Use probe-run-rp and defmt.

Author: thejpster

.cargo/config.toml

@@ -1,5 +1,6 @@
 [target.thumbv6m-none-eabi]
-runner = "elf2uf2-rs -d"
+# runner = "elf2uf2-rs -d"
+runner = "probe-run-rp --chip RP2040"
 
 rustflags = [
   # This is needed if your flash or ram addresses are not aligned to 0x10000 in memory.x
@@ -8,6 +9,9 @@ rustflags = [
 
   # LLD (shipped with the Rust toolchain) is used as the default linker
   "-C", "link-arg=-Tlink.x",
+
+  # Support defmt formatted logging
+  "-C", "link-arg=-Tdefmt.x",
 ]
 
 [build]

CHANGELOG.md

@@ -2,7 +2,8 @@
 
 ## Unreleased Changes ([Source](https://github.com/neotron-compute/neotron-pico-bios/tree/master) | [Changes](https://github.com/neotron-compute/neotron-pico-bios/compare/v0.1.0...master))
 
-* None
+* Add RTT debugging
+* Describe how to flash/debug with a second Raspberry Pi Pico
 
 ## v0.1.0 ([Source](https://github.com/neotron-compute/neotron-pico-bios/tree/v0.1.0) | [Release](https://github.com/neotron-compute/neotron-pico-bios/release/tag/v0.1.0))
 

Cargo.toml

@@ -19,10 +19,30 @@ neotron-common-bios = { git = "https://github.com/Neotron-Compute/Neotron-Common
 embedded-time = "0.12"
 # For the RP2040 bootloader
 rp2040-boot2 = "0.1"
-# For panic handling (todo remove this)
-panic-halt = "0.2"
 # For hardware abstraction traits
 embedded-hal ="0.2"
+# Gives us formatted PC-side logging
+defmt = "0.2"
+# Sends defmt logs to the SWD debugger
+defmt-rtt = "0.2"
+# Send panics to the debugger
+panic-probe = "0.2"
+
+[features]
+default = [
+    "defmt-default",
+]
+defmt-default = []
+# Enables trace logs
+defmt-trace = []
+# Enables debug logs
+defmt-debug = []
+# Enables info logs
+defmt-info = []
+# Enables warn logs
+defmt-warn = []
+# Enables error logs
+defmt-error = []
 
 [[bin]]
 name = "neotron-pico-bios"

README.md

@@ -35,6 +35,46 @@ Currently the BIOS only uses a single core, and starts the OS on the same core.
 Later versions may move some functionality onto the second core (e.g. screen
 updates) for performance reasons.
 
+## Programming
+
+The Neotron BIOS uses the [defmt](https://crates.io/crates/defmt) crate to provide structured logging over the SWD interface. The easiest way to flash and debug your Neotron Pico BIOS is with a second Raspberry Pi Pico.
+
+1. Connect your *Debugger* Pico to the *Neotron* Pico:
+    * connect Pin 3 on the *Debugger* Pico to GND on the *Neotron* Pico
+    * connect Pin 4 on the *Debugger* Pico to SWCLK on the *Neotron* Pico
+    * connect Pin 5 on the *Debugger* Pico to SWDIO on the *Neotron* Pico
+    * connect USB on the *Debugger* Pico to your PC
+
+2. Flash your *Debugger* Pico with https://github.com/majbthrd/DapperMime firmware (e.g. by copying the UF2 file to the USB Mass Storage device)
+
+3. On your PC, install *probe-rs-rp* from the RP2040-specific [probe-run](https://github.com/knurling-rs/probe-run) fork at https://github.com/rp-rs/probe-run.
+
+```console
+user@host ~ $ cargo install probe-rs-rp
+```
+
+4. Power on your Neotron Pico.
+
+5. Build and load the Neotron BIOS, and view the debug output stream, with `cargo run`:
+
+```console
+user@host ~/neotron-pico-bios $ cargo run --release
+   Compiling neotron-pico-bios v0.1.0 (/home/jonathan/Documents/neotron/neotron-pico-bios)
+    Finished release [optimized + debuginfo] target(s) in 0.76s
+     Running `probe-run-rp --chip RP2040 target/thumbv6m-none-eabi/release/neotron-pico-bios`
+(HOST) INFO  flashing program (7.30 KiB)
+(HOST) INFO  success!
+────────────────────────────────────────────────────────────────────────────────
+ INFO  Neotron BIOS starting...
+└─ neotron_pico_bios::__cortex_m_rt_main @ src/main.rs:79
+ INFO  Clocks OK
+└─ neotron_pico_bios::__cortex_m_rt_main @ src/main.rs:102
+ INFO  Pins OK
+└─ neotron_pico_bios::__cortex_m_rt_main @ src/main.rs:121
+ DEBUG Loop...
+└─ neotron_pico_bios::__cortex_m_rt_main @ src/main.rs:128
+``` 
+
 ## Changelog
 
 See [CHANGELOG.md](./CHANGELOG.md)

src/main.rs

@@ -38,10 +38,12 @@
 // -----------------------------------------------------------------------------
 
 use cortex_m_rt::entry;
+use defmt::*;
+use defmt_rtt as _;
 use embedded_hal::digital::v2::OutputPin;
 use embedded_time::rate::*;
 use hal::clocks::Clock;
-use panic_halt as _;
+use panic_probe as _;
 use pico;
 use pico::hal;
 use pico::hal::pac;
@@ -74,6 +76,8 @@ pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER;
 /// `.bss` and `.data` sections have been initialised.
 #[entry]
 fn main() -> ! {
+	info!("Neotron BIOS starting...");
+
 	// Grab the singleton containing all the RP2040 peripherals
 	let mut pac = pac::Peripherals::take().unwrap();
 	// Grab the singleton containing all the generic Cortex-M peripherals
@@ -95,6 +99,8 @@ fn main() -> ! {
 	.ok()
 	.unwrap();
 
+	info!("Clocks OK");
+
 	// Create an object we can use to busy-wait for specified numbers of
 	// milliseconds. For this to work, it needs to know our clock speed.
 	let mut delay = cortex_m::delay::Delay::new(core.SYST, clocks.system_clock.freq().integer());
@@ -112,11 +118,14 @@ fn main() -> ! {
 		&mut pac.RESETS,
 	);
 
+	info!("Pins OK");
+
 	// Grab the LED pin
 	let mut led_pin = pins.led.into_push_pull_output();
 
 	// Do some blinky so we can see it work.
 	loop {
+		debug!("Loop...");
 		led_pin.set_high().unwrap();
 		delay.delay_ms(500);
 		led_pin.set_low().unwrap();