How to change the timebase of NI-9469?

[pelican]

I'm working on development of data acquisition software using NI-DAQmx and VC++. I need to change the sample timebase clock of the NI-9469 from 13.1072 MHz to 12.8 MHz, but I'm encountering difficulties.

Two cDAQ chassis (NI-cDAQ9189) were linked using NI-9469, which were inserted into slot#14 of both chassis (cDAQ1Mod14 and cDAQ2Mod14). The remaining slots in both chassis were occupied by multiple DAQ units (NI-9202).

When I checked the default sample timebase clock using following code:

char timebase[256];

DAQmxGetSampClkTimebaseSrc(taskHandlename[k],timebase,256) 

The timebase was "/cDAQ1Mod14/13.1072MHzTimebase," indicating a default setting of 13.1072 MHz.

However, when I attempted to change the timabase from 13.1072 MHz to 12.8 MHz using:

DAQmxSetSampClkTimebaseSrc( board_no, "/cDAQ1Mod14/12.8MHzTimebase" )

I immediatly received a fatal error (-200308) with the message: "Specified sample timebase rate does not match specified sample timebase source. Do not set the sample timebase rate when you are using an internal sample timebase source. In this case, the driver sets the sample timebase rate for you." The timebase didn't change.

How can I resolve the fatal error -200308 and successfully change the timebase?

[ZYOng]

I think you need to specify the Sample Clock Timebase Rate. Timebase of NI-9469 is not internal to the NI-9202.

Reference:

Synchronizing C Series Delta-Sigma Modules in Multiple cDAQ Chassis

Synchronize Multiple cDAQ or cRIO Chassis Using the NI-9469 Module

Using NI-9469 to Synchronize Two cDAQ Chassis

[pelican]

Thank you for your comment.

The NI-9469 can provide two options for sampling base clock, 13.1072 MHz and 12.8 MHz. I understand this is a different clock source from the one in the NI-9202. I once attempted to set the timebase to the internal timebase of the NI-9202, which is 12.8 MHz. But when the two chassis were linked by NI-9469, the timebase source was automatically switched to NI-9469 for some reason even if I explicitly set it to the NI-9202. So I would like to the sample timebase clock of NI-9469 to 12.8 MHz.

[ZYOng · Accepted solution]

What I meant was on top of calling DAQmxSetSampClkTimebaseSrc, you might need to call DAQmxSetSampClkTimebaseRate as well, since you are using a timebase external to NI-9202.

[pelican]

Thank you for your comment. I will try that and feedback to you.