Chapter 4
On-board (Link2) debug probe
This section describes the features provided by the on-board Link2 Debug Probe, including how to use this to debug an external
target.
The Link2 Debug Probe is implemented using an LPC43xx MCU, which provides a high-speed USB port interface to the host
computer that runs the development tools. This device is not intended for developer use and should only be used with approved
firmware images from NXP. The Link2 on-chip flash memory is factory programmed with a firmware image that supports CMSIS-
DAP debug protocol, but also includes other USB end point functions.
• Virtual COM (VCOM) port: a serial device that can be used with any host computer application design for serial port
communication (e.g. Teraterm, puTTY, etc.). Set the terminal program for baud rate to 115200, no parity, 8 bit data, 1 stop
bit, no flow control.
• SWO trace end point: this virtual device is used by MCUXpresso to retrieve SWO trace data. See the MCUXpresso IDE
documentation for more information.
• I2C/SPI bridges: bridge device from I2C and SPI ports of the MCU target.
All of these devices are independent of each other and of the CMSIS-DAP debug device that is enumerated when the board is
connected to a host computer; for example, the VCOM port can be used if the board is running an application when no debugger
is running.
In order to correctly install and use the Link2 device on the i.MX RT685 EVK (required for any debugging purpose) for Windows
7 (or later) host computers, install the drivers first. These drivers will automatically be installed when MCUXpresso IDE has already
been installed. If these IDEs are not being used, it is recommended LPCScrypt be installed as this also includes the required
drivers. All these tools and utilities are available for free download at
.
The CMSIS-DAP firmware image installed at the factory (and by LPCScrypt) will uniquely identify itself to the host computer so
that more than one board can be connected to that host computer at any time. Some toolchains cannot discern between multiple
debug devices. Refer to your toolchain documentation for more information.
The MCUXpresso does support multiple LPCXpresso board targets. It is strongly recommended that LPCScrypt be used to update
the Debug Probe firmware in order to ensure the latest version is being used.
The Link2 only boots when the board is power cycled. The reset button on the board does not reset the Link2.
NOTE
When using MCUXpresso IDE, the Link2 can be automatically booted with the latest/most appropriate firmware for that IDE
version by installing JP1 DFU jumper before powering up the board. This is the recommended approach for the MCUXpresso IDE.
If JP1 is installed when powering the board then the VCOM port (and other devices mentioned above) device will not appear until
the MCUXpresso IDE boots the Debug Probe. The Debug Probe is booted once a debug session is started (that is, the IDE
attempts to download code to the target).
4.1 Programming the Link2 firmware
As mentioned earlier in this section, it is not normally necessary to program the Link2 firmware. However, this can easily be
accomplished using the supporting utility, LPCScrypt.
To program the Link2 Flash the Link2 device (LPC432x) must be in DFU mode. If the Link2 already has a valid image in the flash,
it will need to be forced into DFU mode by placing a jumper shunt on JP1, and power cycling (disconnecting then reconnecting
power). Link2 MCU programming is performed using the LPCScrypt utility (see
). Instructions for
using the tool are located at the same web page.
NXP Semiconductors
i.MX RT685 Evaluation Board, Rev. 0, March 20 2020
User's Guide
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