NI DAQ channel terminal in MATLAB is read-only

Hello, I am using an NI-9422 to read in a signal for motor speed. I am reading in through the data acquisition toolbox in MATLAB. I can read the frequency fine for 1 terminal but I am struggling to understand how to read multiple terminals or a specific terminal.

For instance, the current assigned terminal is PFI5 and if I try to assign a variable ch to my channel and then re-assign the ch.terminal as PFI7 it says it's read only. I've also unplugged, and plugged the chassis back in and the default terminal changes which I can only solve by moving my wires.

What am I missing? Thanks for any help.

Answer 1

[Hyalex Ortho]

I realized I need to change the 'ctr0'/'ctr1'/'ctr2' when adding the input. Device pinout on the NI MAX was helpful.

Answer 2

[chrisw23]

As long as the PFI is configured as Input it should be readOnly.

Each PFI line can be individually configured as a static digital input or a static digital output.

Check the current I/O state.

[Hyalex Ortho]

Meaning I have to use 'addinput' more than once to add in all of my terminals?

[chrisw23]

no way, but as long a s you try to write to an input you will receive a 'read only' warning

[Hyalex Ortho]

I see, I am trying to read in more than 1 input, so how do I pull data in from the other PFI terminals? It seems to default me to PFI5 and I don't know when adding my input how to specify which terminal I'm reading in from. I'm not trying to change the name or write to it, just trying to access a different terminal.

[chrisw23]

I'm not using the DataAcqToolbox but the DAQmx API instead but I think it is similar.

When you define the task you have to add all channels you want to use and you can't get access to a channel that is not defined for that task.

i.e.

obj.ContinuousAnalogInTask.AIChannels.CreateVoltageChannel(...

% physicalChannelName

% nameToAssignChannel (alias)

% enum NationalInstruments.DAQmx.AITerminalConfiguration

% minimumValue

% maximumValue

% NationalInstruments.DAQmx.AIVoltageUnits