83 lines
2.7 KiB
Plaintext
83 lines
2.7 KiB
Plaintext
= Frequently Asked Questions
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These are a list of unsorted, commonly asked questions and answers.
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Please feel free to add items to link:https://github.com/embassy-rs/embassy/edit/main/docs/modules/ROOT/pages/faq.adoc[this page], especially if someone in the chat answered a question for you!
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== How to deploy to RP2040 without a debugging probe.
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Install link:https://github.com/JoNil/elf2uf2-rs[elf2uf2-rs] for converting the generated elf binary into a uf2 file.
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Configure the runner to use this tool, add this to `.cargo/config.toml`:
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[source,toml]
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----
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[target.'cfg(all(target_arch = "arm", target_os = "none"))']
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runner = "elf2uf2-rs --deploy --serial --verbose"
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----
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The command-line parameters `--deploy` will detect your device and upload the binary, `--serial` starts a serial connection. See the documentation for more info.
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== Missing main macro
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If you see an error like this:
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[source,rust]
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----
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#[embassy_executor::main]
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| ^^^^ could not find `main` in `embassy_executor`
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----
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You are likely missing some features of the `embassy-executor` crate.
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For Cortex-M targets, consider making sure that ALL of the following features are active in your `Cargo.toml` for the `embassy-executor` crate:
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* `arch-cortex-m`
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* `executor-thread`
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* `nightly`
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For Xtensa ESP32, consider using the executors and `#[main]` macro provided by your appropriate link:https://crates.io/crates/esp-hal-common[HAL crate].
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== Why is my binary so big?
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The first step to managing your binary size is to set up your link:https://doc.rust-lang.org/cargo/reference/profiles.html[profiles].
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[source,toml]
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----
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[profile.release]
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debug = false
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lto = true
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opt-level = "s"
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incremental = true
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----
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All of these flags are elaborated on in the Rust Book page linked above.
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=== My binary is still big... filled with `std::fmt` stuff!
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This means your code is sufficiently complex that `panic!` invocation's formatting requirements could not be optimized out, despite your usage of `panic-halt` or `panic-reset`.
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You can remedy this by adding the following to your `.cargo/config.toml`:
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[source,toml]
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----
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[unstable]
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build-std = ["core"]
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build-std-features = ["panic_immediate_abort"]
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----
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This replaces all panics with a `UDF` (undefined) instruction.
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Depending on your chipset, this will exhibit different behavior.
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Refer to the spec for your chipset, but for `thumbv6m`, it results in a hardfault. Which can be configured like so:
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[source,rust]
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----
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#[exception]
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unsafe fn HardFault(_frame: &ExceptionFrame) -> ! {
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SCB::sys_reset() // <- you could do something other than reset
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}
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----
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Refer to cortex-m's link:https://docs.rs/cortex-m-rt/latest/cortex_m_rt/attr.exception.html[exception handling] for more info.
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