STLINK/V3MODS VCP loopback test fails with no target attached

[Suti71]

I get no message if i send some bytes about my terminal tool. Because i have no schematic i dont know waht going wrong. Do i need an external supply( target ) or do i need pullup resistor or someone else? A target board isnt still connected.

[TDK]

What are you using to send data? Some terminal programs buffer until a newline is sent or received.

Can you view the TX line using a logic analyzer or scope?

Where and how specifically did you connect the TX and RX pins? Show a picture.

[Andrew Neil]

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@Suti71 wrote:

Do i need an external supply( target ) .

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Quite possibly.

It may well have internal buffers, which are driven or enabled by the Vtarget reference.

 

Just try it!

[Suti71]

I have try out with Realterm and Hterm. I dont belive that we have CR/LF problem. I have a scope - I could check if a signal was transmitted.

 

 

 

[Suti71]

I have connect my osci probe on jumper( soldered bridge ) and Pin 5+7(GND), but nothing happends. Do it works with a target board only? I want to integrate the board into my hardware and therefore wanted to check beforehand whether the UART VCP communication is working. As I see it, I will probably have to connect a target board. I really dislike such incomplete documentation.

 

 

[Suti71]

Or could it be, that on my board( red ) are electronic components missing (see below)?