Using J-Link VCOM functionality

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Enabling VCOM

In general, the VCOM feature can be disabled and enabled for debug probes which comes with support for it via J-Link Commander and J-Link Configurator. Note that VCOM can only be used when debugging via SWD target interface. Pin 5 = J-Link-Tx (out), Pin 17 = J-Link-Rx (in). Currently, only J-Link models with hardware version 9 or newer come with VCOM capabilities.

Via J-Link Configurator

Start the J-Link Configurator and configure the device to enable VCOM functionality by double-clicking. Under 'Virtual COM-Port', choose 'Enable' and click 'OK'. After that the device needs to be power cycled in order for VCOM to work.
VCOM Configurator.png

Via J-Link Commander

Start the J-Link Commander and enter 'vcom enable'. After that the device needs to be power cycled in order for VCOM to work.
VCOM Commander.png

Checking VCOM state

Checking if VCOM is active can be done by opening the device manager. Connected devices with VCOM functionality will be listed under 'Ports (COM & LPT)'.
VCOM DeviceManager.jpg

Testing VCOM functionality

The VCOM functionality can be tested for by simply connecting the Tx pin with the Rx pin - creating a loopback that way - and starting a terminal application. This leads to the Rx pin receiving the sent data meaning that VCOM is active and working.

Checking VCOM speed

The speed at which VCOM is operating at can be checked by using an oscilloscope to measure the Tx signal. This can be done by sending the letter 'U' as it translates to 01010101 in binary, creating a regular square-wave signal.