Debug Probes

A debug probe is special hardware which allows you to control execution of a Zephyr application running on a separate board. Debug probes usually allow reading and writing registers and memory, and support breakpoint debugging of the Zephyr application on your host workstation using tools like GDB. They may also support other debug software and more advanced features such as tracing program execution. For details on the related host software supported by Zephyr, see Flash & Debug Host Tools.

Debug probes are usually connected to your host workstation via USB; they are sometimes also accessible via an IP network or other means. They usually connect to the device running Zephyr using the JTAG or SWD protocols. Debug probes are either separate hardware devices or circuitry integrated into the same board which runs Zephyr.

Many supported boards in Zephyr include a second microcontroller that serves as an onboard debug probe, usb-to-serial adapter, and sometimes a drag-and-drop flash programmer. This eliminates the need to purchase an external debug probe and provides a variety of debug host tool options.

Several hardware vendors have their own branded onboard debug probe implementations: NXP LPC boards have LPC-Link2, NXP Kinetis (former Freescale) boards have OpenSDA, and ST boards have ST-LINK. Each onboard debug probe microcontroller can support one or more types of firmware that communicate with their respective debug host tools. For example, an OpenSDA microcontroller can be programmed with DAPLink firmware to communicate with pyOCD or OpenOCD debug host tools, or with J-Link firmware to communicate with J-Link debug host tools.

Debug Probes & Host Tools Compatibility Chart		Host Tools
Debug Probes & Host Tools Compatibility Chart		J-Link Debug	OpenOCD	pyOCD	NXP S32DS
Debug Probes	LPC-Link2 J-Link	✓
	OpenSDA DAPLink		✓	✓
	OpenSDA J-Link	✓
	J-Link External	✓	✓
	ST-LINK/V2-1	✓	✓	some STM32 boards
	NXP S32 Debug Probe				✓

Some supported boards in Zephyr do not include an onboard debug probe and therefore require an external debug probe. In addition, boards that do include an onboard debug probe often also have an SWD or JTAG header to enable the use of an external debug probe instead. One reason this may be useful is that the onboard debug probe may have limitations, such as lack of support for advanced debuggers or high-speed tracing. You may need to adjust jumpers to prevent the onboard debug probe from interfering with the external debug probe.

MCU-Link CMSIS-DAP Onboard Debug Probe

The CMSIS-DAP debug probes allow debugging from any compatible toolchain, including IAR EWARM, Keil MDK, NXP’s MCUXpresso IDE and MCUXpresso extension for VS Code. In addition to debug probe functionality, the MCU-Link probes may also provide:

SWO trace end point: this virtual device is used by MCUXpresso to retrieve SWO trace data. See the MCUXpresso IDE documentation for more information.
Virtual COM (VCOM) port / UART bridge connected to the target processor
USB to UART, SPI and/or I2C interfaces (depending on MCU-Link type/implementation)
Energy measurements of the target MCU

This debug probe is compatible with the following debug host tools:

LinkServer Debug Host Tools

This probe is realized by programming the MCU-Link microcontroller with the CMSIS-DAP MCU-Link firmware, which is already installed by default. NXP recommends using NXP’s MCUXpresso Installer, which installs both the MCU-Link host tools plus the LinkServer Debug Host Tools.

Put the MCU-Link microcontroller into DFU boot mode by attaching the DFU jumper, then powering up the board.
Run the program_CMSIS script, found in the installed MCU-Link scripts folder.
Remove the DFU jumper and power cycle the board.

MCU-Link JLink Onboard Debug Probe

The MCU-Link J-Link is an onboard debug probe and usb-to-serial adapter supported on many NXP development boards.

This debug probe is compatible with the following debug host tools:

J-Link Debug Host Tools

These probes do not have JLink firmware installed by default, and must be updated. NXP recommends using NXP’s MCUXpresso Installer, which installs both the J-Link Debug Host Tools plus the MCU-Link host tools.

Put the MCU-Link microcontroller into DFU boot mode by attaching the DFU jumper, then powering up the board.
Run the program_JLINK script, found in the installed MCU-Link scripts folder.
Remove the DFU jumper and power cycle the board.

LPC-LINK2 CMSIS DAP Onboard Debug Probe

The CMSIS-DAP debug probes allow debugging from any compatible toolchain, including IAR EWARM, Keil MDK, as well as NXP’s MCUXpresso IDE and MCUXpresso extension for VS Code. As well as providing debug probe functionality, the LPC-Link2 probes also provide:

SWO trace end point: this virtual device is used by MCUXpresso to retrieve SWO trace data. See the MCUXpresso IDE documentation for more information.
Virtual COM (VCOM) port / UART bridge connected to the target processor
LPCSIO bridge that provides communication to I2C and SPI slave devices

This probe is realized by programming the LPC-Link2 microcontroller with the CMSIS-DAP LPC-Link2 firmware. Download and install LPCScrypt to get the firmware and programming scripts.

Note

Verify the firmware supports your board by visiting Firmware for LPCXpresso

Put the LPC-Link2 microcontroller into DFU boot mode by attaching the DFU jumper, then powering up the board.
Run the program_CMSIS script.
Remove the DFU jumper and power cycle the board.

LPC-Link2 J-Link Onboard Debug Probe

The LPC-Link2 J-Link is an onboard debug probe and usb-to-serial adapter supported on many NXP LPC and i.MX RT development boards.

This debug probe is compatible with the following debug host tools:

J-Link Debug Host Tools

This probe is realized by programming the LPC-Link2 microcontroller with J-Link LPC-Link2 firmware. Download and install LPCScrypt to get the firmware and programming scripts.

Note

Verify the firmware supports your board by visiting Firmware for LPCXpresso

Put the LPC-Link2 microcontroller into DFU boot mode by attaching the DFU jumper, then powering up the board.
Run the program_JLINK script.
Remove the DFU jumper and power cycle the board.

OpenSDA DAPLink Onboard Debug Probe

The OpenSDA DAPLink is an onboard debug probe and usb-to-serial adapter supported on many NXP Kinetis and i.MX RT development boards. It also includes drag-and-drop flash programming support.

This debug probe is compatible with the following debug host tools:

This probe is realized by programming the OpenSDA microcontroller with DAPLink OpenSDA firmware. NXP provides OpenSDA DAPLink Board-Specific Firmwares.

Install the debug host tools before you program the firmware.

As with all OpenSDA debug probes, the steps for programming the firmware are:

Put the OpenSDA microcontroller into bootloader mode by holding the reset button while you power on the board. Note that “bootloader mode” in this context applies to the OpenSDA microcontroller itself, not the target microcontroller of your Zephyr application.
After you power on the board, release the reset button. A USB mass storage device called BOOTLOADER or MAINTENANCE will enumerate.
Copy the OpenSDA firmware binary to the USB mass storage device.
Power cycle the board, this time without holding the reset button. You should see three USB devices enumerate: a CDC device (serial port), a HID device (debug port), and a mass storage device (drag-and-drop flash programming).

OpenSDA J-Link Onboard Debug Probe

The OpenSDA J-Link is an onboard debug probe and usb-to-serial adapter supported on many NXP Kinetis and i.MX RT development boards.

This debug probe is compatible with the following debug host tools:

J-Link Debug Host Tools

This probe is realized by programming the OpenSDA microcontroller with J-Link OpenSDA firmware. Segger provides OpenSDA J-Link Generic Firmwares and OpenSDA J-Link Board-Specific Firmwares, where the latter is generally recommended when available. Board-specific firmwares are required for i.MX RT boards to support their external flash memories, whereas generic firmwares are compatible with all Kinetis boards.

Install the debug host tools before you program the firmware.

As with all OpenSDA debug probes, the steps for programming the firmware are:

Put the OpenSDA microcontroller into bootloader mode by holding the reset button while you power on the board. Note that “bootloader mode” in this context applies to the OpenSDA microcontroller itself, not the target microcontroller of your Zephyr application.
After you power on the board, release the reset button. A USB mass storage device called BOOTLOADER or MAINTENANCE will enumerate.
Copy the OpenSDA firmware binary to the USB mass storage device.
Power cycle the board, this time without holding the reset button. You should see two USB devices enumerate: a CDC device (serial port) and a vendor-specific device (debug port).

J-Link External Debug Probe

Segger J-Link is a family of external debug probes, including J-Link EDU, J-Link PLUS, J-Link ULTRA+, and J-Link PRO, that support a large number of devices from different hardware architectures and vendors.

This debug probe is compatible with the following debug host tools:

Install the debug host tools before you program the firmware.

ST-LINK/V2-1 Onboard Debug Probe

ST-LINK/V2-1 is a serial and debug adapter built into all Nucleo and Discovery boards. It provides a bridge between your computer (or other USB host) and the embedded target processor, which can be used for debugging, flash programming, and serial communication, all over a simple USB cable.

It is compatible with the following host debug tools:

For some STM32 based boards, it is also compatible with:

pyOCD Debug Host Tools

While it works out of the box with OpenOCD, it requires some flashing to work with J-Link. To do this, SEGGER offers a firmware upgrading the ST-LINK/V2-1 on board on the Nucleo and Discovery boards. This firmware makes the ST-LINK/V2-1 compatible with J-LinkOB, allowing users to take advantage of most J-Link features like the ultra fast flash download and debugging speed or the free-to-use GDBServer.

More information about upgrading ST-LINK/V2-1 to JLink or restore ST-Link/V2-1 firmware please visit: Segger over ST-Link

Flash and debug with ST-Link

OpenOCD is available by default on ST-Link and configured as the default flash and debug tool. Flash and debug can be done as follows:

# From the root of the zephyr repository
west build -b None samples/hello_world
west flash

# From the root of the zephyr repository
west build -b None samples/hello_world
west debug

Once STLink is flashed with SEGGER FW and J-Link GDB server is installed on your host computer, you can flash and debug as follows:

Use CMake with -DBOARD_FLASH_RUNNER=jlink to change the default OpenOCD runner to J-Link. Alternatively, you might add the following line to your application CMakeList.txt file.

set(BOARD_FLASH_RUNNER jlink)

If you use West (Zephyr’s meta-tool) you can modify the default runner using the --runner (or -r) option.

west flash --runner jlink

To attach a debugger to your board and open up a debug console with jlink.

west debug --runner jlink

For more information about West and available options, see West (Zephyr’s meta-tool).

If you configured your Zephyr application to use Segger RTT console instead, open telnet:

$ telnet localhost 19021
Trying ::1...
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
SEGGER J-Link V6.30f - Real time terminal output
J-Link STLink V21 compiled Jun 26 2017 10:35:16 V1.0, SN=773895351
Process: JLinkGDBServerCLExe
Zephyr Shell, Zephyr version: 1.12.99
Type 'help' for a list of available commands
shell>

If you get no RTT output you might need to disable other consoles which conflict with the RTT one if they are enabled by default in the particular sample or application you are running, such as disable UART_CONSOLE in menuconfig

Updating or restoring ST-Link firmware

ST-Link firmware can be updated using STM32CubeProgrammer Tool. It is usually useful when facing flashing issues, for instance when using twister’s device-testing option.

Once installed, you can update attached board ST-Link firmware with the following command

s java -jar ~/STMicroelectronics/STM32Cube/STM32CubeProgrammer/Drivers/FirmwareUpgrade/STLinkUpgrade.jar -sn <board_uid>

Where board_uid can be obtained using twister’s generate-hardware-map option. For more information about twister and available options, see Test Runner (Twister).

NXP S32 Debug Probe

NXP S32 Debug Probe enables NXP S32 target system debugging via a standard debug port while connected to a developer’s workstation via USB or remotely via Ethernet.

NXP S32 Debug Probe is designed to work in conjunction with NXP S32 Design Studio (S32DS) and NXP Automotive microcontrollers and processors. Install the debug host tools as in indicated in NXP S32 Debug Probe Host Tools before you program the firmware.