Time-out limit of the 8451-I2C interface for hold-master condition

[UnexpectedLifeForm]

I am working with Windows XP, Labview 8 and the USB-8451 I2C to USB interface-box.

We intend to incorporate the USB-8451 into our product evaluation kits for a new sensor product.

This evaluation kits should be used by our customers when they start working with our sensor products.

The I2C-device is a digital sensor which generates a hold-master condition with difference length, depending on the sensor configuration.

The hold-master is produced by the sensor after full transmassion of  start-bit, address, read-bit and ACK.

After the hold master is suspended three bytes can be read by the master.

If the hold-master is kept by the sensor for 25 ms or less I have no problems. When keeping it significantly longer the interface seems not to work properly anymore. I don't get a LabView Error-Message but the PC (Windows?) creates a 'ding-dong' sound very similar to disconnecting and connection a USB device. (the 8451???). My LabView-Program does not show sensor data after this.

I can imagine that the hold-master is somehow too long for one element in the system.

Is there any time-out period for hold-master defined for the USB-8451?

How can I change it to higher values?

Thank you very much for your support!

Message Edited by UnexpectedLifeForm on 02-19-2007 09:48 AM

[Nick_CH]

Dear Member,

I'm wondering why you did not reveive any help about your question. it doesn't matter...
Did you still have the issue with your usb-8451?

Best regards
Nick_CH

[UnexpectedLifeForm]

As we were going to buy a certain quantity of this devices we got great support from NI.
With a new firmware-version this watchdog-problem will be eliminated.
First tests have been successful.
Many thanks.

[Nick_CH]

Dear Member,

That's right. If somebody encounter this problem again.
You should contact your local NI branch that will install the new firmware version (that works with the last driver version)

Best regards,
Nick_CH