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RIO Developer Essentials Guide for Academia

Glossary

ad hoc wireless network

A private wireless network in which one host establishes a wireless access point to which other wireless devices can connect.

channel wire

Visual representation of asynchronous data flow between parallel loops (new feature in LabVIEW 2016); intended to simplify designs that rely on traditional inter-process communication techniques such as local and global variables, queues, and notifiers. See also http://www.ni.com/white-paper/53423/en.

deterministic process loop

A special type of while-loop structure that executes with a precisely-defined time per loop iteration. Implemented by the “Timed Loop” structure on the RT target and the “Single Cycle Timed Loop” (SCTL) on the FPGA target. The RIO processor runs the NI Linux Real-Time operating system (RTOS) to combine the advantages of a high-level programming environment with precision timing.

DHCP

Dynamic Host Configuration Protocol, an automatic mechanism to assign IP addresses to hosts on the network. See https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_ProtocolG.

DNS

Domain Name System translates an easy-to-remember IP address such as www.ni.com into its numerical address; analogous to a telephone directory in which you look up the name of a person or business to find their phone number. See https://en.wikipedia.org/wiki/Domain_Name_System.

dot-decimal

Expresses a four-byte binary IP address as four decimal integers (one for each byte) separated by periods, e.g., 172.22.11.2, the IP address of Academic RIO connected by the USBLAN. In dot-hexadecimal form this IP address is FF.FF.FF.F8 which is 11111111.11111111.11111111.11111000 in dot-binary form.

Ethernet hub

Joins more than two Ethernet ports into a single network. Connecting two Ethernet ports together by a single cable establishes a private network that is limited to two hosts, while a hub allows more hosts to join the network.

firewall

Security mechanism that screens undesired traffic into or out of your network. Ports are normally closed by default. A port must be opened to allow your myRIO to be reachable by other computers on the Internet. CAUTION: You must be cognizant of the security risks you take when creating open ports in your firewall!

gateway

The “gateway” host forwards data packets with an out-of-network prefix to a “router” that directs the data packet to its intended network and host. The gateway examines the IP address which contains a network prefix and a host ID; under normal circumstances, data packets may only be delivered to hosts within the same network, i.e., they have the same network prefix. When a host on a given network generates a data packet with a destination IP address whose network prefix does not match the given network, the gateway provides a path out of the given network.

HMI

Human Machine Interface, often a VI running on the PC host that communicates with the RIO RT target via its network connection.

HTTP

HyperText Transport Protocol, the basis of the “world wide web”. See https://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol.

IoT

Internet of Things, i.e., networking in the context of machine-to-machine interactions; ubiquitous communication ability of embedded systems.

IP

Internet Protocol describes the fundamental mechanisms for transferring information in the form of data packets. See https://en.wikipedia.org/wiki/IPv4.

IP address

A numerical representation that uniquely identifies a network and a host within that network. IPv4 (Internet Protocol version 4) address is 32 bits, often expressed in “dot-decimal” notation. For example, the 32-bit address expressed in hexadecimal form as AC160B0A would be written as 172.22.11.10 in dot-decimal notation. IPv6 address is 128 bits.

ISP

Internet Service Provider

jitter

Unpredictable variation in process loop execution time from one iteration to the next. Nondeterministic process loops implemented by the conventional while-loop structure can experience significant timing variation due to subVIs that occasionally require more time to complete a task (e.g., file system and network I/O), shared resource contention, and operating system scheduling for parallel processes and routine housekeeping tasks.

JSON

JavaScript Object Notation (pronounced “JAY-suhn”) structures numeric values, text, and arrays as ASCII text strings; a standard way to communicate information to and from Web services. See JSON Basics: What You Need to Know and The JavaScript Object Notation (JSON) Data Interchange Format.

LAN

Local Area Network

latest value

Transfer only the current (most recent) data value between two process loops or between two targets. Also known as “tag” communication. Latest-value communication involves a single-element lossy buffer that can be accessed by multiple writers and readers.

message

Transfer every value of intermittent data with low latency.

NCSI

Microsoft Network Connectivity Status Indicator, a web service located at http://www.msftncsi.com/ncsi.txt that returns the string “Microsoft NCSI”. The ability to successfully retrieve this string proves the ability of the host to properly connect to the Internet. See https://technet.microsoft.com/en-us/library/cc766017.

network

Collection of hosts (machines that run applications) and the various physical links that allow the hosts to share information.

nondeterministic process loop

A conventional while-loop structure whose execution time may vary unexpectedly from one loop iteration to the next. Sources of nondeterminism include subVIs that sometimes need to wait for a longer period of time, e.g., file system and network I/O, shared resource contention, and task scheduling by the operating system.

port

Specific entry/exit point for a host. 16-bit value corresponds to more than 65,000 available ports, although some port numbers refer to standard networking services, e.g., port 80 associates to the HTTP service. See https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers.

private IP address

Network address of a host connected in a private network that is not connected as part of a public network, i.e., the Internet. Examples of private networks include APIPA (Automatic Private IP Addresses) = 169.254.0.0/16: network formed by hosts in the absence of a DHCP server, e.g., when connecting two myRIO/X-HUB combos together by an Ethernet cable; NI USBLAN = 172.16.0.0/12: network established between myRIO and the PC through the USB cable; consumer home wireless router = 192.168.0.0/16; link local = 127.0.0.0/8: the loopback address, i.e., “talk to yourself”. A gateway/router is required to communicate with hosts outside of the private network. See also https://en.wikipedia.org/wiki/IPv4 and https://en.wikipedia.org/wiki/Private_network.

public IP address

The network address of your host as it appears to other machines on the Internet. Websites such as http://ipinfo.io and http://ipaddress.com display the public IP address of your device. Multiple devices connected by your home’s wireless router all have the same public IP address, because it is actually the router that is known to the Internet by this unique address. The router connects together the various private networks that you have established. Include a port number to make your myRIO uniquely addressable from the Internet.

queue

A memory construct that stores a sequence of messages or data elements, similar to people waiting in line; also known as a FIFO (first-in, first-out) buffer. Normally elements are inserted (“enqueued”) at the back of the queue and retrieved (“dequeued”) at the front of the queue, although at times it is useful to enqueue a high-priority message directly at the front.

router

Links networks together so that data packets originating on a given networks can be delivered to a host on another network.

SMTP

Simple Mail Transport Protocol, a standard for Internet-based email systems.

SSID

Service Set Identifier, the name of a wireless network as it appears to other devices.

streaming

Transfer every data value through a first-in first-out (FIFO) queue. Streaming communication involves a single writer and reader.

subnet mask

A bit mask composed of a block of ones followed by a block of zeros to designate the bits of an IP address that correspond to the network number (ones block) and the host ID (zeros block). For example, the NI USBLAN is a small private network established by the USB cable connecting the laptop/desktop to the Academic RIO. The IP address of the laptop is 172.22.11.1 and the address of the RIO is 172.22.11.2. The subnet mask for this network is 255.255.255.248. Converting the dot-decimal form of the subnet mask to dot-hexadecimal form yields FF.FF.FF.F8 which is 11111111.11111111.11111111.11111000 in dot-binary. Forming the logical “AND” with this bit mask and the laptop IP address yields the network prefix as 172.22.11.0. The remaining three zero bits yield the laptop’s host ID as 1 and the RIO’s host ID as 2. The network prefix may be expressed as 172.22.11.0/29 with the “slash 29” indicating that the network prefix requires 29 bits. This network can theoretically accommodate six hosts; why six? The three-bit field of zeros yields eight possible combinations: 0002 designates the network, 0012 designates the first host, 1102 designates the sixth host, and 1112 designates direct broadcast to all hosts, i.e., every host on the network will accept this data packet as addressed to it. See also https://en.wikipedia.org/wiki/Subnetwork.

tag

Transfer only the current (most recent) data value between two process loops or between two targets. Also known as “latest value” communication. Tag communication involves a single-element lossy buffer that can be accessed by multiple writers and readers.

TCP

Transmission Control Protocol, a connection-based means to send and receive data packets with guaranteed reliability; once the connection is established, data may be exchanged between two peers with acknowledgement of successful transmission; data packets are received in the same order as transmitted; requires more networking resources to maintain the connection. See https://en.wikipedia.org/wiki/Transmission_Control_Protocol.

UDP

User Datagram Protocol, a connectionless protocol based on sending data packets known as datagrams, a word play on “data” and “telegrams.” Requires minimal networking resources. Reliability is not guaranteed, i.e., datagrams can be dropped and arrive out of order Works especially well in local private networks. See https://en.wikipedia.org/wiki/User_Datagram_Protocolh.

USBLAN

USB-based local area network (LAN) established between the Academic RIO and the PC host computer.

WebDAV

Web Distributed Authoring and Versioning, an Internet standard mechanism for editing and managing files between remote systems. With the myRIO “WebDav Client” software set add-on installed and a network connection you can mount the myRIO file system, including externally connected USB drives, as a drive on your Windows, Mac OS, or Linux system and directly manipulate the myRIO-based files as you would any other files on your system.

wireless router

Combines the wireless link and data packet routing function into a single product; requires a connection to an Internet Service Provider, e.g., by a cable modem.

WPA

Wi-Fi Protected Access, a Wi-Fi security standard that encrypts the data transferred between wireless devices.

WPA passphrase

A string containing 8 to 63 printable ASCII characters (can include spaces and symbols) to authenticate clients on a consumer-grade wireless network.

WPA2

Wi-Fi Protected Access 2, also called WPA or WPA2 Personal, a Wi-Fi security standard intended for consumer-grade wireless networks. Uses a “Pre-Shared Key” (PSK), also known as a “WPA Passphrase” to generate the encryption keys.

X-HUB

Combination USB and Ethernet hub designed by Stratom for myRIO. Fits inline with the myRIO power and USB cables, extends the number of available USB ports to three, and adds an Ethernet port for a wired network. See the product page http://sine.ni.com/nips/cds/view/p/lang/en/nid/213322.