USB to 15pin D-SUB of PCI 1426

[SandeepC]

Hi,

I need to connect an external device (GPS) which has a USB port to the D-SUB 15 pin port of the PCI 1426 frame grabber. I know that the USB port has a power and ground pins and two data pins. I also know that USB sends out data in differential voltage. But I am not sure whether the frame grabber can detect differential voltage.

My requirement is to send triggering pulses to the GPS device and read the responses given by the GPS device. I am thinking of using the TTL I/O 1-4 pins of the 1426 for this.

Can any one tell me how this interfacing can be done?

Thanks & Regards,

Sandeep

[Rolf Kalbermatter]

QUOTE (SandeepC @ Mar 31 2009, 11:40 AM)

Hi,

I need to connect an external device (GPS) which has a USB port to the D-SUB 15 pin port of the PCI 1426 frame grabber. I know that the USB port has a power and ground pins and two data pins. I also know that USB sends out data in differential voltage. But I am not sure whether the frame grabber can detect differential voltage.

My requirement is to send triggering pulses to the GPS device and read the responses given by the GPS device. I am thinking of using the TTL I/O 1-4 pins of the 1426 for this.

Can any one tell me how this interfacing can be done?

Thanks & Regards,

Are you seriously considering to write an USB protocol stack in LabVIEW using the RS-422 IO lines of the 1426 card?????? I would really reconsider that again. USB is NOT RS-422 although with an RS-485 port (bidirectional) you probably could simulate it electrically. But that still leaves you with the USB protocol stack to be implemented.

The TTL pins definitly wouldn't be electrically compatible to simulate even the electric aspects of USB.

Why are you even considering to connect that device to this framegrabber. Wouldn't be a direct USB port on the computer where this board is plugged in be a lot easier?

Rolf Kalbermatter

[SandeepC]

Thanks for the reply Rolf.

The reason I am not preferring to connect the device to the USB port of the system is the speed/latency constraint. I need very high speed and low latency and I thought that using the D-SUB port would provide this.

One other idea that I have thought about is the use of a USB to Serial port converter. If I connect the USB port of the device to a USB to Serial port converter cable and connect the data pins of the serial output to the TTL pins of the D-SUB. Would this be possible? (In this option also I am alright with the idea of doing away with sending triggering signals to the GPS which can be operated in auto output mode.)

Please let me know your thoughts regarding this.

Regards,

Sandeep

[Rolf Kalbermatter]

QUOTE (SandeepC @ Apr 1 2009, 04:24 AM)

Thanks for the reply Rolf.

The reason I am not preferring to connect the device to the USB port of the system is the speed/latency constraint. I need very high speed and low latency and I thought that using the D-SUB port would provide this.

One other idea that I have thought about is the use of a USB to Serial port converter. If I connect the USB port of the device to a USB to Serial port converter cable and connect the data pins of the serial output to the TTL pins of the D-SUB. Would this be possible? (In this option also I am alright with the idea of doing away with sending triggering signals to the GPS which can be operated in auto output mode.)

Please let me know your thoughts regarding this.

Lot of work and I'm sure you can never reach the short latency in this way that the native USB port would provide, at least if you have no bad hubs or such in between.

Rolf Kalbermatter