embassy-rs/embassy · error

Could not find DEBUGSS peripheral

Error message

Could not find DEBUGSS peripheral

What it means

pin_features then looks up the DEBUGSS peripheral in the chip metadata to gate SWD pins behind the swd-pins-as-gpio feature, and panics when DEBUGSS is missing. Every supported MSPM0 package is expected to expose a DEBUGSS entry describing the SWD/swap pins.

Solutions

1. Add the DEBUGSS peripheral (with its SWCLK/SWDIO pin signals) to the chip metadata and rebuild.
2. Regenerate the chip metadata so the debug subsystem is included.
3. If upstream metadata is at fault, report it so the generator emits DEBUGSS for this package.

Example fix

// before: peripherals list without DEBUGSS
// after (metadata YAML)
- name: DEBUGSS
  pins:
    - { signal: SWCLK, pin: PA20 }
    - { signal: SWDIO, pin: PA19 }

assert!(metadata.peripherals.iter().any(|p| p.name == "DEBUGSS"), "chip metadata missing DEBUGSS");

When it happens

Trigger: Building embassy-mspm0 for a package whose metadata peripheral list lacks an entry named "DEBUGSS", so METADATA.peripherals.iter().find(|p| p.name == "DEBUGSS").expect(...) panics in generate_code -> pin_features.

Common situations: Metadata for a new MSPM0 variant that omits the DEBUGSS peripheral; a metadata regeneration tool that skips debug subsystem entries; hand-trimming the peripheral list and removing DEBUGSS.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

• Could not find any timer
• no SYSCTL peripheral
• Could not find NRST pin to cfg gate
• Could not find SWD pin to cfg gate
• Timer does not exist

AI-assisted analysis of embassy-rs/embassy@463a07b963 (2026-09-10). Data as JSON: /api/errors/14e6a3a3909fcdf4. Report an issue: GitHub.

Appendix: source

Thrown at embassy-mspm0/build.rs:528

        .iter()
        .find(|p| p.name == "SYSCTL")
        .expect("no SYSCTL peripheral");

    // Some packages make NRST share a physical pin with a GPIO.
    if let Some(pin) = sysctl.pins.iter().find(|p| p.signal == "NRST" && p.pin != "NRST") {
        let pin = singletons
            .iter_mut()
            .find(|s| s.name == pin.pin)
            .expect("Could not find NRST pin to cfg gate");

        pin.cfg = Some(quote! { #[cfg(feature = "nrst-pin-as-gpio")] });
    }

    let debugss = METADATA
        .peripherals
        .iter()
        .find(|p| p.name == "DEBUGSS")
        .expect("Could not find DEBUGSS peripheral");

    for pin in debugss.pins.iter() {
        let pin = singletons
            .iter_mut()
            .find(|s| s.name == pin.pin)
            .expect("Could not find SWD pin to cfg gate");

        pin.cfg = Some(quote! { #[cfg(feature = "swd-pins-as-gpio")] });
    }
}

fn generate_singletons(singletons: &[Singleton]) -> TokenStream {
    let singletons_peripherals_struct = singletons
        .iter()
        .map(|s| {
            let cfg = s.cfg.clone().unwrap_or_default();

            let ident = format_ident!("{}", s.name);

View on GitHub (pinned to 463a07b963)