diff --git a/docs/modules/ROOT/pages/faq.adoc b/docs/modules/ROOT/pages/faq.adoc index 6cb7233c1..a074594cc 100644 --- a/docs/modules/ROOT/pages/faq.adoc +++ b/docs/modules/ROOT/pages/faq.adoc @@ -279,6 +279,14 @@ If you see errors that look like this: DMA: error on BDMA@1234ABCD channel 4 ---- -You likely need to set up your linker script to define a special region for this area, and copy data to that region before using with BDMA. +You need to set up your linker script to define a special region for this area, and copy data to that region before using with BDMA. -TODO: show how to do that +General steps: + +1. Find out which memory region BDMA has access to. You can get this information from the bus matrix and the memory mapping table in the STM32 datasheet. +2. Add the memory region to `memory.x`, you can modify the generated one from https://github.com/embassy-rs/stm32-data-generated/tree/main/data/chips. +3. You might need to modify `build.rs` to make cargo pick up the modified `memory.x`. +4. In your code, access the defined memory region using `#[link_section = ".xxx"]` +5. Copy data to that region before using BDMA. + +See link:/examples/stm32h7/src/bin/spi_bdma.rs[this example] for more details. diff --git a/examples/stm32h7/build.rs b/examples/stm32h7/build.rs index 8cd32d7ed..b9bb661f0 100644 --- a/examples/stm32h7/build.rs +++ b/examples/stm32h7/build.rs @@ -1,4 +1,34 @@ +//! This build script copies the `memory.x` file from the crate root into +//! a directory where the linker can always find it at build time. +//! For many projects this is optional, as the linker always searches the +//! project root directory -- wherever `Cargo.toml` is. However, if you +//! are using a workspace or have a more complicated build setup, this +//! build script becomes required. Additionally, by requesting that +//! Cargo re-run the build script whenever `memory.x` is changed, +//! updating `memory.x` ensures a rebuild of the application with the +//! new memory settings. + +use std::env; +use std::fs::File; +use std::io::Write; +use std::path::PathBuf; + fn main() { + // Put `memory.x` in our output directory and ensure it's + // on the linker search path. + let out = &PathBuf::from(env::var_os("OUT_DIR").unwrap()); + File::create(out.join("memory.x")) + .unwrap() + .write_all(include_bytes!("memory.x")) + .unwrap(); + println!("cargo:rustc-link-search={}", out.display()); + + // By default, Cargo will re-run a build script whenever + // any file in the project changes. By specifying `memory.x` + // here, we ensure the build script is only re-run when + // `memory.x` is changed. + println!("cargo:rerun-if-changed=memory.x"); + println!("cargo:rustc-link-arg-bins=--nmagic"); println!("cargo:rustc-link-arg-bins=-Tlink.x"); println!("cargo:rustc-link-arg-bins=-Tdefmt.x"); diff --git a/examples/stm32h7/memory.x b/examples/stm32h7/memory.x new file mode 100644 index 000000000..e5ab1f62c --- /dev/null +++ b/examples/stm32h7/memory.x @@ -0,0 +1,14 @@ +MEMORY +{ + FLASH : ORIGIN = 0x08000000, LENGTH = 2048K /* BANK_1 + BANK_2 */ + RAM : ORIGIN = 0x24000000, LENGTH = 512K /* SRAM */ + RAM_D3 : ORIGIN = 0x38000000, LENGTH = 64K /* SRAM4 */ +} + +SECTIONS +{ + .ram_d3 : + { + *(.ram_d3) + } > RAM_D3 +} \ No newline at end of file diff --git a/examples/stm32h7/src/bin/spi_bdma.rs b/examples/stm32h7/src/bin/spi_bdma.rs new file mode 100644 index 000000000..2fc37fc22 --- /dev/null +++ b/examples/stm32h7/src/bin/spi_bdma.rs @@ -0,0 +1,78 @@ +#![no_std] +#![no_main] + +use core::fmt::Write; +use core::str::from_utf8; + +use cortex_m_rt::entry; +use defmt::*; +use embassy_executor::Executor; +use embassy_stm32::mode::Async; +use embassy_stm32::time::mhz; +use embassy_stm32::{peripherals, spi, Config}; +use heapless::String; +use static_cell::StaticCell; +use {defmt_rtt as _, panic_probe as _}; + +// Defined in memory.x +#[link_section = ".ram_d3"] +static mut RAM_D3: [u8; 64 * 1024] = [0u8; 64 * 1024]; + +#[embassy_executor::task] +async fn main_task(mut spi: spi::Spi<'static, peripherals::SPI6, Async>) { + let read_buffer = unsafe { &mut RAM_D3[0..128] }; + let write_buffer = unsafe { &mut RAM_D3[128..256] }; + + for n in 0u32.. { + let mut write: String<128> = String::new(); + core::write!(&mut write, "Hello DMA World {}!\r\n", n).unwrap(); + let read_buffer = &mut read_buffer[..write.len()]; + let write_buffer = &mut write_buffer[..write.len()]; + // copy data to write_buffer which is located in D3 domain, accessable by BDMA + write_buffer.clone_from_slice(write.as_bytes()); + + spi.transfer(read_buffer, write_buffer).await.ok(); + info!("read via spi+dma: {}", from_utf8(read_buffer).unwrap()); + } +} + +static EXECUTOR: StaticCell = StaticCell::new(); + +#[entry] +fn main() -> ! { + info!("Hello World!"); + + let mut config = Config::default(); + { + use embassy_stm32::rcc::*; + config.rcc.hsi = Some(HSIPrescaler::DIV1); + config.rcc.csi = true; + config.rcc.pll1 = Some(Pll { + source: PllSource::HSI, + prediv: PllPreDiv::DIV4, + mul: PllMul::MUL50, + divp: Some(PllDiv::DIV2), + divq: Some(PllDiv::DIV8), // used by SPI3. 100Mhz. + divr: None, + }); + config.rcc.sys = Sysclk::PLL1_P; // 400 Mhz + config.rcc.ahb_pre = AHBPrescaler::DIV2; // 200 Mhz + config.rcc.apb1_pre = APBPrescaler::DIV2; // 100 Mhz + config.rcc.apb2_pre = APBPrescaler::DIV2; // 100 Mhz + config.rcc.apb3_pre = APBPrescaler::DIV2; // 100 Mhz + config.rcc.apb4_pre = APBPrescaler::DIV2; // 100 Mhz + config.rcc.voltage_scale = VoltageScale::Scale1; + } + let p = embassy_stm32::init(config); + + let mut spi_config = spi::Config::default(); + spi_config.frequency = mhz(1); + + let spi = spi::Spi::new(p.SPI6, p.PA5, p.PA7, p.PA6, p.BDMA_CH1, p.BDMA_CH0, spi_config); + + let executor = EXECUTOR.init(Executor::new()); + + executor.run(|spawner| { + unwrap!(spawner.spawn(main_task(spi))); + }) +}