sRead (Function)

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Help / WLanguage / WLanguage functions / Standard functions / Windows functions / Serial/Parallel Ports functions

Miscellaneous
Transmission between two stations using different string formats (Unicode and ANSI)
Using an external library: RXTX
Features specific to Android and Android widget

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sRead (Function)

In french: sLit

Reads a character string in the entry buffer of the specified serial port. The port must be opened beforehand (sOpen).

Remarks:

This function cannot be used with a parallel port.
This function affects the server.
Infrared ports are not supported.
Only serial ports are supported.

Example

// Lecture dans la variable Message de 20 caractères dans
// le buffer d'entrée de COM1
Mess is string
Mess = sRead(1, 20)

Syntax

Reading a number of bytes and retrieving a string Hide the details

<Result> = sRead(<Port number> , <Number of bytes to read>)

<Result>: Character string

Character string read in the entry buffer,
0 if the read operation was not performed.

<Port number>: Integer

Serial port number: 1, 2, 3, ... 32 for COM1, COM2, COM3, ... COM32.
Identifier of the serial port returned by sOpen (if this function was called with a serial port name).
Only this type of parameter is available.

<Number of bytes to read>: Integer

Number of bytes to read in the entry buffer of the serial port. The number of bytes to read is returned by sInEntryQueue.

Remarks

Miscellaneous

sOpen has no effect if the port was not opened by sRead.
sRead clears the input queue of bytes actually read.
A 32-bit application is locked during the duration of the transfer. To avoid this lock, the timeout between two read operations must be specified in sOpen. If the timeout is reached and the data could not be read, sRead returns 0.
WLanguage does not support control signals.
The time to wait for a character to be read or written is specified with sOpen.
- If this time is set to 1s when reading 1024 bytes, the waiting time will be 1024s.
- If this time is set to "-1s" when reading 1024 bytes, the waiting time will be 1s.
This prevents lock problems when reading from or writing to the print port.

Transmission between two stations using different string formats (Unicode and ANSI)

When transmitting messages between two stations using a different string format (e.g. Windows (ANSI) and Windows Mobile (Unicode)), certain conversions are necessary:


Format of character strings on the current computer	Write operation (sWrite function)	Read operation (sRead function)
Format of character strings on the current computer	Write operation (sWrite function)	Buffer containing an ANSI string	Buffer containing a string in Unicode format
ANSI (PC running Windows for example)	The character string will be in ANSI format	No conversion is required	Conversion required (UnicodeToAnsi)
Unicode	The character string will be in Unicode format	Conversion required (AnsiToUnicode)	No conversion is required

Special case for Linux:

Only serial ports can be opened and initialized.
By default, users do not have access to serial ports. It is necessary to grant them specific rights to manage serial ports.

Using an external library: RXTX

In Java, the use of serial and parallel port manipulation functions (functions sOpen, sWrite, sRead, ...) requires the presence of an external library: RXTX.

This library includes a Jar archive and one or more native libraries that depend on the operating system on which the application is run. To use these functions:

the Jar archive (RXTXComm.jar) must:
- be found in the same directory as the Java application generated by WINDEV,
- be found in the execution classpath of the application,
- be directly included in the generated application (from the wizard for Java generation).
the native libraries corresponding to the operating system on which the application is run must be found:
- in the same directory as the Java application generated by WINDEV,
- in the path of the application libraries (librarypath).

You can download the RXTX library and its documentation from the following link: http://users.frii.com/jarvi/rxtx/index.html (link valid at the time of writing).

Attention: Infrared port management not available in Java.

Features specific to Android and Android widget

In Android and Android widget mode, the serial and parallel port functions can be used:

Only on serial (not parallel or infrared) ports.
Only with devices that support the CDC/ACM protocol (Arduino ATmega32U4) and the following USB to serial converter chips:
- FTDI FT232R, FT232H, FT2232H, FT4232H, FT230X, FT231X, FT234XD
- Silabs CP210x
- Qinheng CH340, CH341A
- Prolific PL2303

Business / UI classification: Business Logic

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