USB Serial Virtual COM port : Read not working

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Hello Everyone,

I am not writing everything again here, because lot more depth is discussed at link below.

Please help.
Thx,
-Varun

http://social.msdn.microsoft.com/Forums/en-US/b65e4ff9-a7ce-4818-8e36-9db75fe8f49f/usb-serial-virtual-com-port-read-not-working?forum=vcgeneral[^]

Posted 10-Mar-14 0:15am

varun mishra

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Rage 10-Mar-14 9:08am

Is your handle valid ?
Some stabs in the dark
Have you open the stream with GENERIC_ALL ?
Have you tried reading without writing before (configure your hw to poll out values) ?

2 solutions

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bling · Answer 1 · 2014-03-10T06:11:00

Solution 1

Try turning on the DTR pin. The device may ignore input when that pin is inactive.

Posted 10-Mar-14 6:11am

bling

Updated 10-Mar-14 6:12am

v2

varun mishra · Answer 2 · 2014-04-07T05:20:00

Hi Guys,

Issue is solved. I had to add wait till InQueue > 0 (it means there is atleast 1 byte in receive buffer) or timeout (as safety exit) is over. it would be blocking call but it is OK for my application at the moment. waitComm() did not work well for me here.

sample snippet:

while(1)
    {
        ClearCommError((HANDLE)*h_drv, (LPDWORD)&Err, &CST);

        if((CST.cbInQue >0)||(count >1000000))
        break;

        count++;
    }