Don’t throw away that old computer! If it has a parallel port, you can use it to control your electronic gadgets. Until a few years ago, all computers came equipped with a parallel port, which was used mostly to connect to a printer. Today, most printers connect to computers via USB ports.
How does a beginner learn LabVIEW? Get to the root cause of Java performance issues. Datadog APM provides distributed tracing and real-time analytics for Java apps. Free 14-day trial. Learn More at datadoghq.com. You dismissed this ad. Are there any good tutorials or new user guides out there? Is LabVIEW worth learning? This VI is written in LabVIEW 4.0.1 and will write a string of words out of the serial port and then read them back in. Before running the VI, make sure to set the port channel correctly. In LabVIEW, zero represents the first serial port. Q: Why is my MODBUS device timing out and not receiving responses from LabVIEW? A: First, make sure that your serial port settings match the serial settings for the MODBUS device. Then check your device manual for the type of serial cable you need to communicate with the device. I have this VISA Serial VI which I have used for some time doing RS-232/485 communication. It works OK, but I am no Serial comm expert, so Im not certain what flaws it may contain. LabVIEW 8 attachment. VISA Serial.llb. Share this post. Link to post Share on other sites. LabVIEW VISA Serial VI.
- MODBUS MESSAGING IMPLEMENTATION GUIDE 1.0 8-May-02 www.modbus.org Modbus Messaging Implementation Guide v1.doc page 11/49 Ethernet TCP-IP network and a MODBUS serial line. This field is set by the MODBUS Client in the request and must be returned with the same value in the response by the server.
- Serial-in, serial-out shift registers delay data by one clock time for each stage. They will store a bit of data for each register. A serial-in, serial-out shift register may be one to 64 bits in length, longer if registers or packages are cascaded. The following data was extracted from the CD4006b.
The parallel port has one advantage over USB ports: It makes it easy to create your own circuits that interface directly with the port. These circuits can control low-current devices such as LEDs, or they can activate transistors or even mechanical relays that in turn can activate high-current devices such as motors, incandescent lamps, or sound systems.
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After you’ve created the circuits to connect to a parallel port, it’s a simple matter to create a software program on the computer that sends data to the parallel port. When you run this program, your circuit can detect the data sent to the parallel port to control such things as LEDs or other low-power circuits.
The makeup of a parallel port
A standard parallel port has eight data pins, which are essentially TTL logic outputs, with +5 V HIGH representing 1 and 0 V LOW representing 0. In fact, the first parallel printer ports designed for the IBM PC back in 1980 actually used 7400-series logic chips.
Because of the TTL logic levels used by the parallel port, it’s a simple matter to create logic circuits that interface with the output from a parallel port. And after you build a circuit that connects to a parallel port, it’s a relatively simple matter to use software on the computer to send data to the parallel port. Then your circuit can respond to the data you send.
Unfortunately, few computers today come with a built-in parallel port. Before you waste your time building circuits to interface with a parallel port, you need to find a computer that has one. Your best bet is to scavenge for an old laptop computer. Almost any laptop computer 10 years old or so will do the job, because most computers that age have a parallel port.
If you can’t find a computer with a parallel port, you can buy an inexpensive parallel-port card that adds a parallel port to any computer. Online retailers such as Newegg sell them for less than $15 apiece.
In fact, it’s a good idea to use an add-on parallel port card even if your computer has a built-in parallel port. That’s because if you incorrectly wire the circuit that interfaces with the parallel port, you risk damaging the computer’s internal circuitry. Better to fry a $15 add-on card than your computer’s motherboard.
The DB25 connector and its pins
A parallel printer port uses a standard type of connector called a DB25 connector, which has 25 pins, each of which serves a different purpose in the port’s communication with a printer.
Like most data connectors, DB25 connectors come in both male and female variants. The male DB25 connectors consist of 25 pins, and the female connectors have 25 holes.
The connector consists of two rows of pins. The top row has 13 pins, and the bottom row has 12. The pin in the top-right corner of the female connector is designated as pin 1; the pin at top left is pin 13; pin 14 is at bottom left; and pin 25 is at bottom right.
The pin numbers for a male connector are the mirror images of the numbers of the pins in the female connector. This arrangement is necessary so that when the male connector is plugged into the female connector the pins connect properly (e.g., pin 1 connects to pin 1, pin 2 connects to pin 2, and so on.)
t — Dates and times
array of datetime or duration values
Dates and times, specified as an array of datetime or duration values. The datenum function does not account for time zone information in t and does not adjust datetime values that occur during Daylight Saving Time. That is, datenum treats the TimeZone property of datetime arrays as empty and converts the remaining date and time information to a serial date number.
Data Types: datetime | duration
Date vectors, specified as an m-by-6 or m-by-3 matrix containing m full or partial date vectors, respectively. A full date vector has six elements, specifying year, month, day, hour, minute, and second, in that order. A partial date vector has three elements, specifying year, month, and day, in that order. Each element of DateVector must be a positive or negative integer value except for the seconds element, which can be fractional. If an element falls outside the conventional range, datenum adjusts both that date vector element and the previous element. For example, if the minutes element is 70, then datenum adjusts the hours element by 1 and sets the minutes element to 10. If the minutes element is -15, then datevec decreases the hours element by 1 and sets the minutes element to 45. Month values are an exception. The datenum function sets month values less than 1 to 1.
Example: [2003,10,24,12,45,07]
Data Types: double
DateString — Text representing dates and times
character array | cell vector of character vectors | string vector
Text representing dates and times, specified as a character array where each row contains text representing one point in time, as a cell vector of character vectors, or as a string vector. All rows of a character array, or all elements of a cell vector or string vector, must have the same format.
Example: '24-Oct-2003 12:45:07'
Example: ['19-Sep-2013';'20-Sep-2013';'21-Sep-2013']
Example: {'15-Oct-2010' '20-Nov-2012'}
If the format used in the text is known, you should also specify formatIn. If you do not specify formatIn, then DateString must be in one of the following formats.
Format of Text RepresentingDates and Times | Example |
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Note
The symbolic identifiers describing date and time formats aredifferent from those that describe the display formats of datetime arrays.
Certain formats might not contain enough information to convert text representations of dates and times. In those cases, hours, minutes, and seconds default to 0, days default to 1, months default to January, and years default to the current year. datevec and datenum consider two-character years (e.g., '79') to fall within the 100-year range centered around the current year.
When you do not specify formatIn, note thefollowing:
For the formats that specify the month as two digits(
mm), the month value must not be greater than12.However, for the format
'mm/dd/yy',if the first entry in the text is greater than 12 and the second entryis less than or equal to 12, thendatenumconsidersthe text to be in'yy/mm/dd'format.
formatIn — Format of input text representing dates and times
character vector | string scalar
Format of the input text representing dates and times, specified as a character vector or string scalar of symbolic identifiers.
Example: 'dddd, mmm dd, yyyy'
The following table shows symbolic identifiers that you canuse to construct the formatIn character vector.You can include characters such as a hyphen, space, or colon to separatethe fields.
Note
The symbolic identifiers describing date and time formats aredifferent from the identifiers that describe the display formats of datetime arrays.
Symbolic Identifier | Description | Example |
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| Year in full |
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| Month using capitalized first letter |
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The formatIn value must follow these guidelines:
You cannot specify any field more than once. For example,you cannot use
'yy-mmm-dd-m'because it has twomonth identifiers. The one exception to this is that you can combineone instance ofddwith one instance of any ofthe other day identifiers. For example,'dddd mmm dd yyyy'isa valid input.When you use
AMorPM,theHHfield is also required.You only can use
QQalone or witha year specifier.
PivotYear — Start year of 100-year date range
present minus 50 years (default) | integer
Start year of the 100-year date range in which a two-characteryear resides, specified as an integer. Use a pivot year to interpretdates that specify the year as two characters.
If formatIn contains the time of day, thepivot year is computed from the current time of the current day, month,and year. Otherwise it is computed from midnight of the current day,month, and year.
Example: 2000
Note
If the input date format specifies a four-character year, thenthe last two characters are truncated, and the first twocharacters specify the year. For example, if the date and pivot yearare specified as ('25122015','ddmmyyyy',2000),then the resulting date is 25-12-2020, not 25-12-2015.
Data Types: double
Year, month, and day arrays specified as numeric arrays. These arrays must be the same size, or any one can be a scalar. The values in Y,M,D must be integer values.
If Y,M,D are all scalars or all column vectors,you can specify the input arguments as a date vector, [Y,M,D].
Example: 2003,10,24
Data Types: double
Y,M,D,H,MN,S — Year, month, day, hour, minute, and second arrays
numeric arrays
Year, month, day, hour, minute, and second arrays specified as numeric arrays. These arrays must be the same size, or any one can be a scalar. datenum does not accept milliseconds as a separate input, but as a fractional part of the seconds input, S. The values in Y,M,D,H,MN must be integer values.
If Y,M,D,H,MN,S are all scalars or all column vectors, you can specify the input arguments as a date vector, [Y,M,D,H,MN,S].
Example: 2003,10,24,12,45,07.451
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Data Types: double