Digital Input Express VI
- Updated2023-02-21
- 4 minute(s) read
Requires: myRIO Toolkit or roboRIO Toolkit
Reads values from one or more digital input channels on the myRIO or the roboRIO.
This Express VI reads one sample each time with the default FPGA personality on the myRIO. This Express VI reads one sample or multiple samples each time with the high-throughput FPGA personality on the myRIO. Visit ni.com/info and enter the Info Code ex6g5a to learn about the myRIO high-throughput FPGA personality.
This Express VI reads one sample each time with the default FPGA personality on the roboRIO. The roboRIO uses a 5 V voltage rail on the DIO port for powering sensors and provides 3.3 V DIO lines for generating digital input signals.
| Dialog Box Options |
| Block Diagram Inputs |
| Block Diagram Outputs |
Dialog Box Options
| Parameter | Description |
|---|---|
| I/O mode | (myRIO Toolkit) Specifies to read one sample or multiple samples. The default is Digital input (1 sample). This option is available only when you use the myRIO high-throughput FPGA personality. |
| Node name | Specifies the name of this Express VI. You can also double-click the name of this Express VI on the expandable node to edit the name. |
| Channel | Specifies the digital input channel from which to read the value. If the channel you select is set as a digital output channel, this Express VI changes the channel to a digital input channel before reading the value. |
| Custom channel name | Specifies a custom name for the digital input channel that you select. |
| Delete Channel | Deletes the digital input channel that you select. (myRIO Toolkit) If you use the myRIO high-throughput FPGA personality, this option is available only when you specify Digital input (1 sample) for I/O mode. |
| Add Channel | Adds a new digital input channel to the channel list. You can add up to 12 digital input channels. (myRIO Toolkit) If you use the myRIO high-throughput FPGA personality, this option is available only when you specify Digital input (1 sample) for I/O mode. |
| Sample rate | (myRIO Toolkit) Specifies the sampling frequency of the input signal. Valid values are between 1 kHz and 8 MHz. If you specify a frequency that is invalid, this Express VI coerces the specified value to the nearest valid value when you click the Validate button. This option is available only when you use the myRIO high-throughput FPGA personality and specify Digital input (n samples) for I/O mode.
|
| Samples | (myRIO Toolkit) Specifies the number of samples to read. The default is 1,000. Valid values must be greater than 0 and less than or equal to 10,000. This option is available only when you use the myRIO high-throughput FPGA personality and specify Digital output (n samples) for I/O mode. |
| Latency | (myRIO Toolkit) Displays the latency between two adjacent signal acquisition iterations. Refer to the Details section of this topic for more information about latency. This option is available only when you use the myRIO high-throughput FPGA personality and specify Digital input (n samples) for I/O mode. |
| View Code | Displays the underlying code of this Express VI. |
| Connection Diagram | Shows the I/O connector pinouts on the myRIO or the roboRIO. The highlighted pinouts represent the channels that you configure. |
Block Diagram Inputs
| Parameter | Description |
|---|---|
| error in (no error) | Describes error conditions that occur before this node runs. |
Block Diagram Outputs
| Parameter | Description |
|---|---|
| channel name | Returns the value that this Express VI reads from the digital input channel that you select, where channel name is the name of the digital input channel. |
| error out | Contains error information. This output provides standard error out functionality. |
Digital Input Details
(myRIO Toolkit) The following figure demonstrates the latency when you use the Digital Input Express VI with the myRIO high-throughput FPGA personality to perform n samples read operations.
In the previous figure, the x-axis represents time and the y-axis represents amplitude. The waveform in blue represents the signal that the myRIO acquires. The red dotted line represents latency. When latency occurs, the myRIO does not acquire any signal. In other words, the time interval between two adjacent signal acquisition iterations is latency.
Related Information
1 Sample versus N Samples Modes (myRIO Toolkit)
Generating FPGA Clocks (myRIO Toolkit)
Generating FPGA Clocks (roboRIO Toolkit)
I/O Connectors (myRIO Toolkit)
I/O Connectors (roboRIO Toolkit)
Latency in N Samples Read and Write Operations (myRIO Toolkit)