feat: add Seeed XIAO STM32C5 support by cumin777 · Pull Request #3048 · stm32duino/Arduino_Core_STM32

cumin777 · 2026-08-18T12:00:36Z

Summary

Add Arduino core support for the Seeed XIAO STM32C5.

This PR implements the following features:

Seeed XIAO STM32C5 board variant, pin mapping and linker script
USB CDC Serial support for STM32C5 HAL v2
UF2 upload recipe for the TinyUF2 bootloader
Onboard IMU I2C, interrupt and heater-control pins

The board requires support for the STM32C5 HAL v2 USB device peripheral and
uses a 32 KiB TinyUF2 bootloader, so the application image starts at
0x08008000.

The application USB identity is 2886:80C5. The corresponding bootloader is
maintained separately with identity 2886:00C5.

Automatic upload uses the standard 1200-bps CDC touch flow to enter TinyUF2,
then writes the generated UF2 image to the XIAOC5BOOT mass-storage volume.
The uf2upload executable is supplied by the companion Arduino_Tools PR and
will be consumed through a subsequent STM32Tools release/package-index update.

Validation

Hardware validation was performed on Seeed XIAO STM32C5:

USB CDC enumeration and serial communication
1200-bps touch from a running application, bootloader entry, and full
automatic UF2 upload
SPI3 D9/D10 loopback
I2C scan
External flash access
Onboard LSM6DS3TR-C IMU readout and interrupt handling
IMU heater PWM temperature-control loop

CI and AStyle checks are pending GitHub Actions.

fpistm

Hi @cumin777
thanks for this PR.
It is a first round of review.
Have you any link on the board?

fpistm · 2026-08-18T12:28:22Z

+#define USB USB_DRD_FS
+#define PCD_SNG_BUF HAL_PCD_SNG_BUF
+#define PCD_DBL_BUF HAL_PCD_DBL_BUF


It would be better to add it in the stm32_def.h, other series also redefine some USB definition.

Arduino_Core_STM32/libraries/SrcWrapper/inc/stm32_def.h

Lines 206 to 224 in 36a8f85

/* STM32G0xx, STM32U0xx and some STM32U5xx defined USB_DRD_FS */

#if !defined(USB) && defined(USB_DRD_FS)

#define USB USB_DRD_FS

#define PinMap_USB PinMap_USB_DRD_FS

#if defined(STM32H5xx) || defined(STM32U0xx) ||\

defined(STM32U3xx) || defined(STM32U5xx)

#define USB_BASE USB_DRD_BASE

#if !defined(__HAL_RCC_USB_CLK_ENABLE)

#if defined(__HAL_RCC_USB_FS_CLK_ENABLE)

#define __HAL_RCC_USB_CLK_ENABLE __HAL_RCC_USB_FS_CLK_ENABLE

#define __HAL_RCC_USB_CLK_DISABLE __HAL_RCC_USB_FS_CLK_DISABLE

#endif

#if defined(__HAL_RCC_USB1_CLK_ENABLE)

#define __HAL_RCC_USB_CLK_ENABLE __HAL_RCC_USB1_CLK_ENABLE

#define __HAL_RCC_USB_CLK_DISABLE __HAL_RCC_USB1_CLK_DISABLE

#endif

#endif

#endif

#endif

USB_BASE should also be defined.

fpistm · 2026-08-18T12:29:36Z

+#define USB_IRQn USB_DRD_FS_IRQn
+#define USB_IRQHandler USB_DRD_FS_IRQHandler


When USB_BASE defined simply add STM32C5xx in the list:

Arduino_Core_STM32/libraries/USBDevice/inc/usbd_conf.h

Line 80 in 36a8f85

#elif defined(STM32C0xx) || defined(STM32H5xx) || defined(STM32U0xx)

fpistm · 2026-08-18T12:31:17Z

I think it should be renamed to a more generic name like: usbd_confv2.c

fpistm · 2026-08-18T12:31:38Z

@@ -0,0 +1,251 @@
+/**
+  ******************************************************************************
+  * @file    usbd_conf_c5.c


usbd_confv2.c

fpistm · 2026-08-18T12:32:10Z

+/**
+  ******************************************************************************
+  * @file    usbd_conf_c5.c
+  * @brief   STM32C5 HAL v2 USB device low-level adapter.


Remove STM32C5.

fpistm · 2026-08-18T13:01:23Z

    }

 #if defined(SPI_IFCR_EOTC)
+spi_transfer_end:


I think there is a trap here. For future HALV2 series based. If SPI_IFCR_EOTC is not defined goto will not reach it.

fpistm · 2026-08-18T13:04:50Z

+static bool spi_transfer_timed_out(uint32_t start_us)
+{
+  return (SPI_TRANSFER_TIMEOUT != HAL_MAX_DELAY)
+         && ((uint32_t)(micros() - start_us) >= (SPI_TRANSFER_TIMEOUT * 1000UL));


micros() uses HAL_GetTick() so wonder if your statement is correct?

Arduino_Core_STM32/libraries/SrcWrapper/src/stm32/clock.c

Line 31 in 36a8f85

uint32_t m0 = HAL_GetTick();

fpistm · 2026-08-18T14:33:06Z

+void SPIClass::configSpi(const SPISettings &settings, bool force)
 {
-  if (_spiSettings != settings) {
+  if (force || _spiSettings != settings) {


Interesting.
It seems we introduce a regression when the ArduinoCore-API was released.
Thanks for pointing this. I will provide a fix for this. I don't think adding a new arguments is the better way.

Could you file an issue for this, please?

fpistm · 2026-08-18T14:35:39Z

 #define PIN_SPI_SS2             NUM_DIGITAL_PINS
 #define PIN_SPI_SS3             NUM_DIGITAL_PINS
-#define PIN_SPI_MOSI            PB_15_ALT2
+#define PIN_SPI_MOSI            (PB15 | ALT2)


cumin777 · 2026-08-19T10:57:32Z

Hi @fpistm, thank you for the detailed first review.

The Seeed XIAO STM32C5 is currently in the DVT stage and is planned for public launch in September, so there is no public product page available yet. I will share the official board link once it is published.
I have pushed an update addressing your comments: the USB HAL v2 adapter has been generalized, the USB definitions were moved to the common layer, the board menus now follow the existing core conventions, and the SPI3 MOSI alternate-function name was updated. Could you please check whether this now matches your expectations?
Regarding the SPI initialization regression, I saw that you have opened fix(spi): init never called at begin #3049, which addresses the same root cause. I have removed the board-specific SPI workaround from this PR, so I believe a separate issue is no longer needed. Please let me know if you would still prefer one.

fpistm · 2026-08-19T11:50:50Z

Hi, thanks for the update.
and yes an issue for the SPI would help to track it.

As the board is not yet available. It would be fine to keep here only the board support addition and open separate PR for specific feature. I will try on my side and a Nucleo C562RE

cumin777 · 2026-08-20T08:03:36Z

Hi @fpistm, understood. I will open an issue for this.

Although the board does not yet have a public product page, I can provide test reports to demonstrate the product and its validation status. Our product manager is working to ensure Arduino platform support is ready as early as possible for our users.

If helpful, I would be glad to share this information with you. The current planned public launch date is August 29.

Thank you very much for your support.

cumin777 · 2026-08-20T08:05:40Z

I also noticed that the CI workflows for the latest update are awaiting approval. Could you please approve them when convenient, so the checks can run? :)

fpistm · 2026-08-20T13:54:19Z

Thanks for the update. Will check this tomorrow.

cumin777 added 13 commits August 10, 2026 15:55

fix(halv2): adapt UART reset and IRQ helpers

def9340

feat(usb): add C5 HAL v2 CDC support

dc3313b

feat(usb): add optional CDC line-coding hook

da8a904

feat(upload): add generic UF2 uploader recipe

6d7eeb2

feat(xiao): add STM32C5 board variant

af81304

feat(xiao): enable SPI3 pin mapping

f326cf1

fix(spi): bound HAL v2 polling transfers

58dbf25

fix(spi): initialize bus on begin

89bbefa

fix(xiao): select SPI3 alternate function for MOSI

e1884f2

fix(usb): limit CDC transmit blocks to packet size

178420b

fix(usb): use non-overlapping C5 CDC PMA buffers

73e186f

fix(xiao): keep SPI3 MOSI in board pin namespace

1211767

feat(xiao): expose onboard IMU control pins

69d48fe

fpistm requested changes Aug 18, 2026

View reviewed changes

cumin777 added 4 commits August 19, 2026 14:07

fix(usb): generalize HAL v2 device adapter

f084faa

fix(xiao): align board menus with core conventions

80f14e8

fix(xiao): name SPI3 MOSI alternate function

4b38d5a

revert(spi): drop board-specific workarounds

b9e53e9

cumin777 force-pushed the feat/xiao-stm32c5 branch from c6bd5f4 to b9e53e9 Compare August 19, 2026 06:08

	/* STM32G0xx, STM32U0xx and some STM32U5xx defined USB_DRD_FS */
	#if !defined(USB) && defined(USB_DRD_FS)
	#define USB USB_DRD_FS
	#define PinMap_USB PinMap_USB_DRD_FS
	#if defined(STM32H5xx) \|\| defined(STM32U0xx) \|\|\
	defined(STM32U3xx) \|\| defined(STM32U5xx)
	#define USB_BASE USB_DRD_BASE
	#if !defined(__HAL_RCC_USB_CLK_ENABLE)
	#if defined(__HAL_RCC_USB_FS_CLK_ENABLE)
	#define __HAL_RCC_USB_CLK_ENABLE __HAL_RCC_USB_FS_CLK_ENABLE
	#define __HAL_RCC_USB_CLK_DISABLE __HAL_RCC_USB_FS_CLK_DISABLE
	#endif
	#if defined(__HAL_RCC_USB1_CLK_ENABLE)
	#define __HAL_RCC_USB_CLK_ENABLE __HAL_RCC_USB1_CLK_ENABLE
	#define __HAL_RCC_USB_CLK_DISABLE __HAL_RCC_USB1_CLK_DISABLE
	#endif
	#endif
	#endif
	#endif

		#define USB_IRQn USB_DRD_FS_IRQn
		#define USB_IRQHandler USB_DRD_FS_IRQHandler

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cumin777 commented Aug 18, 2026

Summary

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cumin777 commented Aug 19, 2026

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fpistm commented Aug 19, 2026

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cumin777 commented Aug 20, 2026

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cumin777 commented Aug 20, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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cumin777 commented Aug 20, 2026 •

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