quanser.hardware.task.read_digital :: QUARC MATLAB Functions

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quanser.hardware.task.read_digital

Reads the specified number of digital samples from the task's internal buffer.

Syntax

[values, samples_read, err] = task.read_digital(samples)

Description

Reads the specified number of digital samples from the task's internal buffer. This function will block until the requested number of samples has been read or the task is stopped.

Warning Many cards allow the digital I/O lines to be programmed as inputs or outputs. The digital I/O lines are configured as inputs or outputs using the quanser.hardware.hil.set_digital_directions function. All the channels which will be used as digital inputs must be configured as inputs using this function. Failure to configure the digital I/O may result in the task.read_digital function failing to read those inputs.

If no err output is provided then it throws an exception if an error occurs. In generated code it prints the error message. Use hil_get_error_message to get the message associated with an error code.

Parameters

task

Task instance returned by quanser.hardware.hil.task_create_digital_reader or quanser.hardware.hil.task_create_digital_reader_digital_writer.

samples

The number of samples to read. This number must be less than or equal to the internal buffer size assigned to the task in the quanser.hardware.hil.task_create_digital_reader or quanser.hardware.hil.task_create_digital_reader_digital_writer call.

Outputs

values

A matrix of digital values, as int8s. There is one row for each channel and one column for each sample.

samples_read

The number of samples read. This number will be equal to the number of samples specified unless the total number of samples specified in task.start has expired or the task has been stopped.

err

A negative error code or zero on success.

Examples

% Creates a task to read digital channels 0 and 3, with an internal buffer of 1000 samples.
task  = board.task_create_digital_reader(1000, [0 3]);

% Start the task using SYSTEM_CLOCK_1 at 1 kHz. Collect up to 5000 samples.
task.start(-1, 1000, 5000);

% Reads 500 samples of digital channels 0 and 3. Takes 0.5 seconds to complete read.
for i=1:10
    [values, n] = task.read_digital(500);
    ...
end;

task.stop;
task.close;