cpu/stm32: add initial STM32U3 and nucleo-u385rg-q support by itsadarshnair · Pull Request #22175 · RIOT-OS/RIOT

itsadarshnair · 2026-04-05T17:46:08Z

Contribution description

This PR adds initial support for the STM32U3 family and the NUCLEO-U385RG-Q board.

It includes:

initial STM32U3 CPU family support under cpu/stm32
board support for boards/nucleo-u385rg-q
basic clock and peripheral configuration required for bring-up

At the moment, this is an initial bring-up PR. The board boots and the LED blinking example was verified on hardware. Other peripherals and features may still be incomplete or untested.

At this stage, OpenOCD flashing support is not yet available. The board was programmed using STM32CubeProgrammer.

Testing procedure

The changes were tested with the examples/basic/blinky application on the nucleo-u385rg-q board.

Build:
bash
make -C examples/basic/blinky BOARD=nucleo-u385rg-q

Issues/PRs references

Progress for Tracking Issue #19264.

Declaration of AI-Tools / LLMs usage:

AI-Tools / LLMs that were used are:

ChatGPT for understanding the porting process, code generation/suggestions, with user review
Gemini for understanding the porting process and code suggestions, with user review

crasbe

Thank you for creating the Pull Request with the STM32U3 support.

This is the first review round that is has mostly style related comments. I will do a second round once everything style-wise is in order.

There are merge conflicts that have to be resolved before this can be merged.

riot-ci · 2026-04-06T21:00:54Z

Murdock results

✔️ PASSED

79ac4a4 cpu/stm32: select VCORE voltage range 1 on STM32U3 Fixing flashpage test issue

Success	Failures	Total	Runtime
11123	0	11124	14m:18s

Artifacts

Documentation preview

crasbe

Please run dist/tools/compile_and_test_for_board/compile_and_test_for_board.py . nucleo-u385rg-q on your local computer. There are still a lot of compilation errors from missing definitions. Unfortunately that does not show in our CI because the newly added board is not in the quickbuild list.

…nd 'FLASH_CR_PNB' compilation errors.

- Implemented dynamic SYSCLK selection based on board configuration macros (HSI, MSI, HSE) instead of hardcoding HSI16. - Removed dead PLL configuration logic, as STM32U3 natively reaches high frequencies via the MSI oscillator. - Connected the FLASH_WAITSTATES macro to the ACR register to prevent HardFaults at higher frequencies. - Removed initial bring-up notes and professionalized comments to meet upstream production standards.

crasbe

The tests/periph/vbat does not show the correct voltage. It should show 3.3V

main(): This is RIOT! (Version: 2026.07-devel-306-ge119e-stm32u385-port)

RIOT backup battery monitoring test

This test will sample the backup battery once a second


VBAT: 2823[mV]
VBAT: 2830[mV]
VBAT: 2833[mV]
VBAT: 2833[mV]
VBAT: 2830[mV]
VBAT: 2830[mV]
VBAT: 2830[mV]
VBAT: 2833[mV]
VBAT: 2830[mV]
VBAT: 2830[mV]
...

The tests/periph/i2c test hangs when trying to access the bus:

main(): This is RIOT! (Version: 2026.07-devel-306-ge119e-stm32u385-port)<\n>
Start: Test for the low-level I2C driver<\n>
> i2c_scan 0<\r><\n>
Scanning I2C device 0...<\n>
addr not ack'ed = "-", addr ack'ed = "X", addr reserved = "R", error = "E"<\n>
     0 1 2 3 4 5 6 7 8 9 a b c d e f<\n>
0x00 R R R R R R R R

I used the tests/drivers/mcp23x17 test to test the SPI bus and it does not seem to work. Did you test the SPI bus?

The tests/periph/flashpage does not work:

main(): This is RIOT! (Version: 2026.07-devel-306-ge119e-stm32u385-port)
ROM flash read write test

Please refer to the README.md for further information

Flash start addr: 0x08000000
Page size: 4096
Number of pages: 256
> test 0
error verifying the content of page 0
>

The tests/periph/rtc test appears to work.
The tests/periph/hwrng test appears to work.
The tests/periph/pm test appears to work.

crasbe · 2026-05-28T13:14:31Z

+    { .pin = GPIO_PIN(PORT_A, 0), .dev = 0, .chan = 5 },   /* A0  ADC1_IN5  */
+    { .pin = GPIO_PIN(PORT_A, 1), .dev = 0, .chan = 6 },   /* A1  ADC1_IN6  */
+    { .pin = GPIO_PIN(PORT_A, 4), .dev = 0, .chan = 9 },   /* A2  ADC1_IN9  */
+    { .pin = GPIO_PIN(PORT_B, 0), .dev = 0, .chan = 15 },  /* A3  ADC1_IN15 */


These channels do not appear to work. Briding the A0-A3 channels to 3.3V does not change the reading from tests/periph/adc.

crasbe · 2026-05-28T13:15:30Z

+/** @} */
+
+/**
+ * @name    USB device (USB DRD FS) configuration


Did you test the USB peripheral?

… to 256KiB

…test issue

itsadarshnair requested review from MrKevinWeiss, aabadie, jia200x, kaspar030, leandrolanzieri and vincent-d as code owners April 5, 2026 17:46

github-actions Bot added Platform: ARM Platform: This PR/issue effects ARM-based platforms Area: doc Area: Documentation Area: build system Area: Build system Area: boards Area: Board ports Area: cpu Area: CPU/MCU ports Area: Kconfig Area: Kconfig integration labels Apr 5, 2026

crasbe added Type: new feature The issue requests / The PR implemements a new feature for RIOT State: needs rebase State: The codebase was changed since the creation of the PR, making a rebase necessary labels Apr 5, 2026

crasbe reviewed Apr 5, 2026

View reviewed changes

crasbe reviewed Apr 6, 2026

View reviewed changes

Comment thread boards/nucleo-u385rg-q/include/periph_conf.h Outdated

itsadarshnair force-pushed the stm32u385-port branch from 4072c14 to ca4fb00 Compare April 6, 2026 17:58

crasbe added CI: ready for build If set, CI server will compile all applications for all available boards for the labeled PR and removed State: needs rebase State: The codebase was changed since the creation of the PR, making a rebase necessary labels Apr 6, 2026

crasbe self-assigned this Apr 8, 2026

crasbe reviewed Apr 13, 2026

View reviewed changes

Comment thread cpu/stm32/stmclk/stmclk_u3.c Outdated

Comment thread cpu/stm32/stmclk/stmclk_u3.c Outdated

Comment thread cpu/stm32/stmclk/stmclk_u3.c

Comment thread cpu/stm32/kconfigs/u3/Kconfig.lines

crasbe mentioned this pull request May 13, 2026

rust/cpu: Set value for cortex-m33 #22289

Open

Adarsh Nair Mullachery added 5 commits May 21, 2026 17:07

successfull make but not flashing

d45e92e

Fixed LED and Button

7a35e83

Makefile update nucleo64

15dc8df

Peripheral config no I2C, PWM

a5e269a

Update U3 BackupRAM support removed

db4a318

Adarsh Nair Mullachery added 16 commits May 21, 2026 17:07

Moving FLASH KEY to flash_common.c

2782568

fix STM32U3 EXTI and SYSCFG in GPIO drivers

1092f85

Add RTC and EXTI register mappings for STM32U3

4be9e46

Fix Flash Peripheral key

9c45c86

cpu/stm32/usbdev_fs: implement USB DRD support for STM32U3 family

2d3b074

Fix EXTI IRQ and APB3 definitions for STM32U3

13dc526

Fix uart_init_lpuart declaration

f51c0c4

fix flash register mapping for STM32U3 resolving the 'FLASH_CR_PER' a…

d6c8b25

…nd 'FLASH_CR_PNB' compilation errors.

I2C Support for stm32u385

1a920dc

SPI support added for stm32u385

bb4cb9d

PWM support added for stm32u385

4971a9a

ADC added support for stm32u385

911eee3

fix LPUART clock routing for STM32U3

3273e39

Whitelists the STM32U3 family in the VBAT peripheral driver

66edf41

Comment fix

5e144f7

itsadarshnair force-pushed the stm32u385-port branch from 11f37e6 to 5e144f7 Compare May 21, 2026 15:09

Adarsh Nair Mullachery added 2 commits May 23, 2026 13:24

Updating ADC and UART peripheral

edebce9

Fix uart issue

e119e6a

crasbe reviewed May 28, 2026

View reviewed changes

Adarsh Nair Mullachery added 2 commits May 30, 2026 20:20

fixup! cpu/stm32u3: address static tests

edc7fcf

fixup! cpu/stm32: fix vbat channel and vrefint for u3

988c14d

itsadarshnair closed this Jun 8, 2026

itsadarshnair reopened this Jun 8, 2026

Adarsh Nair Mullachery added 6 commits June 8, 2026 21:19

cpu/stm32: rename adc_f3_h7.c -> adc_f3_h7_u3.c for U3 support

2f3fd2f

cpu/stm32: Fixed the comment

c0ad208

cpu/stm32: scope U3 RAM_LEN to U375/U385, fix nucleo-u385rg-q doc RAM…

6e53843

… to 256KiB

cpu/stm32: fix SPI last-frame truncation on STM32U3

b9b38c7

cpu/stm32: removing unnecessary comments

4b3a0bb

cpu/stm32: select VCORE voltage range 1 on STM32U3 Fixing flashpage …

79ac4a4

…test issue

Conversation

itsadarshnair commented Apr 5, 2026 • edited by crasbe Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Contribution description

Testing procedure

Issues/PRs references

Declaration of AI-Tools / LLMs usage:

Uh oh!

crasbe left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

riot-ci commented Apr 6, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Murdock results

Artifacts

Uh oh!

crasbe left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

crasbe left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

crasbe May 28, 2026

Choose a reason for hiding this comment

Uh oh!

crasbe May 28, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

itsadarshnair commented Apr 5, 2026 •

edited by crasbe

Loading

riot-ci commented Apr 6, 2026 •

edited

Loading