firmware and prints a stack backtrace on breakpoints.
## Installation
To install `probe-run`, use `cargo install probe-run`.
On Linux, you might have to install `libudev` and `libusb` from your package
manager before installing `probe-run`.
``` console
# ubuntu
$ sudo apt install -y libusb-1.0-0-dev libudev-dev
# fedora
$ sudo dnf install -y libusbx-devel systemd-devel
```
## Setup
### 1. Set the Cargo runner
The recommend way to use `probe-run` is to set as the Cargo runner of your application.
Add these two lines to your Cargo configuration file (`.cargo/config.toml`) and set the particular `--chip` value for your target. In this case it is `nRF52840_xxAA` for the [nRF52840]:
``` toml
[target.'cfg(all(target_arch = "arm", target_os = "none"))']
runner = "probe-run --chip nRF52840_xxAA"
# ^^^^^^^^^^^^^
```
To list all supported chips run `probe-run --list-chips`.
#### **1.1 Env variable**
To support multiple devices, or permit overriding default behavior, you may prefer to:
1. set the `${PROBE_RUN_CHIP}` environment variable, and
2. set `runner` (or `CARGO_TARGET_${TARGET_ARCH}_RUNNER`) to `probe-run`:
``` toml
[target.'cfg(all(target_arch = "arm", target_os = "none"))']
runner = "probe-run"
```
#### **1.2 Multiple probes**
If you have several probes connected, you can specify which one to use by adding the `--probe` option to the `runner` or setting the `${PROBE_RUN_PROBE}` environment variable with a value containing either `${VID}:${PID}` or `${VID}:${PID}:${SERIAL}`:
```console
// --probe
$ probe-run --probe '0483:3748' --chip ${PROBE_RUN_CHIP}
// PROBE_RUN_PROBE
$ PROBE_RUN_PROBE='1366:0101:123456' cargo run
```
To list all connected probes, run `probe-run --list-probes`.
[nRF52840]: https://www.nordicsemi.com/Products/Low-power-short-range-wireless/nRF52840
### 2. Enable debug info
Next check that debug info is enabled for all profiles.
If you are using the `cortex-m-quickstart` template then this is already the case.
If not check or add these lines to `Cargo.toml`.
``` toml
[dependencies]
...
panic-probe = { version = "0.2", features = ["print-rtt"] }
# Cargo.toml
[profile.dev]
debug = 1 # default is `true`; not needed if not already overridden
[profile.release]
debug = 1 # default is `false`; using `true` is also OK as symbols reside on the host, not the target
```
### 3. Look out for old dependencies
The `cortex-m` dependency must be version 0.6.3 or newer.
Older versions are not supported.
Check your `Cargo.lock` for old versions.
Run `cargo update` to update the `cortex-m` dependency if an older one appears in `Cargo.lock`.
### 4. Run
You are all set.
You can now run your firmware using `cargo run`.
For example,
``` rust
use cortex_m::asm;
use cortex_m_rt::entry;
use panic_probe as _;
use rtt_target::rprintln;
#[entry]
fn main() -> ! {
rtt_init_print!(); // You may prefer to initialize another way
rprintln!("Hello, world!");
loop { asm::bkpt() }
}
```
would output
``` console
$ cargo run --bin hello
Finished dev [unoptimized + debuginfo] target(s) in 0.07s
Running `probe-run --chip nRF52840_xxAA target/thumbv7em-none-eabihf/debug/hello`
(HOST) INFO flashing program (30.22 KiB)
(HOST) INFO success!
────────────────────────────────────────────────────────────────────────────────
INFO:hello -- Hello, world!
────────────────────────────────────────────────────────────────────────────────
(HOST) INFO exiting because the device halted.
To see the backtrace at the exit point repeat this run with
`probe-run --chip nRF52840_xxAA target/thumbv7em-none-eabihf/debug/hello --force-backtrace`
```
## Stack backtraces
When the device raises a hard fault exception, indicating e.g. a panic or a stack overflow, `probe-run` will print a backtrace and exit with a non-zero exit code.
This backtrace follows the format of the `std` backtraces you get from `std::panic!` but includes
`<exception entry>` lines to indicate where an exception/interrupt occurred.
``` rust
#![no_main]
#![no_std]
use cortex_m::asm;
#[entry]
fn main() -> ! {
// trigger a hard fault exception with the UDF instruction.
asm::udf()
}
```
``` console
Finished dev [optimized + debuginfo] target(s) in 0.04s
Running `probe-run --chip nRF52840_xxAA target/thumbv7em-none-eabihf/debug/hard-fault`
(HOST) INFO flashing program (30.08 KiB)
(HOST) INFO success!
────────────────────────────────────────────────────────────────────────────────
stack backtrace:
0: HardFaultTrampoline
<exception entry>
1: __udf
2: cortex_m::asm::udf
at /<...>/cortex-m-0.6.4/src/asm.rs:104
3: panic::__cortex_m_rt_main
at src/bin/hard-fault.rs:12
4: main
at src/bin/hard-fault.rs:8
5: ResetTrampoline
at /<...>3/cortex-m-rt-0.6.13/src/lib.rs:547
6: Reset
at /<...>/cortex-m-rt-0.6.13/src/lib.rs:550
```
If we look at the return code emitted by this `cargo run`, we'll see that it is non-0:
```console
$ echo $?
134
```
⚠️ **NOTE** when you run your application with `probe-run`, the `HardFault` handler (default or user-defined) will *NOT* be executed.
### Forcing backtraces
If you'd like to see a backtrace at the end of successful program runs as well, you can enable this by setting the `--force-backtrace` flag:
``` console
$ cargo run --bin hello --force-backtrace
```
## Troubleshooting
### `probe-run --list-probes` says "No devices were found."
Apart from a faulty connection between your computer and the target device, this could be caused by several things:
#### [Linux only] udev rules haven't been set
In order for `probe-run` to find the device you'd like to run your code on, your system needs permission to access the device as a non-root user.
In order to grant these permissions, you'll need to add a new set of udev rules.
To learn how to do this for the nRF52840 Development Kit, check out the [installation instructions](https://embedded-trainings.ferrous-systems.com/installation.html?highlight=udev#linux-only-usb) in our embedded training materials.
#### No external or on-board debugger present
To use `probe-run` you need a "probe" (also known as "debugger") that sits between your PC and the microcontroller.
Most development boards, especially the bigger ones, have a probe "on-board": If the product description of your board mentions something like a J-Link or ST-Link on-board debugger you're good to go. With these boards, all you need to do is connect your PC to the dev board using a USB cable you are all set to use `probe-run`!
If this is *not* the case for your board, check in the datasheet if it exposes exposes SWD or JTAG pins.
If they are exposed, you can connect a "stand alone" probe device to the microcontroller and then connect the probe to your PC via USB. Some examples of stand alone probes are: the ST-Link and the J-Link.
Note that this may involve some soldering if your board does not come with a pre-attached header to plug your debugger into.
### Error: RTT up channel 0 not found
This may instead present as `Error: RTT control block not found in target memory.`
Your code, or a library you're using (e.g. RTIC) might be putting your CPU to
sleep when idle. You can verify that this is the problem by busy looping instead
of sleeping. When using RTIC, this can be achieved by adding an idle handler to
your app:
```rust
#[idle]
fn idle(_ctx: idle::Context) -> ! {
loop {}
}
```
Assuming you'd like to still sleep in order to save power, you need to configure
your microcontroller so that RTT can still be handled even when the CPU is
sleeping. How to do this varies between microcontrollers.
On an STM32G0 running RTIC it can be done by amending your init function to set
the `dmaen` bit on `RCC.ahbenr`. e.g.:
```rust
#[init]
fn init(ctx: init::Context) -> init::LateResources {
ctx.device.RCC.ahbenr.write(|w| w.dmaen().set_bit());
...
}
```
### defmt version mismatch
#### end-user
Follow the instructions in the error message to resolve the mismatch.
#### developer
If you are hacking around with `probe-run`, you can disable the version check by setting the `PROBE_RUN_IGNORE_VERSION` environment variable to `true` or `1` at runtime.
## Developer Information
### running your locally modified `probe-run`
For easier copy-paste-ability, here's an example how to try out your local `probe_run` modifications.
```console
$ cd probe-run/
$ PROBE_RUN_IGNORE_VERSION=1 cargo run -- --chip nRF52840_xxAA --max-backtrace-len=10 hello
ˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆ ˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆˆ ˆˆˆˆˆ
environment variables extra flags binary to be
(optional) (optional) flashed & run
```
### running snapshot tests
To check whether your change has altered probe-run in unexpected ways, please run the snapshot tests in `tests` before opening a PR if at all possible.
You can do so by connecting a nrf52840 Development Kit and running
```console
$ cargo test -- --ignored
```
## Support Us
`probe-run` is part of the [Knurling] project, [Ferrous Systems]' effort at
improving tooling used to develop for embedded systems.
If you think that our work is useful, consider sponsoring it via [GitHub
Sponsors].
## License
Licensed under either of
- Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or
http://www.apache.org/licenses/LICENSE-2.0)
- MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
at your option.
### Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
licensed as above, without any additional terms or conditions.
[Knurling]: https://knurling.ferrous-systems.com
[Ferrous Systems]: https://ferrous-systems.com/
[GitHub Sponsors]: https://github.com/sponsors/knurling-rs