Home
Quickstart Guide
Introduction RIO Academic RIO Application examples Your first RT app Your first FPGA app
Real-Time
Basic procedures System admin File system I/O monitor System controller architecture Timed loops Inter-process communication RT/Host communication RT/FPGA communication FPGA personalities Interrupts Datalogger (file I/O)
FPGA
Design flow Simulation Inter-process communication RT/host communication Derived clock domain IP blocks FPGA personality
Networking
Get connected Email Web services UDP TCP IP addresses
Site Map
Guides Code examples Procedures Tags LabVIEW block diagram elements Targets Communications All pages
Glossary How to use About
RIO Developer Essentials Guide for Academia

Site map: Code examples

LabVIEW PC block diagram snippet: PC reads and writes FPGA I/O nodes in simulation mode

"Desktop Execution" node as an FPGA VI testbench
FPGA code PC code

The PC VI interacts with the FPGA VI in simulation mode to apply a test sequence as the FPGA VI input and monitor the resulting output sequence.

LabVIEW FPGA block diagram snippet: Timed loop with 10-MHz derived clock domain highlighted

Derived clock domains
FPGA code

Use a derived clock domain to effectively speed up or slow down the FPGA's 40-MHz clock for a selected portion of the FPGA block diagram.

LabVIEW FPGA block diagram snippet: VHDL code for a 4-bit Johnson counter inserted into an IP Integration node

"IP Integration" node for VHDL code reuse
FPGA code

Reuse existing and validated VHDL-based circuit functionality in the FPGA block diagram instead of developing new LabVIEW G code to implement the same functionality.

LabVIEW FPGA block diagram subpalette for Xilinx IP functions

Xilinx IP integration
FPGA code

Configure and use Xilinx IP (intellectual property) modules designed specifically for the Xilinx Zynq FPGA

LabVIEW PC block diagram snippet: Get PC system time and adjust RT system time to match

Set RT system time/date from PC
RT code PC code

Use the "Set Time" function to adjust the RT system time to match the (assumed accurate) PC system time. Restart the RT target to save the current RT time to be reloaded on each reboot of the Academic RIO Device.

LabVIEW RT block diagram snippet: Use TCP to read current time from NIST time server, parse and validate the returned string, update the RT system time accordingly

Synchronize the system clock to a NIST time source
RT code

Synchronize the system clock time based on querying the Internet Time Service (ITS) maintained NIST (National Institute of Standards and Technology): Open a TCP/IP connection to the "Daytime Protocol" port 13, read the 51-character string, parse the string for time and date information, validate the result (look for a server health indicator and a "magic string"), and then adjust the system time.

LabVIEW RT block diagram snippet: Open a datalog file, get onboard accelerometer measurement, log the measurement to a file, and close the file

Headless datalogger and file I/O
RT code

Monitor process variables and sensor measurements, timestamp them, and log them to a file, and then remote access the datalog file through the network with WebDAV, web browser, or VI running on a PC host.

LabVIEW RT block diagram snippet: Timed loop (deterministic process loop) with loop time measurement indicator and LED blinker

Timed loop
RT code

Use the "Timed Loop" to create a deterministic process loop, i.e., a loop that runs with a precisely-defined time per iteration.

LabVIEW RT block diagram: Measure the number of elapsed RT ticks per loop iteration

Measure loop iteration time
RT code

Use the "Tick Count" function to measure the total elapsed time per iteration of a process loop.

LabVIEW RT block diagram snippet: Create a digital input transition IRQ (interrupt request), associate with a callback VI

Externally-triggered action using interrupt request (IRQ)
RT code

Run a callback VI each time that a digital input transition or an analog input voltage threshold crossing generates an interrupt request (IRQ).

LabVIEW RT block diagram snippet: Create a timer IRQ (interrupt request), associate with a callback VI

Timer-driven background process using interrupt request (IRQ)
RT code

Run a callback VI each time that an FPGA-based interval timer generates an interrupt request (IRQ).

LabVIEW RT block diagram snippet: Process Loop #1 writes an indicator, Process Loop #2 reads the indicator value with a local variable

Local variable (RT)
RT code

Use a local variable (front-panel indicator) to communicate between two parallel process loops contained within the same VI, and use a local variable to stop parallel loops with one "stop" button.

LabVIEW RT block diagrams: VI #1 writes a global variable, VI #2 reads the same global variable

Global variable (RT)
RT code

Use a global variable to communicate between two parallel process loops contained within different VIs under the same target, and use a global variable to stop parallel loops with one "stop" button.

LabVIEW RT block diagram snippet: Read a single-process shared variable in one process loop that was written by another process loop

Single-process shared variable (SPSV)
RT code

A single-process shared variable (SPSV) behaves like a global variable that links deterministic and non-deterministic process loops, effectively shielding the deterministic loop from elements that contribute jitter.

LabVIEW RT block diagram snippet: Functional global variable subVI with unitialized while-loop shift register and case structure

Functional global variable (FGV)
RT code

Use a functional global variable (FGV) to communicate between two parallel process loops contained within different VIs under the same target, and use a FGV to stop parallel loops with one "stop" button. The "functional" nature of the FGV means that you can create additional functionality beyond that of a basic global variable, e.g., counting and calculations that operate on the stored value.

LabVIEW RT block diagram: for-loop structure enqueues 10 integers, then another for-loop structure dequeues the same elements

Queue
RT code

Use a queue to send messages and data between two or more parallel process loops contained within a VI or other VIs. Queues also serve as the foundation for the "Queued State Machine" design pattern.

LabVIEW RT block diagram snippet: Process Loop #1 writes a channel wire, Process Loop #2 reads the channel wire

Channel wire
RT code

Use a channel wire to communicate between two (or more) parallel process loops contained within the same VI, and use a channel wire to stop parallel loops with one "stop" button. Requires LabVIEW 2016 or later version.

LabVIEW FPGA block diagram snippet: Process Loop #1 writes an indicator, Process Loop #2 reads the indicator value with a local variable

Local variable (FPGA)
FPGA code

Use a local variable (front-panel indicator) to communicate between two parallel process loops contained within the same VI.

LabVIEW FPGA block diagrams: VI #1 writes a global variable, VI #2 reads the same global variable

Global variable (FPGA)
FPGA code

Use a global variable to communicate between two parallel process loops contained within different VIs under the same target.

LabVIEW FPGA block diagram snippet: RT VI operates the FPGA front panel

Programmatic front-panel communication with RT
FPGA code RT code

The RT VI operates (writes) the front-panel controls of the FPGA VI and reads its indicators.

LabVIEW RT block diagram snippet: RT and PC read and write the same network-published shared variables

Network-published shared variable (NPSV)
RT code PC code

A network-published shared variable (NPSV) behaves like a global variable that links process loops residing in two or more network-connected targets.

LabVIEW RT block diagram snippet: RT opens a handle to a network-published shared variable and reads its value

Programmatically access a network-published shared variable (NPSV)
RT code PC code

Use the NPSV programmatic API (application programmer's interface) VIs as an alternative method to a shared variable node.

LabVIEW RT block diagram snippet: PC writes one element to a network stream channel, RT reads the element from the same channel

Send messages through a network stream channel
RT code PC code

Send command and status messages through a low-latency lossless network-based data communication channel between the RT target and PC host system.

LabVIEW RT block diagram snippet: RT writes blocks of data to a network stream channel, PC reads the blocks from the same channel

Stream high-speed data through a network stream channel
RT code PC code

Efficiently transfer blocks of data between the RT and PC by network streams.

LabVIEW RT block diagram snippet: Read an audio frame from FPGA DMA FIFO, process the frame, and write the processed frame back to the FPGA

Stream high-speed data between FPGA and RT with a DMA FIFO
FPGA code RT code

Efficiently transfer blocks of data between the RT and FPGA by direct memory access (DMA) first-in first-out (FIFO) buffers.

LabVIEW RT block diagram snippet: Programmatically set a custom FPGA bitfile; alert the VI to expect myRIO default personality functionality on the custom FPGA bitfile

Augmented default Academic RIO Device FPGA personality and high-precision waveform measurement application example
FPGA code RT code

Load and run a modified version of the default Academic RIO Device personality (FPGA bitfile) augmented by user-defined functionality, for example, to make a high-precision measurement of pulse width.

LabVIEW FPGA block diagram snippet: PC VI operates the FPGA front panel

Programmatic front-panel communication with PC
FPGA code PC code

The PC VI operates (writes) the front-panel controls of the FPGA VI and reads its indicators.

LabVIEW PC block diagram snippet: Read an audio frame from FPGA DMA FIFO, process the frame, and write the processed frame back to the FPGA

Stream high-speed data between FPGA and PC with a DMA FIFO
FPGA code PC code

Efficiently transfer blocks of data between the PC and FPGA by direct memory access (DMA) first-in first-out (FIFO) buffers.

LabVIEW RT block diagram snippet: While-loop structure containing guard clause, "Command Parser" kernel subVI, and queue

Queued state machine
RT code

State machines perform system control, data processing, and any task that involves executing a sequence of activities in response to inputs from the surrounding physical system, the user interface, and other processes within the system. The queued state machine is a particular implementation style that is flexible and versatile, easy to maintain, and computationally efficient.

LabVIEW RT block diagram snippet: System Manager and Code Validator message-handling loops

Queued message handler with multiple process loops
RT code

The queued message handler contains multiple process loops operating independently and in parallel that communicate with each other by sending messages through queues. Each process is a well-defined task implemented by the "Queued State Machine" design pattern. Breaking up the system into self-contained tasks greatly simplifies the design of complex systems.

LabVIEW front panels of the "Home Security System" application: RT target with virtual user interface and PC host remote interface

System controller application example: Home Security System
RT code PC code

Example of a complete RT system controller based on the Queued Message Handler (QMH) design pattern with multiple parallel task loops implementing behaviors with queued state machines (QSMs), various inter-process communication techniques (queues and local variables), and inter-target communication techniques (network-published shared variables (NPSVs) and network streams). The PC host human-machine interface (HMI) can remotely connect to the system through the network, monitor the status of the security system, and control it remotely.

LabVIEW PC block diagram: producer-loop contains event structure and guard clause; consumer-loop contains guard clause and case structure; both loops share the same queue reference

Event-driven producer-consumer state machine
PC code

Create a responsive user interface based on two loops operating in parallel: the "producer" loop event structure responds immediately to user interactions such as button clicks and mouse movements that send commands through a queue to the "consumer" loop which performs the required tasks. Separating the state machine into two loops allows the user interface to remain responsive should a consumer task require an unusual amount of time or must wait for a shared resource to become available.

LabVIEW RT/PC block diagram snippet: Use String To IP to determine all known IP addresses for this target, and then render to human-readable form as strings

Show available IP addresses
RT code PC code

Display all of the network IP (Internet Protocol) addresses at which the RT target or PC host can be reached.

LabVIEW RT block diagram snippet: RT checks for Internet access and then sends an email composed of recipients, subject line, and message

Send an email or text message
RT code

Use the Simple Mail Transport Protocol (SMTP) to send an email message; send the email to an SMS (Short Message Service) gateway service to forward the email as a text message.

LabVIEW RT block diagram snippet: RT opens a handle to SMTP email session, sets recipients, message, attachments, and headers, then sends the email message

Send a file as an email attachment with high priority (remote webcam photo logger application)
RT code

Use the low-level Simple Mail Transport Protocol (SMTP) VIs create an email, attach a file, and set the email header to flag the message as 'high priority' in the recipient's email application. The illustrative application example captures webcam images at regular intervals and sends them as email attachments.

LabVIEW RT block diagram: Attempt to open an HTTP connection to the Microsoft Network Connectivity Status Indicator (NCSI) web service as indicator of Internet access

Check Internet access (HTTP method)
RT code PC code

Determine whether or not Internet access is available by attempting an HTTP connection to the "Microsoft Network Connectivity Status Indicator" (NCSI) web service.

LabVIEW RT block diagram: Attempt to open a TCP connection to the Microsoft Network Connectivity Status Indicator (NCSI) web service as indicator of Internet access

Check Internet access (TCP method)
RT code PC code

Determine whether or not Internet access is available by attempting a TCP connection to the "Microsoft Network Connectivity Status Indicator" (NCSI) web service.

LabVIEW RT block diagram snippet: Use TCP to read current time from NIST time server, parse and validate the returned string, update the RT system time accordingly

TCP/IP sender and receiver and "TCP ping" application
RT code PC code

Send TCP/IP messages to a destination IP address and port number, listen for incoming TCP/IP messages on a user-defined port, and echo received messages back to the source. Combine the sender and receiver into a single "TCP ping" application to test the communication channel between two network hosts, and illustrate the notifier method to stop parallel loops with one "stop" button.

LabVIEW RT block diagram snippet: Read the onboard accelerometer and pushbutton, convert to JSON string, and write to TCP channel

TCP client-server
RT code PC code

Create a server on the Academic RIO Device that listens for TCP/IP network connection requests from a client running on the PC host, accepts client information including the desired state of the four onboard LEDs, sets the LEDs accordingly, and returns the state of the onboard 3-axis accelerometer and pushbutton.

LabVIEW RT block diagram snippet: "UDP Sender" loop sends system name and time and 1-second intervals to the destination IP address and port

UDP sender and receiver and "UDP ping" application
RT code PC code

Send UDP messages to a destination IP address and port number, listen for incoming UDP messages on a user-defined port, and echo received messages back to the source. Combine the sender and receiver into a single "UDP ping" application to test the communication channel between two network hosts, and illustrate the notifier method to stop parallel loops with one "stop" button.

LabVIEW RT block diagram snippet: Read the onboard accelerometer and pushbutton, convert to JSON string, and write to UDP channel

UDP client-server
RT code PC code

Create a server on the Academic RIO Device that listens for UDP datagram messages from a client running on the PC host, accepts client information including the desired state of the four onboard LEDs, sets the LEDs accordingly, and returns the state of the onboard 3-axis accelerometer and pushbutton.

LabVIEW RT block diagram snippet: Call an API and parse the returned JSON string

Call a Web service
RT code

Form a query string as a URL, retrieve the JSON string served by the Web service, and parse the JSON string to extract useful information.

LabVIEW RT block diagram snippet: Control onboard LEDs from web form data, return system date/time

Host a Web service
RT code

Host a web service on the Academic RIO Device to serve the states of onboard sensors (pushbutton and accelerometer) and system information (date, time, host name, and IP address), and to control the onboard LEDs based on a user-selected LED hex code.