NI DAQ channel terminal in MATLAB is read-only

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Hyalex Ortho
Hyalex Ortho 2023-2-27
回答： Hyalex Ortho 2023-3-1
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.

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Hyalex Ortho
Hyalex Ortho 2023-3-1
I realized I need to change the 'ctr0'/'ctr1'/'ctr2' when adding the input. Device pinout on the NI MAX was helpful.

更多回答（1 个）

chrisw23
chrisw23 2023-2-28
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.
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Hyalex Ortho
Hyalex Ortho 2023-3-1
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
chrisw23 2023-3-1
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

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