6052E LIN

[mike_lan]

Hi DirkW.

Thanks for the vi. I see what you mean by comparing the HW timestamps as opposed to the software ones. It makes sense.
The vi does seem now to measure down to uS range now which is more accurate, but occasionally the measurement gives back measurements over 10ms for some reason. Also occasionally it gives negative numbers indicating the LED came on before the message arrived to turn on the LED. I increased the voltage comparison to over 1.4v but no difference. My maximum voltage is 1.5v at the analog input pin.

I reduced my clk/trig/gnd cable from the 6052 to the LIN 8476 device hoping that would correct the timing but no difference. It is approx 15cm now.

Do you know when the LIN device generates the Timestamp ?, Is it after before or during the LIN frame is sent.
This would at least tell me when I have a correct measurement.

[DirkW]

Hi,

I modified the Vi a little bit to take care of the time increment for DAQ. I didn't  thought about it in the first version. Thus we allways had t0 for the conpare. DAQ aquires with 1 KHz and that means your timestamp resolution is 1 us. Keep that in mind.

DirkW

[mike_lan]

Hi DirkW,

Thanks for all your help. Sorry for not replying sooner to your previous post.
Unfortunately the timing is still inaccurate and sometimes it tends to report negative times still.
Perhaps the LIN 8476 device is not accurate enough for this type of measurement with its timestamp?
Your previous mail mentioned accuracy to 1us with 1kHz DAQ, maybe you meant 1ms ?

As a solution I have used a scope to measure the time and I have connected it via GPIB and am now measuring it that way.
The disadvantage to this of course is that it is not flexible if an array of LEDs were to be measured as the scope lead would have to be moved each time, but it may have to do.

Thanks again.