We have recently developed a product that uses the TUSB3410 to pass serial data between a PC and a H.A.R.T modem device. We are using Windiows 7 32 bit and drive 'TUSB3410 Single Driver Installer v3.3' as downloaded in file swrg094g.zip
At first glance everything seems to be working as expected, using a simple terminal program (C.R.T) and looping back the TX to RX we get what we type.
Writing a simple test program that sends a valid HART protocol frame through the TUSB3410 to our attached test device does cause the device to reply and the response is correctly received back at the PC.
HOWEVER, when we then use third party PC software to talk to our device we find that the reply from our device is never seem by the PC software. The transmit data is being correctly transmitted out of the TUSB on the TX serial pin, and the reply is correctly passed back into the RX pin of the TUSB, however the PC software always reports no RX data seen. We have found the same result on all the third part HART software we have tried to date.
To see if the RX data was actually being passed back to the PC via the USB link we ran a serial port diagnostics package on the PC which told us that the RX data had been received at the PC and that the data was good.
We think the problem may be down to the driver implementation for the virtual serial port. Proper implementation of the HART protocol requires checking of various timing figures relating to the received data (such as time to first character, inter character gap etc.). The third party packages we have tested against were written to use real RS232 ports and may well be checking timing details when validating the returned data. My question is : does the driver that we are using emulate in full the functionality found with a standard RS232 port driver and if not , what are its limitations.
Hoping you can help
Paul Trick
