Simultaneous data acquisition on NI 9219 and 9234 mounted on 9174 socket - Matlab

[hideyuki_masuda]

Hi everyone.

I am trying to acquire data simultaneously with a "fast" cDAQ Module (NI 9234) where I need a 6400Hz sample rate, and a slow-sample module (NI 9219) which maximum sample rate is 100Hz (measurements on a load cell, "high speed" ADC Timing Mode.

I can acquire data on an analog input of the 9234 module by initializing so :

chan1=s.addAnalogInputChannel(out(1).ID,'ai0','Voltage');
chan1.Coupling = 'DC';
chan1.InputType = 'PseudoDifferential';
s.Rate = 6400;

as well as I can acquire data from my load cell with the 9219 :

chan3=s.addAnalogInputChannel(out(3).ID,'ai0','Bridge');
chan3.BridgeMode = 'Full';
chan3.NominalBridgeResistance = 10000;
chan3.ADCTimingMode = 'HighSpeed';

s.Rate = 100;

However, when I try to acquire it on both signals, there is a conflict on sample rates : On the one hand, the 9234 minimum SR is 1651.6129 Hz, on the other hand the 9219 minimum SR is 100Hz. The following (contradictory) warnings appear :

Warning: A channel that does not support on-demand operations was added to the session. On-demand operations using inputSingleScan and outputSingleScan will be disabled. Only clocked operations using startForeground and startBackground can be done.
Warning: The Rate property was increased to 1651.6129 due to changes in the session configuration.

Warning: A channel that does not support clocked sampling was added to the session. Clocked operations using startForeground and startBackground will be disabled. Only on-demand operations using inputSingleScan and outputSingleScan can be done.  

Warning: This property must be the same for all channels on this device. All channels associated with this device were updated.

After this, the sample rate of my session is 0 and I get an error if I try to change it.

This page and this other one let me think that 1) I can use slow sample modules and faster modules together and 2) the 9174 Socket can do this... However, I explored the session properties and I cannot find a way to get rid of this sample rate conflict between the modules.

Do anybody have any experience about this ? A mean to force both modules to collaborate ?

Thanks in advance for helping.