probe-run on an Arduino Nano 33 BLE?

[bryanburgers]

Describe the bug

I'm not quite sure where to ask this, because I think it's more of a "new to embedded development" question more than anything.

I'm trying to get started programming an Arduino Nano 33 BLE in Rust. It looks like the Nano 33 is a nRF52840_xxAA, which seems to be a supported chipset.

I have it hooked up via USB to my Mac and I can flash to it via the Arduino IDE (first new-to-this question as I was digging around trying to understand what's going on: is that because this chip comes pre-flashed with some Arduino bootloader?)

When I do a cargo run, I get

$ cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.03s
     Running `probe-run --chip nRF52840_xxAA target/thumbv7em-none-eabi/debug/arduino-nano-test`
Error: no probe was found

probe-run --list-probes tells me that no devices were found. I can't tell if that's expected or if I need to do something else or if I'm completely out in left field.

$ probe-run --verbose --list-probes
No devices were found.
$ probe-rs-cli list
No devices were found.

I remember a previous co-worker at a previous job explaining things like J-Link to me; does probe-run only work with one of those things? Or should I expect probe-run to work directly connected to the Nano's USB port? Do I need to somehow flash a different bootloader onto the device first (I've seen avrdude mentioned...)?

main.rs

#![no_std]
#![no_main]

use cortex_m::asm;
use cortex_m_rt::entry;
use rtt_target::{rprintln, rtt_init_print};
use nrf52840_hal as _;

#[panic_handler]
fn panic(_info: &core::panic::PanicInfo) -> ! {
    loop {
        asm::bkpt()
    }
}

#[entry]
fn main() -> ! {
    rtt_init_print!();
    rprintln!("Hello, world!");

    loop {
        asm::bkpt()
    }
}

Cargo.toml

[package]
name = "arduino-nano-test"
version = "0.1.0"
authors = ["Bryan Burgers <bryan@burgers.io>"]
edition = "2018"

[dependencies]
cortex-m = "0.7"
cortex-m-rt = "0.6"
rtt-target = { version = "0.3", features = ["cortex-m"] }
nrf52840-hal = "0.12"

config.toml
The contents of your project's .cargo/config.toml file

[target.'cfg(all(target_arch = "arm", target_os = "none"))']
runner = "probe-run --chip nRF52840_xxAA"
rustflags = [
  "-C", "link-arg=-Tlink.x",
]

[build]
# target = "thumbv7em-none-eabihf"  # I think it's an hf, but also saw somewhere that hf wasn't supported and need to workaround without it, but maybe that was old news
target = "thumbv7em-none-eabi"

Probe details

$ probe-rs-cli list
No devices were found

Operating System:
macOS 11.2 (Big Sur)

$ uname -ap
Darwin Bryans-MacBook-Pro.local 20.3.0 Darwin Kernel Version 20.3.0: Thu Jan 21 00:07:06 PST 2021; root:xnu-7195.81.3~1/RELEASE_X86_64 x86_64 i386

[japaric]

Hello!

To use probe-run you need a "probe" (also known as "debugger") that sits between your PC and the microcontroller (the nRF52840 in your case). Most development boards, specially the bigger ones, have a probe "on-board" so after you connect your PC to the dev board using a USB cable you are all set and can use probe-run.

This particular board (the Arduino Nano 33 BLE) does not come with an on-board probe. When that's the case you'll need to connect a "stand alone" probe (additional piece of hardware) 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. (There are also CMSIS-DAP based probes but I'm not aware of any stand alone probe that adheres to the CMSIS DAP standard)

Looking at the schematic of this board: https://content.arduino.cc/assets/NANO33BLE_V2.0_sch.pdf
There are SWD pins (SWDCLK and SWDIO) routed to connector J3. You'll need to connect those SWD pins and GND to the standalone probe to be able to use probe-run.

Now, I don't see "J3" printed on the board when looking at the pictures of the board. J3 may or may not be the 4 square solder pads on the back of the board that sit between "D6" and "D9".

I would ask on the Arduino forums how one can connect a stand alone debugger to this board. Or if they have some accessory for this.
If they say that the only way to load a new program on the board is using a "bootloader" then this board is not supported by probe-run at the moment and would fall in the same group as the Teensy boards (see #22).

Hope that helps!

[bryanburgers]

@japaric Yes, that is actually very helpful, and helps me understand the difference between "I'm doing this wrong" and "My board doesn't support this".

I really appreciate you taking the time to look into this and help me understand what's going on.

I don't think my hobbying quite merits buying an ST-Link or J-Link and soldering something onto my boards, so I'll look into different ways to start experimenting (probably avrdude somehow).

Thanks again for your time! I really appreciate it.