ARM V2M Musca B1


The v2m_musca_b1 board configuration is used by Zephyr applications that run on the V2M Musca B1 board. It provides support for the Musca B1 ARM Cortex-M33 CPU and the following devices:

  • Nested Vectored Interrupt Controller (NVIC)
  • System Tick System Clock (SYSTICK)
  • Cortex-M System Design Kit GPIO
  • Cortex-M System Design Kit UART
ARM V2M Musca B1

More information about the board can be found at the V2M Musca B1 Website.


ARM V2M MUSCA B1 provides the following hardware components:

  • ARM Cortex-M33
  • ARM IoT Subsystem for Cortex-M33
  • Memory
    • 512KB on-chip system memory SRAM.
    • 8MB of external QSPI flash.
    • 4MB on-chip boot eFlash.
  • Debug
    • JTAG, SWD & 4 bit TRACE.
    • DAPLink with a virtual UART port.
  • Arduino interface
    • 16 3V3 GPIO.
    • UART.
    • SPI.
    • I2C.
    • I2S.
    • 3-channel PWM.
    • 6-channel analog interface.
  • On-board Peripherals
    • User RGB LED.
    • Gyro sensor.
    • Combined ADC/DAC/temperature sensor.
    • Secure Digital I/O (SDIO) microSD card.

User push buttons

The v2m_musca_b1 board provides the following user push buttons:

  • PBON power on/off.
  • nSRST: Cortex-M33 system reset and CoreSight debug reset.
  • ISP: Updates DAPLink firmware.

Supported Features

The v2m_musca_b1 board configuration supports the following hardware features:

Interface Controller Driver/Component
NVIC on-chip nested vector interrupt controller
SYSTICK on-chip systick
UART on-chip serial port-polling; serial port-interrupt
PINMUX on-chip pinmux
GPIO on-chip gpio
WATCHDOG on-chip watchdog
TIMER on-chip timer

Other hardware features are not currently supported by the port. See the V2M Musca B1 Website for a complete list of V2M Musca board hardware features.

The default configuration can be found in the defconfig file: boards/arm/v2m_musca_b1/v2m_musca_b1_defconfig.

Interrupt Controller

Musca B1 is a Cortex-M33 based SoC and has 15 fixed exceptions and 77 IRQs.

A Cortex-M33-based board uses vectored exceptions. This means each exception calls a handler directly from the vector table.

Zephyr provides handlers for exceptions 1-7, 11, 12, 14, and 15, as listed in the following table:

Exc# Name Remarks Used by Zephyr Kernel
1 Reset   system initialization
2 NMI   system fatal error
3 Hard fault   system fatal error
4 MemManage MPU fault system fatal error
5 Bus   system fatal error
6 Usage fault Undefined instruction, or switch attempt to ARM mode system fatal error
7 SecureFault Unauthorized access to secure region from ns space system fatal error
8 Reserved   not handled
9 Reserved   not handled
10 Reserved   not handled
11 SVC   context switch and software interrupts
12 Debug monitor   system fatal error
13 Reserved   not handled
14 PendSV   context switch
15 SYSTICK   system clock
16 Reserved   not handled
17 Reserved   not handled
18 Reserved   not handled

Pin Mapping

The ARM V2M Musca B1 Board has 4 GPIO controllers. These controllers are responsible for pin-muxing, input/output, pull-up, etc.

All GPIO controller pins are exposed via the following sequence of pin numbers:

  • Pins 0 - 15 are for GPIO

Mapping from the ARM V2M Musca B1 Board pins to GPIO controllers:

  • D0 : P0_0
  • D1 : P0_1
  • D2 : P0_2
  • D3 : P0_3
  • D4 : P0_4
  • D5 : P0_5
  • D6 : P0_6
  • D7 : P0_7
  • D8 : P0_8
  • D9 : P0_9
  • D10 : P0_10
  • D11 : P0_11
  • D12 : P0_12
  • D13 : P0_13
  • D14 : P0_14
  • D15 : P0_15

Peripheral Mapping:

  • UART_0_RX : D0
  • UART_0_TX : D1
  • SPI_0_CS : D10
  • SPI_0_MOSI : D11
  • SPI_0_MISO : D12
  • SPI_0_SCLK : D13
  • I2C_0_SDA : D14
  • I2C_0_SCL : D15

For mode details please refer to Musca B1 Technical Reference Manual (TRM).


Musca B1 has a built-in RGB LED connected to GPIO[4:2] pins.

  • Red LED connected at GPIO[2] pin,with optional PWM0.
  • Green LED connected at GPIO[3] pin,with optional PWM1.
  • Blue LED connected at GPIO[4] pin,with optional PWM2.


The SCC registers select the functions of pins GPIO[4:2].

System Clock

V2M Musca B1 has a 32.768kHz crystal clock. The clock goes to a PLL and is multiplied to drive the Cortex-M33 processors and SSE-200 subsystem. The default is 40MHz but can be increased to 160MHz maximum for the secondary processor (CPU1) via software configuration. The maximum clock frequency for the primary processor (CPU0) is 40MHz.

Serial Port

The ARM Musca B1 processor has two UARTs. Both the UARTs have only two wires for RX/TX and no flow control (CTS/RTS) or FIFO. The Zephyr console output, by default, uses UART1.

Security components

  • Implementation Defined Attribution Unit (IDAU). The IDAU is used to define secure and non-secure memory maps. By default, all of the memory space is defined to be secure accessible only.
  • Secure and Non-secure peripherals via the Peripheral Protection Controller (PPC). Peripherals can be assigned as secure or non-secure accessible.
  • Secure boot.
  • Secure AMBA® interconnect.

Serial Configuration Controller (SCC)

The ARM Musca B1 test chip implements a Serial Configuration Control (SCC) register. The purpose of this register is to allow individual control of clocks, reset-signals and interrupts to peripherals, and pin-muxing.

Boot memory

Normal Musca-B1 test chip boot operation is from 4MB eFlash by default, and it offers the fastest boot method. Musca-B1 test chip also support to boot from 8MB QSPI. You can update the DAPLink firmware for either QSPI or eFlash for booting.

Programming and Debugging

Musca B1 supports the v8m security extension, and by default boots to the secure state.

When building a secure/non-secure application, the secure application will have to set the idau/sau and mpc configuration to permit access from the non-secure application before jumping.

The following system components are required to be properly configured during the secure firmware:

  • AHB5 TrustZone Memory Protection Controller (MPC).
  • AHB5 TrustZone Peripheral Protection Controller (PPC).
  • Implementation-Defined Attribution Unit (IDAU).

For more details please refer to Corelink SSE-200 Subsystem.


Building a secure only application

You can build applications in the usual way. Here is an example for the Hello World application.

# From the root of the zephyr repository
west build -b v2m_musca_b1 samples/hello_world

Open a serial terminal (minicom, putty, etc.) with the following settings:

  • Speed: 115200
  • Data: 8 bits
  • Parity: None
  • Stop bits: 1

Reset the board, and you should see the following message on the corresponding serial port:

Hello World! musca_b1

Building a secure/non-secure with Trusted Firmware

The process requires five steps:

  1. Build Trusted Firmware (tfm).
  2. Import it as a library to the Zephyr source folder.
  3. Build Zephyr with a non-secure configuration.
  4. Merge the two binaries together and sign them.
  5. Concatenate the bootloader with the signed image blob.

In order to build tfm please refer to Trusted Firmware M Guide. Follow the build steps for AN521 target while replacing the platform with -DTARGET_PLATFORM=MUSCA_B1 and compiler (if required) with -DCOMPILER=GNUARM

Copy over tfm as a library to the Zephyr project source and create a shortcut for the secure veneers and necessary header files. All files are in the install folder after TF-M built.

Uploading an application to V2M Musca B1

Applications must be converted to Intel’s hex format before being flashed to a V2M Musca B1. An optional bootloader can be prepended to the image. The QSPI flash base address alias is 0x0, and the eFlash base address alias is 0xA000000. The image offset is calculated by adding the flash offset to the bootloader partition size.

A third-party tool (srecord) is used to generate the Intel formatted hex image. For more information refer to the Srecord Manual.

srec_cat $BIN_BOOLOADER -Binary -offset $FLASH_OFFSET $BIN_SNS -Binary -offset $IMAGE_OFFSET -o $HEX_FLASHABLE -Intel

# For a 128K bootloader IMAGE_OFFSET = $FLASH_OFFSET + 0x20000
srec_cat $BIN_BOOLOADER -Binary -offset 0xA000000 $BIN_SNS -Binary -offset 0xA020000 -o $HEX_FLASHABLE -Intel

Connect the V2M Musca B1 to your host computer using the USB port. You should see a USB connection exposing a Mass Storage (MUSCA_B) and a USB Serial Port. Copy the generated zephyr.hex in the MUSCA_B drive.

Reset the board, and you should see the following message on the corresponding serial port:

Hello World! musca_b1