[ABANDONED] VCOM on Jlink EDU v9.40

pbljung · Mar 4th 2017, 3:34am

I enabled VCOM on a Segger Jlink EDU v9.40 which results in a Segger CDC as COM4 on my windows computer, but I don't see any RX or TX activity on Putty or Terminal. How do I get VCOM to work? (Downloading and RTT works fine.)

I *do* see RX and TX when using a logic analyzer connected to pins 5 and 15 on the Jlink. I also see RX and TX in Terminal on COM7 using a FTDI adapter connected to these same pins.

SEGGER - Niklas · Mar 6th 2017, 10:39am

Hi,

I *do* see RX and TX when using a logic analyzer connected to pins 5 and 15 on the Jlink.

According to UM8001, the pins used for VCOM are 5 and 17, not 5 and 15:

Does it work for you when using pin 17 instead of 15?

Best regards,
Niklas

pbljung · Mar 7th 2017, 10:27pm

My mistake not looking at the pin numbers. I can see RX and TX on pins 5 & 15 using a logic analyzer, but nothing on the Segger created port. How do I get VCOM working?

SEGGER - Niklas · Mar 20th 2017, 10:06am

Hi,

sorry for the delay in response.
As mentioned in the screenshot, you need to use pin 5 /17 and it only works when using the SWD interface.
In order to test proper VCOM function of the J-Link, I would recommend to disconnect the J-Link from any target, and measuring pin 5/17 on the J-Link interface while sending out characters with a pc application (e.g. putty) via the J-Link COM-Port.
Furthermore, you could create a local loop back by connecting pin 5 and pin 17 of the J-Link interface, which can be verified again with an application like putty.

Best regards,
Niklas

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