Using J-Link VCOM functionality
Contents
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.
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.
Checking VCOM state
Checking if VCOM is active can be done by opening the device manager.
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.