[ABANDONED] J-Link VCOM (Virtual COM port) at 1.8V ?

awneil · Mar 20th 2020, 9:18pm

Should the J-Link VCOM (Virtual COM port) work at 1.8V ?

I just want to receive stuff from a 1.8V target UART at 115200 baud.

It works OK with an FTDI USB-to-UART cable (1.8V version), but a terminal connected to the J-Link VCOM just shows junk - as if the baud rate were wrong.

SEGGER - Fabian · Mar 27th 2020, 9:57am

Hi,
Thank you for your inquiry.

As always, voltage is referenced from VTref. Please find the VCOM Pinout here:
segger.com/products/debug-probes/j-link/

Please note, that VCOM does not work while using JTAG.

We are not aware of any issues with VCOM.
Could you please confirm the baud rate via an oscilloscope?

For more information please refer to this article:
wiki.segger.com/Using_J-Link_VCOM_functionality

Best regards,
Fabian

awneil · Mar 30th 2020, 11:41pm

Yes, target debug connection is SWD, and VTREF is connected - as it's required by the SWD.

The baud rate looked correct on a scope and, as mentioned, it works fine with an FTDI USB-to-1.8V-UART cable.

I had studied the links provided.

is there any restriction on using the VCOM and SWD simultaneously ?

Target is nRF52 - Cortex-M4

SEGGER - Fabian · Mar 31st 2020, 10:51am

Hi,

awneil wrote:

is there any restriction on using the VCOM and SWD simultaneously ?

no there are no restrictions.

So if you use the FTDI cable, everything works as expected?
Could you tell us what your exact setup is?

Best regards,
Fabian

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