The two generations of the STM32L1 Discovery development boards come with an integrated ST-LINK/V2 debugger and programmer. The boards have a 24-segment LCD and a touch slider, along with two user LEDs and a user button. Support circuitry for measuring power consumption is also available. It also comes with a comprehensive STM32 software HAL library and various packaged software examples.

There are two variants of the board:

  • STM32LDISCOVERY targets STM32L152RBT6, with 128K flash, 16K RAM
  • 32L152CDISCOVERY targets STM32L152RCT6, with 256K flash, 32K RAM

The STM32LDISCOVERY is no longer sold, but was widely available. The current configuration assumes only 128K flash and 16K RAM, so it builds and runs on both variants out of the box.


More information about the board can be found at the STM32LDISCOVERY website [1].


The STM32 Discovery board features:

  • On-board ST-LINK/V2 with selection mode switch to use the kit as a standalone ST-LINK/V2 (with SWD connector for programming and debugging)

  • Board power supply: through USB bus or from an external 5 V supply voltage

  • External application power supply: 3 V and 5 V

  • Four LEDs:

    • LD1 (red) for 3.3 V power on
    • LD2 (red/green) for USB communication
    • LD3 (green) for PC9 output
    • LD4 (blue) for PC8 output
  • Two push buttons (user and reset)

  • Extension header for all LQFP64 I/Os for quick connection to prototyping board and easy probing

More information about STM32L151x can be found in the STM32L1x reference manual [2].

Supported Features

The Zephyr stm32l1_disco board configuration supports the following hardware features:

Supported hardware
Interface Controller Driver/component
NVIC on-chip nested vector interrupt controller
UART on-chip serial port-polling serial port-interrupt
PINMUX on-chip pinmux
GPIO on-chip gpio
CLOCK on-chip reset and clock control
FLASH on-chip flash memory
WATCHDOG on-chip window watchdog
I2C on-chip i2c
SPI on-chip spi

Other hardware features are not yet supported in this Zephyr port.

The default configuration can be found in the defconfig file: boards/arm/stm32l1_disco/stm32l1_disco_defconfig

Connections and IOs

Each of the GPIO pins can be configured by software as output (push-pull or open-drain), as input (with or without pull-up or pull-down), or as peripheral alternate function. Most of the GPIO pins are shared with digital or analog alternate functions. All GPIOs are high current capable except for analog inputs.

Default Zephyr Peripheral Mapping:

  • UART_1_TX : PA9
  • UART_1_RX : PA10
  • UART_2_TX : PA2
  • UART_2_RX : PA3
  • I2C1_SCL : PB6
  • I2C1_SDA : PB7
  • I2C2_SCL : PB10
  • I2C2_SDA : PB11
  • SPI1_NSS : PA4
  • SPI1_SCK : PA5
  • SPI1_MISO : PA6
  • SPI1_MOSI : PA7
  • SPI2_NSS : PB12
  • SPI2_SCK : PB13
  • SPI2_MISO : PB14
  • SPI2_MOSI : PB15

For mode details please refer to STM32L1DISCOVERY board User Manual [3].

Programming and Debugging

Applications for the stm32l1_disco board configuration can be built and flashed in the usual way (see Building an Application and Run an Application for more details).


STM32L1DISCOVERY board includes an ST-LINK/V2 embedded debug tool interface. This interface is supported by the openocd version included in the Zephyr SDK.

Flashing an application

Here is an example for the Blinky Application application.

# From the root of the zephyr repository
west build -b stm32l1_disco samples/basic/blinky
west flash

You will see the LED blinking every second.


You can debug an application in the usual way. Here is an example for the Blinky Application application.

# From the root of the zephyr repository
west build -b stm32l1_disco samples/basic/blinky
west debug