boards: Added board nucleo_u545re_q by FarhadGUL06 · Pull Request #4803 · tock/tock

FarhadGUL06 · 2026-04-22T09:28:16Z

Pull Request Overview

This pull request adds support for the Nucleo-U545RE-Q board (STM32U545) to Tock OS. It introduces a new stm32u5xx chip crate designed for the ultra-low-power STM32U5 series, with a specific focus on Secure Mode operation and TrustZone compatibility.

Features implemented:

New Chip Crate (stm32u5xx): implementation of core peripherals (RCC, GPIO, EXTI, TIM, USART).
Async USART with DMA: Serial driver using GPDMA engine for background transmission (TX) and IRQs for reliable, low-latency reception (RX) via a 32-byte circular FIFO.
GPIO & EXTI: Fully asynchronous interrupt handling for board buttons and LED.
Alarm HIL: Implemented TIM2 as the timekeeper for both kernel and apps.
Multi-Process Support: Configured for up to 4 simultaneous userspace applications with 64KB+ of sandbox RAM. (Note: Currently tested with 1 app; further multi-app verification is pending tockloader integration).

Testing Strategy

This pull request was tested on a physical Nucleo-U545RE-Q hardware target.

Deployment: Deployment was performed using probe-rs and openocd.
Functionality:
-- Verified kernel boot and console output at 115200 baud via USART1.
-- Verified that the User Button (PC13) triggers asynchronous interrupts to toggle the User LED (PA5).
-- Verified userspace delay_ms functionality using the TIM2-backed Alarm HIL.
-- Validated the GPDMA1 configuration (Request ID 25) for stable background printing.

TODO or Help Wanted

This pull request still needs:

Tockloader Support: Investigating why the OpenOCD stm32u5x target configuration fails to identify the board automatically in WSL environments.
Multi-App Validation: Once tockloader is functional, perform stress tests with multiple concurrent processes to verify the 64KB sandbox allocation.
Extended Peripheral Support: Add more peripherals.

Documentation Updated

No updates required (Follows existing Tock architectural patterns).

Formatting

Ran make prepush.
Ran cargo fmt.

AI Use

The PR description details my use of AI in the production of the code in this PR. This port was developed with the assistance of an AI engineering agent (Gemini CLI). All generated code, register offsets, and memory maps were manually verified against the STM32U545 Reference Manual and validated on live hardware.

bradjc

Looks pretty good, just a couple notes about unsafe.

I'm not sure if it is now, but we really should start using tockloader local-board (if necessary) rather than make/objcopy manual fix ups. Using objcopy makes it nearly impossible to run more than one app. Ideally tockloader just works, but the local-board mechanism is basically just as seemless if there isn't a good way to do partial writes to a chip.

bradjc · 2026-04-22T15:20:15Z

+## Flashing Notes
+
+This board is flashed using **`probe-rs`** or **`openocd`**. Due to the specific 
+memory layout and metadata sections of the STM32U5, the Makefile surgically 
+extracts executable sections (stripping metadata like `.ARM.attributes`) before 
+flashing to prevent errors when writing to protected system memory addresses.


Is the binary file the make system builds not suitable? I would prefer to avoid have custom elf/obcopy logic per-board if we can avoid it. That would seem to suggest the linker script is wrong for this board if it is required, and perhaps we should fix the issue with the linker script so we can document exactly what the requirements are.

@FarhadGUL06 do we have this problem on other boards? Those sections should not be loaded to the board, but I agree with @bradjc that we should rely on the ELF file and not do objcopy.

I have made some changes to tockloader and modified the current Makefile to be similar to the one for the nucleo_f429zi. I also tested installing two apps: a modified version of blink (which blinks the LED every 2 seconds but also toggles the LED when the user button is pressed) and c_hello.

Running "make flash" flashes only the kernel, and "tockloader install --openocd --board nucleo_u545re_q" loads the application from the current folder to the board. An application can also be loaded using "make program" (as explained in the README). Both applications work and can be seen as loaded by using "tockloader list --openocd --board nucleo_u545re_q".

alexandruradovici · 2026-04-27T09:51:01Z

Looks pretty good, just a couple notes about unsafe.

I'm not sure if it is now, but we really should start using tockloader local-board (if necessary) rather than make/objcopy manual fix ups. Using objcopy makes it nearly impossible to run more than one app. Ideally tockloader just works, but the local-board mechanism is basically just as seemless if there isn't a good way to do partial writes to a chip.

I think the flash layout should allow us to use tockloader, meaning it is split in pages of the same size. The manual's section 7.3.1 at page 292 says the flash is spilt up in two banks and has pages of 8KB and that the flash supports read-while-write. We would be able to use directly tockloader as long as we align the kernel and the apps to the 8K page size. I see three possible solutions:

align the kernel and each app to the page size
align the kernel to the page size and rewrite all apps always (tockloader has on option for this) while aligning all apps to the page size
use the local-board and flash the whole flash to the board every time

if read-while-write does not work, we can flash the kernel to bank 0 and the apps to bank 1.

alexandruradovici · 2026-05-06T08:41:48Z

+        }
+    }
+
+    pub fn match_channel(&self, channel: ChannelId) -> Option<usize> {


I suggest implementing From<DmaChannel> for usize and that will allow the use of dam_channel.into().

We can delete this function and just use into.

alexandruradovici

Please use the tock-registers register fields for all the peripherals.

alexandruradovici

Please use the tock-registers register fields for all the peripherals.

FarhadGUL06 · 2026-05-08T12:37:48Z

Hi, @bradjc ! Could you please take a look at my latest commits when you have a moment? Thanks!

bradjc · 2026-05-08T17:31:23Z

+    if let (Some(tx), Some(rx)) = (usart1_channel_tx, usart1_channel_rx) {
+        stm32u545::usart::Usart::set_dma(usart1, dma1, tx, rx);
+    }
+


Can this be moved to Stm32u5xxPeripherals::configure() (or some suitable name)?

Moved all chip wiring to init function from Stm32u5xxDefaultPeripherals

bradjc · 2026-05-08T17:31:45Z

+pub struct Stm32u5xxPeripherals<'a> {
+    pub rcc: rcc::Rcc,
+    pub exti: &'a exti::Exti<'a>,
+    pub dma1: &'a dma::Dma,
+    pub gpio_a: gpio::Port<'a>,
+    pub gpio_c: gpio::Port<'a>,
+    pub usart1: &'a usart::Usart<'a>,
+    pub tim2: tim::Tim2<'a>,
+}


I don't understand why there is this peripherals and the default peripherals.

Stm32u5xxDefaultPeripherals was indeed created to implement InterruptService and Stm32u5xxPeripherals for the board but i see the point and i will combine those.

bradjc · 2026-05-08T17:42:05Z

I really thought I commented this already, but I think we need to include DmaSlice (https://github.com/tock/tock/blob/master/chips/nrf52/src/uart.rs#L166) and PanicWriter (https://github.com/tock/tock/blob/master/chips/nrf52/src/uart.rs#L802) in this PR. It is a bit of bad timing, but otherwise we keep making it more difficult to get to correct/sound chips.

FarhadGUL06 · 2026-05-10T10:02:19Z

Hi @bradjc !
I combined Stm32u5xxPeripherals and Stm32u5xxDefaultPeripherals and implemented DmaSlice.

bradjc · 2026-05-11T15:22:35Z

+    let _ = periphs.usart1.configure(kernel::hil::uart::Parameters {
+        baud_rate: 115200,
+        stop_bits: kernel::hil::uart::StopBits::One,
+        parity: kernel::hil::uart::Parity::None,
+        hw_flow_control: false,
+        width: kernel::hil::uart::Width::Eight,
+    });


I believe this is handled here: https://github.com/tock/tock/blob/master/boards/components/src/console.rs#L97

bradjc · 2026-05-11T15:25:58Z

+/// Writer is used by kernel::debug to print messages to the serial port.
+pub struct Writer {}
+
+/// Global static for debug writer
+#[no_mangle]
+pub static mut WRITER: Writer = Writer {};
+
+impl Write for Writer {
+    fn write_str(&mut self, s: &str) -> core::fmt::Result {
+        self.write(s.as_bytes());
+        Ok(())
+    }
+}
+
+impl IoWrite for Writer {
+    fn write(&mut self, buf: &[u8]) -> usize {
+        let uart = stm32u545::usart::Usart::new(stm32u545::usart::USART1_BASE);
+
+        for &c in buf {
+            uart.transmit_byte(c);
+        }
+        buf.len()
+    }
+}


Suggested change

/// Writer is used by kernel::debug to print messages to the serial port.

pub struct Writer {}

/// Global static for debug writer

#[no_mangle]

pub static mut WRITER: Writer = Writer {};

impl Write for Writer {

fn write_str(&mut self, s: &str) -> core::fmt::Result {

self.write(s.as_bytes());

Ok(())

}

}

impl IoWrite for Writer {

fn write(&mut self, buf: &[u8]) -> usize {

let uart = stm32u545::usart::Usart::new(stm32u545::usart::USART1_BASE);

for &c in buf {

uart.transmit_byte(c);

}

buf.len()

}

}

FarhadGUL06 · 2026-05-11T18:00:31Z

Hi @bradjc ! I've made the final changes you requested. Is there anything else that needs to be changed? If there are any more changes to be made, could you let me know all of them for the current version? I'd like us to get this up and running as soon as possible. Thanks!

github-actions Bot added the stm32 label Apr 22, 2026

bradjc reviewed Apr 22, 2026

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github-actions Bot assigned bradjc Apr 23, 2026

alexandruradovici requested changes Apr 27, 2026

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Comment thread chips/stm32u5xx/src/gpio.rs Outdated

Comment thread chips/stm32u5xx/src/exti.rs Outdated

Comment thread chips/stm32u5xx/src/gpio.rs Outdated

FarhadGUL06 requested a review from alexandruradovici April 27, 2026 12:55

FarhadGUL06 force-pushed the board_nucleo_u545re_q branch from 34b8590 to 07eb27c Compare April 27, 2026 13:31

FarhadGUL06 requested a review from bradjc April 29, 2026 09:12

bradjc reviewed Apr 29, 2026

View reviewed changes

Comment thread chips/stm32u5xx/src/chip.rs Outdated

Comment thread chips/stm32u5xx/src/usart.rs

Comment thread chips/stm32u5xx/src/chip.rs

FarhadGUL06 requested a review from bradjc April 30, 2026 10:32

alexandruradovici requested changes May 6, 2026

View reviewed changes

FarhadGUL06 requested a review from alexandruradovici May 7, 2026 09:32

bradjc reviewed May 8, 2026

View reviewed changes

FarhadGUL06 added 13 commits May 10, 2026 12:08

Initial dummy kernel compile for nucleo_u545re_q

44cbaec

Working usart sending X and led blink

9a730d0

Added working debug!

4bd3b7f

Working tock$

5cac2d6

Added led support

3a24d72

Working app via objcopy

da86206

Working refactored usart

bad5592

Added working usart with arrow

c9f772e

[Button] Not working

58c3084

[Button] Working button, isr 40 -> irq 24

856da6f

Solved warnings

52c91b3

Added DMA only for TX

aa9e645

Tried RX DMA USART

221b1b4

FarhadGUL06 added 23 commits May 10, 2026 12:08

gpio: removed from_u8

310ab6e

Makefile: removed manual stripping steps

62b1611

Makefile: Made it similar to other boards

285ce23

Layout: Removed unnecessary section

2e6684e

README: Documented new Makefile

7d01bf2

Fix CI errors by updating to latest kernel APIs

6d2859e

dma: Added request channel and release channel

919150e

dma: handled all channels irq

ad27e21

dma: added register_bitflields and usart base address

540829c

dma: changed match_channel to use channel.into

fba4e56

dma: changed to setup based on direction

291c12d

exti: Changed to use tock-registers

f8c1d6b

gpio: Changed to use tock-registers

82e0b3c

rcc: Changed to use tock-registers

3242d57

tim: Changed to use tock-registers

a58e724

usart: Changed to use tock-registers

60af8c1

usart: modified one line to use tock-register

898661d

dma: added more tock-registers

98c2704

cargo: removed enum_primitive

6382b4e

Combined Stm32u5xxPeripherals and Stm32u5xxDefaultPeripherals

8c1a243

chips: added init function

4923cc2

io: changed to PanicWriter

42b3ec4

usart: added dmaslice

f64e7b7

FarhadGUL06 force-pushed the board_nucleo_u545re_q branch from 3042c2c to f64e7b7 Compare May 10, 2026 09:56

FarhadGUL06 requested a review from bradjc May 10, 2026 09:56

bradjc reviewed May 11, 2026

View reviewed changes

Removed Writer and usart conf

c883ae9

FarhadGUL06 requested a review from bradjc May 11, 2026 18:01

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FarhadGUL06 commented Apr 22, 2026

Pull Request Overview

Testing Strategy

TODO or Help Wanted

Documentation Updated

Formatting

AI Use

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alexandruradovici commented Apr 27, 2026

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FarhadGUL06 commented May 8, 2026

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bradjc commented May 8, 2026

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FarhadGUL06 commented May 11, 2026

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