Also print panic to the defmt channel

panic-rtt-target/Cargo.toml

@@ -16,3 +16,12 @@ repository = "https://github.com/probe-rs/rtt-target"
 rtt-target = {version = "0.6.0", path = "../rtt-target" }
 critical-section = "1.1.1"
 portable-atomic = { version = "1.6.0", default-features = false }
+
+defmt = { version = "0.3.0", optional = true }
+
+[features]
+default = []
+defmt = ["dep:defmt"]
+
+[package.metadata.docs.rs]
+features = ["defmt"]

panic-rtt-target/README.md

@@ -37,3 +37,10 @@ fn main() -> ! {
     panic!("Something has gone terribly wrong");
 }
 ```
+
+# Defmt support
+
+You can enable the `defmt` feature so that panics are printed to the defmt channel. If you do this
+and have configured both a print and a defmt channel, the panic message will be printed to both.
+The `defmt` feature doesn't automatically enable `rtt-target/defmt`. This allows you to use a
+different defmt backend if needed.

panic-rtt-target/src/lib.rs

@@ -3,8 +3,9 @@
 //! RTT must have been initialized by using one of the `rtt_init` macros. Otherwise you will get a
 //! linker error at compile time.
 //!
-//! Panics are always logged to the print channel. Upon panicking the channel mode is also
-//! automatically set to `BlockIfFull`, so that the full message will always be logged.
+//! Panics are always logged to the print and defmt channels, if they are configured. Upon panicking
+//! the channel mode is also automatically set to `BlockIfFull`, so that the full message will
+//! always be logged.
 //! If the code somehow manages to panic at runtime before RTT is initialized (quite unlikely),
 //! or if the print channel doesn't exist, nothing is logged.
 //!
@@ -48,6 +49,9 @@ use rtt_target::{with_terminal_channel, ChannelMode};
 #[panic_handler]
 fn panic(info: &PanicInfo) -> ! {
     critical_section::with(|_| {
+        #[cfg(feature = "defmt")]
+        defmt::error!("{}", defmt::Display2Format(info));
+
         with_terminal_channel(|term| {
             term.set_mode(ChannelMode::BlockIfFull);
             let mut channel = term.write(0);