USB virtual COM port / direct access so slow !

[tgq]

hi
i just create a hi/lo loop on DTR line with FTDI virtual COM port driver for FT232AM chip, and i get from 50 to 110 Hz response depending on Windoze priority
i use VB and Windoze 'regular' access to com port
anybody has experience how to get it faster ?

 

[elektryk]

Did You try to specyfy priority level od thread/process that pools for DTR line (it is just idea, not tested)

 

[jourval]

Very strange, I use FTDI chip for interfacing microcontroller Rs232 to PC USB port and get transfer rate up to 1 Mbit, btw max rate
I get with PC with win2k, the same comp with Win-98 get 256 kb max..

 

[Mr_Programmer]

tgq:
I have the same problems with commercial USB->seriell adapters. If somebody has a solution please pm me.
By the way, the problem is not the transfer speed via RXD and TXD, the problem is the slow speed of the support lines (DTR, CTS, and so on).

Greetings @all

 

[artem]

USB device can not make interrupt (if it is not OTG ccompliant device ) , so may be there is different pooling frequences for data and control signal made from host topwards device . If it is so , nothing except driver can be blamed .

 

[tgq]

elektryk:
yes with high level priority it gives 110Hz :roll:

Mr_Programmer:
yes exactly ! do u have experience with FTDI 'direct' dll ?

artem:
yes, i'm not sure the 'direct' FTDI dll is able to command or read each line (DTR, CTS, and so on).