MCC DAQ Sync Quantity

[Ricky Ooi]

Hi,

I have 2 USB1808 and 2 QUAD08 as shown in the diagram attached. In order to make all DAQs sync to each other, I had connected the wire between ICLKO (master) and ICLKI (slave) / XPCR (slave). 

When I run my program, I observed all DAQs were triggered started because I displayed out the "curIndex" obtained from "GetStatus" function in C# and there is a reading. On second time I get the "curIndex", I noticed the the reading from one of the slave device (QUAD08 B1) does not change anymore. So, I am suspecting the slave device had been lost of sync connection. After few minute of run, the "curIndex" of another slave device (QUAD08 B0) does not change anymore. 

At first, I was thinking this is due to my program issue. So, I purposely update my code to non-sync mode (that mean all slave DAQ are not running at ExtClock trigger), and surprisingly the DAQ worked very well. Therefore, I am confidence that this might be due to lost of sync signal by the slave device which causing by insufficient voltage/current from clock signal output by Master device.

Therefore, below are my questions:
1. How many Slave DAQ can be supported by a Master USB1808
2. Any specific condition for the sync cable to connect more than 2 slave devices.
3. Any alternate solutions for this if i would like to have 4 DAQ devices to sync each other if Master device cannot support too many slave devices.

Edited September 5 by Ricky Ooi

[Fausto]

Hello @Ricky Ooi.

We do not have data regarding the number of slave devices able to be clocked by a master USB-1808.  Below are the USB-1808 clock output specifications.

 

If you have been successful with syncing a USB-QUAD08 with the USB-1808 in the past, then verify all the wire connections.  What are the lengths of all the clock wires?  Run your test again and when you notice the count index stop increasing on the USB-QUAD08, then disconnect the clock wire from the USB-QUAD08 and connect it to an oscilloscope.  What does the signal level look like from the USB-1808, while your application is still running?

Regards,

Fausto

[Ricky Ooi]

Hi @Fausto,

I did measure the clock signal voltage value before. However, I never got so high voltage before as shown by the image from you. What I got was around 0.07V, but it still managed to trigger the slave for data collection. Perhaps you can check again from your side and see if my observation is correct or not.

[Fausto]

@Ricky Ooi,

The clock signal from my USB-1808X was approximately 4.72 V.  When I connected the clock signal to an USB-QUAD08, then level dropped to approximately 4.48 V.  I do not have another USB-QUAD08 to test the signal level, but when I connected an USB-CTR08, the clock level did not change.  Please measure your master clock signal level for each additional daq device added.  If the clock level drops significantly as you stated, then swap it with your other USB-1808 device.  Also, please verify that all wires are secured by the screw terminals.

Lastly, are you using a desktop PC or laptop?  If laptop, is it externally powered or running via battery only?

Regards,

Fausto

[Ricky Ooi]

@Fausto,

Do I need to call  "BoardConfig.SetInputPacerOut()" to enable ICLKO for USB1808?

 

[Fausto]

You do not need to call that function for the USB-1808.

[Ricky Ooi]

@Fausto,

I used USB1808 to measure the ICLKO signal voltage. Below is the connection I made. Then, I used DAQami to view the signal result, unfortunately, the signal voltage does not behave as you said (as shown in the image below).

[Fausto]

@Ricky Ooi,

Since the analog input's sampling rate is the same frequency as the output clock (ICKLO), you only get one data point per clock on the input channel.  Instead, connect an oscilloscope to the ICKLO and GND terminals to view the clock signal.