embassy-rs/embassy · error

failed to find dma interrupt for channel

Error message

failed to find dma interrupt for channel {}

What it means

While generating DMA channel traits, build.rs maps each DMA channel to its interrupt (IRQ) name via a `dma_ch_to_irq` lookup built from chip metadata. If a DMA channel has no associated interrupt entry, the script panics naming the channel. It indicates a gap in the chip's interrupt/DMA metadata, so the channel can't be wired to an interrupt handler.

Solutions

1. Check embassy-stm32's per-chip metadata and add the missing DMA-channel-to-interrupt mapping.
2. Verify you're on the latest embassy-stm32 — the chip's metadata may have been fixed upstream.
3. As a workaround, use a different DMA channel whose interrupt mapping exists.

Example fix

// metadata: ch "GPDMA1_CHANNEL7" has no IRQ entry
// before (chip data): { name: "GPDMA1_CHANNEL7", ... } // no irq
// after: add "GPDMA1_CHANNEL7" => ["GPDMA1_CHANNEL7"] to the dma irq mapping

// check the chip's DMA channel -> IRQ mapping exists before using that channel
// in embassy-stm32 data: dma_ch_to_irq must contain ch.name

When it happens

Trigger: Building with DMA for a chip whose metadata lists a DMA/GPDMA/LPDMA channel without any matching interrupt in the interrupt table, so `.get(ch.name).and_then(|v| v.first())` is None.

Common situations: Newly added STM32 parts with incomplete DMA-to-IRQ metadata; channels shared across cores (dual-core parts) where the mapping wasn't populated.

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

• bad dma channel kind
• DMA data error
• Pin has no IOMUXC definitions
• DMA: error on DMA_0 channel
• DMA: error on DMA_0 channel

AI-assisted analysis of embassy-rs/embassy@463a07b963 (2026-09-10). Data as JSON: /api/errors/55eec77c9886e8bc. Report an issue: GitHub.

Appendix: source

Thrown at embassy-stm32/build.rs:2684

        let stop_mode = dma_peri
            .rcc
            .as_ref()
            .map(|rcc| rcc.stop_mode.clone())
            .unwrap_or_default();

        let stop_mode = match stop_mode {
            StopMode::Standby => quote! { Standby },
            StopMode::Stop2 => quote! { Stop2 },
            StopMode::Stop1 => quote! { Stop1 },
        };

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

        // Get the interrupt type for this DMA channel
        let irq_name = dma_ch_to_irq
            .get(ch.name)
            .and_then(|v| v.first())
            .unwrap_or_else(|| panic!("failed to find dma interrupt for channel {}", ch.name));
        let irq_ident = format_ident!("{}", irq_name);
        let irq_type = quote!(crate::interrupt::typelevel::#irq_ident);

        #[cfg(feature = "_dual-core")]
        let irq_pac = quote!(crate::pac::Interrupt::#irq_ident);

        g.extend(quote!(dma_channel_impl!(#name, #irq_type);));

        if ch.supports_2d.unwrap_or(false) {
            g.extend(quote!(dma_channel_2d_impl!(#name);));
        }

        let dma = format_ident!("{}", ch.dma);
        let ch_num = ch.channel as usize;
        let bi = dma_peri.registers.as_ref().unwrap();

        if ch.supports_2d.unwrap_or(false) && bi.kind == "gpdma" {
            has_gpdma_2d = true;

View on GitHub (pinned to 463a07b963)