ST B_U585I_IOT02A Discovery kit


The B_U585I_IOT02A Discovery kit features an ARM Cortex-M33 based STM32U585AI MCU with a wide range of connectivity support and configurations. Here are some highlights of the B_U585I_IOT02A Discovery kit:

  • STM32U585AII6Q microcontroller featuring 2 Mbyte of Flash memory, 786 Kbytes of RAM in UFBGA169 package

  • 512-Mbit octal-SPI Flash memory, 64-Mbit octal-SPI PSRAM, 256-Kbit I2C EEPROM

  • USB FS, Sink and Source power, 2.5 W power capability

  • 802.11 b/g/n compliant Wi-Fi® module from MXCHIP

  • Bluetooth Low Energy from STMicroelectronics

  • MEMS sensors from STMicroelectronics

    • 2 digital microphones

    • Relative humidity and temperature sensor

    • 3-axis magnetometer

    • 3D accelerometer and 3D gyroscope

    • Pressure sensor, 260-1260 hPa absolute digital output barometer

    • Time-of-flight and gesture-detection sensor

    • Ambient-light sensor

  • 2 push-buttons (user and reset)

  • 2 user LEDs

  • Flexible power supply options:
    • ST-LINK/V3

    • USB Vbus

    • External sources

B_U585I_IOT02A Discovery kit

More information about the board can be found at the B U585I IOT02A Discovery kit website.


The STM32U585xx devices are an ultra-low-power microcontrollers family (STM32U5 Series) based on the high-performance Arm|reg| Cortex|reg|-M33 32-bit RISC core. They operate at a frequency of up to 160 MHz.

  • Ultra-low-power with FlexPowerControl (down to 300 nA Standby mode and 19.5 uA/MHz run mode)

  • Core: ARM® 32-bit Cortex® -M33 CPU with TrustZone® and FPU.

  • Performance benchmark:

    • 1.5 DMPIS/MHz (Drystone 2.1)

    • 651 CoreMark® (4.07 CoreMark® /MHZ)

  • Security and cryptography

    • Arm® TrustZone® and securable I/Os memories and peripherals

    • Flexible life cycle scheme with RDP (readout protection) and password protected debug

    • Root of trust thanks to unique boot entry and secure hide protection area (HDP)

    • Secure Firmware Installation thanks to embedded Root Secure Services

    • Secure data storage with hardware unique key (HUK)

    • Secure Firmware Update support with TF-M

    • 2 AES coprocessors including one with DPA resistance

    • Public key accelerator, DPA resistant

    • On-the-fly decryption of Octo-SPI external memories

    • HASH hardware accelerator

    • Active tampers

    • True Random Number Generator NIST SP800-90B compliant

    • 96-bit unique ID

    • 512-byte One-Time Programmable for user data

    • Active tampers

  • Clock management:

    • 4 to 50 MHz crystal oscillator

    • 32 kHz crystal oscillator for RTC (LSE)

    • Internal 16 MHz factory-trimmed RC ( ±1%)

    • Internal low-power 32 kHz RC ( ±5%)

    • 2 internal multispeed 100 kHz to 48 MHz oscillators, including one auto-trimmed by LSE (better than ±0.25 % accuracy)

    • 3 PLLs for system clock, USB, audio, ADC

    • Internal 48 MHz with clock recovery

  • Power management

    • Embedded regulator (LDO)

    • Embedded SMPS step-down converter supporting switch on-the-fly and voltage scaling

  • RTC with HW calendar and calibration

  • Up to 136 fast I/Os, most 5 V-tolerant, up to 14 I/Os with independent supply down to 1.08 V

  • Up to 24 capacitive sensing channels: support touchkey, linear and rotary touch sensors

  • Up to 17 timers and 2 watchdogs

    • 2x 16-bit advanced motor-control

    • 2x 32-bit and 5 x 16-bit general purpose

    • 4x low-power 16-bit timers (available in Stop mode)

    • 2x watchdogs

    • 2x SysTick timer

  • ART accelerator

    • 8-Kbyte instruction cache allowing 0-wait-state execution from Flash and external memories: up to 160 MHz, MPU, 240 DMIPS and DSP

    • 4-Kbyte data cache for external memories

  • Memories

    • 2-Mbyte Flash memory with ECC, 2 banks read-while-write, including 512 Kbytes with 100 kcycles

    • 786-Kbyte SRAM with ECC OFF or 722-Kbyte SRAM including up to 322-Kbyte SRAM with ECC ON

    • External memory interface supporting SRAM, PSRAM, NOR, NAND and FRAM memories

    • 2 Octo-SPI memory interfaces

  • Rich analog peripherals (independent supply)

    • 14-bit ADC 2.5-Msps, resolution up to 16 bits with hardware oversampling

    • 12-bit ADC 2.5-Msps, with hardware oversampling, autonomous in Stop 2 mode

    • 12-bit DAC, low-power sample and hold

    • 2 operational amplifiers with built-in PGA

    • 2 ultra-low-power comparators

  • Up to 22 communication interfaces

    • USB Type-C / USB power delivery controller

    • USB OTG 2.0 full-speed controller

    • 2x SAIs (serial audio interface)

    • 4x I2C FM+(1 Mbit/s), SMBus/PMBus

    • 6x USARTs (ISO 7816, LIN, IrDA, modem)

    • 3x SPIs (5x SPIs with dual OCTOSPI in SPI mode)

    • 1x FDCAN

    • 2x SDMMC interface

    • 16- and 4-channel DMA controllers, functional in Stop mode

    • 1 multi-function digital filter (6 filters)+ 1 audio digital filter with sound-activity detection

  • CRC calculation unit

  • Development support: serial wire debug (SWD), JTAG, Embedded Trace Macrocell™

  • True Random Number Generator (RNG)

  • Graphic features

    • Chrom-ART Accelerator (DMA2D) for enhanced graphic content creation

    • 1 digital camera interface

  • Mathematical co-processor

  • CORDIC for trigonometric functions acceleration

  • FMAC (filter mathematical accelerator)

More information about STM32U585AI can be found here:

Supported Features

The Zephyr b_u585i_iot02a board configuration supports the following hardware features:






nested vector interrupt controller



serial port-polling; serial port-interrupt







RNG | on-chip | True Random number generator

I2C | on-chip | i2c












independent watchdog




The default configuration can be found in the defconfig file:


Zephyr board options

The STM32U585i is an SoC with Cortex-M33 architecture. Zephyr provides support for building for both Secure and Non-Secure firmware.

The BOARD options are summarized below:




For building Secure (or Secure-only) firmware


For building Non-Secure firmware

Here are the instructions to build Zephyr with a non-secure configuration, using tfm_ipc_ sample:

$ west build -b b_u585i_iot02a_ns samples/tfm_integration/tfm_ipc/

Once done, before flashing, you need to first run a generated script that will set platform option bytes config and erase platform (among others, option bit TZEN will be set).

$ ./build/tfm/
$ west flash

Please note that, after having run a TFM sample on the board, you will need to run ./build/tfm/ once more to clean up the board from secure options and get back the platform back to a “normal” state and be able to run usual, non-TFM, binaries. Also note that, even then, TZEN will remain set, and you will need to use STM32CubeProgrammer to disable it fully, if required.

Connections and IOs

B_U585I_IOT02A Discovery kit has 9 GPIO controllers (from A to I). These controllers are responsible for pin muxing, input/output, pull-up, etc.

For mode details please refer to B U585I IOT02A board User Manual.

Default Zephyr Peripheral Mapping:

  • UART_1 TX/RX : PA9/PA10 (ST-Link Virtual Port Com)

  • LD1 : PH7

  • LD2 : PH6

  • user button : PC13

  • SPI1 NSS/SCK/MISO/MOSI : PE12/P13/P14/P15 (Arduino SPI)

  • I2C_1 SDA/SDL : PB9/PB8 (Arduino I2C)

  • I2C_2 SDA/SDL : PH5/PH4

  • DAC1 CH1 : PA4 (STMOD+1)

  • ADC1_IN15 : PB0

  • USB OTG : PA11/PA12

System Clock

B_U585I_IOT02A Discovery System Clock could be driven by an internal or external oscillator, as well as the main PLL clock. By default the System clock is driven by the PLL clock at 80MHz, driven by 16MHz high speed internal oscillator.

Serial Port

B_U585I_IOT02A Discovery kit has 4 U(S)ARTs. The Zephyr console output is assigned to UART1. Default settings are 115200 8N1.

Programming and Debugging


B_U585I_IOT02A Discovery kit includes an ST-LINK/V2-1 embedded debug tool interface. This interface is supported by the openocd version included in Zephyr SDK.

Flashing an application to B_U585I_IOT02A Discovery kit

Connect the B_U585I_IOT02A Discovery kit to your host computer using the USB port, then run a serial host program to connect with your Discovery board. For example:

$ minicom -D /dev/ttyACM0

Then, build and flash in the usual way. Here is an example for the Hello World application.

# From the root of the zephyr repository
west build -b b_u585i_iot02a samples/hello_world
west flash

You should see the following message on the console:

Hello World! arm



STM32U5 support is not currently supported in openocd. As a temporary workaround, user can use STMicroelectronics customized version of OpenOCD to debug the the B_U585I_IOT02A Discovery kit. For this you need to fetch this repo, checkout branch “openocd-cubeide-r3” and build openocd following the instructions provided in the README of the project. Then, build zephyr project indicating the openocd location in west build command.

Here is an example for the Blinky application.

# From the root of the zephyr repository
west build -b b_u585i_iot02a samples/basic/blinky -- -DOPENOCD="<path_to_openocd>/openocd/src/openocd" -DOPENOCD_DEFAULT_PATH="<path_to_openocd>/openocd/tcl/"

Then, indicate openocd as the chosen runner in flash and debug commands:

$ west flash -r openocd
$ west debug -r openocd