Virtual com Port on Windows7 Guest

[MJH]

Hi

We're using Nordic Development hardware for a Bluetooth project in a windows 7 Guest. We're finding that the new Development boards we've received is not working with 4.3.30 and the nordic tools. The previous hardware that we were using works ok, also the new hardware and tools work fine on the host win7 PC.

It turns out that the UART on the latest development boards requires a DTR signal to be configure the UART Interface MCU pins (which the previous boards did not). Are there any issues with Virtual box virtual com ports which might prevent the DTR signal getting through?

Thanks

MarkH

[mpack]

Is this a real (native) UART, or is it a USB adapter?

[MJH]

It's a micro USB cable. I should also add that we get the same issue with the Nordic USB dongle which also uses a UART connection for communication.

[mpack]

This makes your question hard to answer, since the processing of DTR is entirely dependant on the exact model of USB-serial adapter, and the driver you use.

Are you able to control DTR if the USB device is controlled by the host?

[MJH]

Yes it works fine on the host and we've not encountered any of the issues that have been seen in the VM.

[mpack]

I'm not aware of any problem in VirtualBox, but then I tend not to use VMs to control physical hardware. What is the nature of the DTR use? Does it just need to be held high, or are you pulsing it to put the board into reset?

[MJH]

Hi

No we're just to set it high. We've tried on different VirtualBox VMs and with different cables as well and just got the same result.

Mark.

[mpack]

If it only needs to be held high then it ought to be possible to tie it to 5V at the device end.

Incidentally, I'm too busy (and not highly motivated) to do this, but you could always download the source code and see what signals VirtualBox configures for its virtual serial port. The important part would be its implementation of a virtual MCR (modem control register). It ought to reflect changes in DTR in a host API call. I don't see how it can't, otherwise people would have noticed before. And if, as you say, the host also supports DTR in the API for this port, then I don't see how it can't be working.

You say that you tried different cables... that is slightly disturbing. It should be a work of a moment with a multimeter to prove whether a given cable connects DB9.pin4 end to end. There should be no need for speculation about the cable properties.