ARM V2M Musca


The v2m_musca board configuration is used by Zephyr applications that run on the V2M Musca board. It provides support for the Musca 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

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


ARM V2M MUSCA provides the following hardware components:

  • ARM Cortex-M33
  • ARM IoT Subsystem for Cortex-M33
  • Memory
    • 128KB SRAM
    • 2MB of external SRAM
    • 8MB of external QSPI flash.
  • 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

User push buttons

The v2m_musca board provides the following user push buttons:

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

Supported Features

The v2m_musca 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 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/v2m_musca_defconfig.

Interrupt Controller

Musca 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 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 0
  • Pins 16 - 31 are for GPIO 1

Mapping from the ARM V2M Musca 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
  • D16 : P1_0
  • D17 : P1_1
  • D18 : P1_2
  • D19 : P1_3
  • D20 : P1_4
  • D21 : P1_5
  • D22 : P1_6
  • D23 : P1_7
  • D24 : P1_8
  • D25 : P1_9
  • D26 : P1_10
  • D27 : P1_11
  • D28 : P1_12
  • D29 : P1_13
  • D30c : P1_14
  • D31 : P1_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_SCL : D14
  • I2C_0_SDA : D15
  • UART_1_RX : D16
  • UART_1_TX : D17
  • SPI_1_CS : D18
  • SPI_1_MOSI : D19
  • SPI_1_MISO : D20
  • SPI_1_SCK : D21
  • I2C_1_SDA : D22
  • I2C_1_SCL : D23

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


Musca 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 PWM0.
  • Blue LED connected at GPIO[4] pin,with optional PWM0.


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

System Clock

V2M Musca 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 50MHz but can be increased to 170MHz maximum for the secondary processor (CPU1) via software configuration. The maximum clock frequency for the primary processor (CPU0) is 50MHz.

Serial Port

The ARM Musca 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 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.

QSPI boot memory

Normal Musca-A test chip boot operation is from external QSPI 8MB flash memory. Only the lowest 256KB of QSPI memory is directly accessible. More memory is accessible through indirect addressing.

Programming and Debugging

Musca 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.

# On Linux/macOS
cd $ZEPHYR_BASE/samples/hello_world
mkdir build && cd build

# On Windows
cd %ZEPHYR_BASE%\samples\hello_world
mkdir build & cd build

# Use cmake to configure a Ninja-based build system:
cmake -GNinja -DBOARD=v2m_musca ..

# Now run ninja on the generated build system:

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! arm

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_A and compiler (if required) with -DCOMPILER=GCC

Copy over tf-m as a library to the zephyr project source and create a shortcut for the secure veneers.

cp -r install/ $ZEPHYR_PROJECT/src/ext
cp $ZEPHYR_PROJECT/src/ext/install/export/tfm/veneers/s_veneers.o $ZEPHYR_PROJECT/src/ext

Build the Zephyr app in the usual way.

Uploading an application to V2M Musca

Applications must be converted to Intel’s hex format before being flashed to a V2M Musca. An optional bootloader can be prepended to the image. The QSPI flash base address alias is 0x200000.

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 $QSPI_FLASH_OFFSET $BIN_SNS -Binary -offset $IMAGE_OFFSET -o $HEX_FLASHABLE -Intel

# For a 64K bootloader IMAGE_OFFSET = $QSPI_FLASH_OFFSET + 0x10000
srec_cat $BIN_BOOLOADER -Binary -offset 0x200000 $BIN_SNS -Binary -offset 0x210000 -o $HEX_FLASHABLE -Intel

# For a 256K bootloader IMAGE_OFFSET = $QSPI_FLASH_OFFSET + 0x40000
srec_cat $BIN_BOOLOADER -Binary -offset 0x200000 $BIN_SNS -Binary -offset 0x240000 -o $HEX_FLASHABLE -Intel

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

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

Hello World! arm