155 lines
6.4 KiB
Plaintext
155 lines
6.4 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 = false
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codegen-units = 1
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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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== `embassy-time` throws linker errors
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If you see linker error like this:
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[source,text]
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----
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= note: rust-lld: error: undefined symbol: _embassy_time_now
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>>> referenced by driver.rs:127 (src/driver.rs:127)
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>>> embassy_time-846f66f1620ad42c.embassy_time.4f6a638abb75dd4c-cgu.0.rcgu.o:(embassy_time::driver::now::hefb1f99d6e069842) in archive Devel/Embedded/pogodyna/target/thumbv7em-none-eabihf/debug/deps/libembassy_time-846f66f1620ad42c.rlib
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rust-lld: error: undefined symbol: _embassy_time_allocate_alarm
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>>> referenced by driver.rs:134 (src/driver.rs:134)
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>>> embassy_time-846f66f1620ad42c.embassy_time.4f6a638abb75dd4c-cgu.0.rcgu.o:(embassy_time::driver::allocate_alarm::hf5145b6bd46706b2) in archive Devel/Embedded/pogodyna/target/thumbv7em-none-eabihf/debug/deps/libembassy_time-846f66f1620ad42c.rlib
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rust-lld: error: undefined symbol: _embassy_time_set_alarm_callback
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>>> referenced by driver.rs:139 (src/driver.rs:139)
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>>> embassy_time-846f66f1620ad42c.embassy_time.4f6a638abb75dd4c-cgu.0.rcgu.o:(embassy_time::driver::set_alarm_callback::h24f92388d96eafd2) in archive Devel/Embedded/pogodyna/target/thumbv7em-none-eabihf/debug/deps/libembassy_time-846f66f1620ad42c.rlib
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rust-lld: error: undefined symbol: _embassy_time_set_alarm
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>>> referenced by driver.rs:144 (src/driver.rs:144)
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>>> embassy_time-846f66f1620ad42c.embassy_time.4f6a638abb75dd4c-cgu.0.rcgu.o:(embassy_time::driver::set_alarm::h530a5b1f444a6d5b) in archive Devel/Embedded/pogodyna/target/thumbv7em-none-eabihf/debug/deps/libembassy_time-846f66f1620ad42c.rlib
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----
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You probably need to enable a time driver for your HAL (not in `embassy-time`!). For example with `embassy-stm32`, you might need to enable `time-driver-any`:
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[source,toml]
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----
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[dependencies.embassy-stm32]
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version = "0.1.0"
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features = [
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# ...
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"time-driver-any", # Add this line!
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# ...
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]
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----
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== Error: `Only one package in the dependency graph may specify the same links value.`
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You have multiple versions of the same crate in your dependency tree. This means that some of your
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embassy crates are coming from crates.io, and some from git, each of them pulling in a different set
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of dependencies.
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To resolve this issue, make sure to only use a single source for all your embassy crates! To do this,
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you should patch your dependencies to use git sources using `[patch.crates.io]` and maybe `[patch.'https://github.com/embassy-rs/embassy.git']`.
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Example:
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[source,toml]
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----
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[patch.crates-io]
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embassy-time = { git = "https://github.com/embassy-rs/embassy.git", rev = "e5fdd35" }
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----
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Note that the git revision should match any other embassy patches or git dependencies that you are using!
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== How can I optimize the speed of my embassy-stm32 program?
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* Make sure RCC is set up to go as fast as possible
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* Make sure link:https://docs.rs/cortex-m/latest/cortex_m/peripheral/struct.SCB.html[flash cache] is enabled
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* build with `--release`
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* Set the following keys for the release profile in your `Cargo.toml`:
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** `opt-level = "s"`
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** `lto = "fat"`
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* Set the following keys in the `[unstable]` section of your `.cargo/config.toml`
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** `build-std = ["core"]`
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** `build-std-features = ["panic_immediate_abort"]`
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* Enable feature `embassy-time/generic-queue`, disable feature `embassy-executor/integrated-timers`
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* When using `InterruptExecutor`:
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** disable `executor-thread`
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** make `main`` spawn everything, then enable link:https://docs.rs/cortex-m/latest/cortex_m/peripheral/struct.SCB.html#method.set_sleeponexit[SCB.SLEEPONEXIT] and `loop { cortex_m::asm::wfi() }`
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** *Note:* If you need 2 priority levels, using 2 interrupt executors is better than 1 thread executor + 1 interrupt executor. |