'\" t
.\"     Title: modbus_new_rtu
.\"    Author: [see the "AUTHORS" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 10/15/2022
.\"    Manual: libmodbus Manual
.\"    Source: libmodbus v3.1.6
.\"  Language: English
.\"
.TH "MODBUS_NEW_RTU" "3" "10/15/2022" "libmodbus v3\&.1\&.6" "libmodbus Manual"
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.SH "NAME"
modbus_new_rtu \- create a libmodbus context for RTU
.SH "SYNOPSIS"
.sp
\fBmodbus_t *modbus_new_rtu(const char *\fR\fB\fIdevice\fR\fR\fB, int \fR\fB\fIbaud\fR\fR\fB, char \fR\fB\fIparity\fR\fR\fB, int \fR\fB\fIdata_bit\fR\fR\fB, int \fR\fB\fIstop_bit\fR\fR\fB);\fR
.SH "DESCRIPTION"
.sp
The \fBmodbus_new_rtu()\fR function shall allocate and initialize a \fImodbus_t\fR structure to communicate in RTU mode on a serial line\&.
.sp
The \fIdevice\fR argument specifies the name of the serial port handled by the OS, eg\&. "/dev/ttyS0" or "/dev/ttyUSB0"\&. On Windows, it\(cqs necessary to prepend COM name with "\e\e\&.\e" for COM number greater than 9, eg\&. "\e\e\e\e\&.\e\eCOM10"\&. See http://msdn\&.microsoft\&.com/en\-us/library/aa365247(v=vs\&.85)\&.aspx for details
.sp
The \fIbaud\fR argument specifies the baud rate of the communication, eg\&. 9600, 19200, 57600, 115200, etc\&.
.PP
The \fIparity\fR argument can have one of the following values
.RS 4
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fIN\fR
for none
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
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.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
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.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fIO\fR
for odd
.RE
.RE
.sp
The \fIdata_bits\fR argument specifies the number of bits of data, the allowed values are 5, 6, 7 and 8\&.
.sp
The \fIstop_bits\fR argument specifies the bits of stop, the allowed values are 1 and 2\&.
.sp
Once the \fImodbus_t\fR structure is initialized, you must set the slave of your device with \fBmodbus_set_slave\fR(3) and connect to the serial bus with \fBmodbus_connect\fR(3)\&.
.SH "RETURN VALUE"
.sp
The function shall return a pointer to a \fImodbus_t\fR structure if successful\&. Otherwise it shall return NULL and set errno to one of the values defined below\&.
.SH "ERRORS"
.PP
\fBEINVAL\fR
.RS 4
An invalid argument was given\&.
.RE
.PP
\fBENOMEM\fR
.RS 4
Out of memory\&. Possibly, the application hits its memory limit and/or whole system is running out of memory\&.
.RE
.SH "EXAMPLE"
.sp
.if n \{\
.RS 4
.\}
.nf
modbus_t *ctx;

ctx = modbus_new_rtu("/dev/ttyUSB0", 115200, \*(AqN\*(Aq, 8, 1);
if (ctx == NULL) {
    fprintf(stderr, "Unable to create the libmodbus context\en");
    return \-1;
}

modbus_set_slave(ctx, YOUR_DEVICE_ID);

if (modbus_connect(ctx) == \-1) {
    fprintf(stderr, "Connection failed: %s\en", modbus_strerror(errno));
    modbus_free(ctx);
    return \-1;
}
.fi
.if n \{\
.RE
.\}
.SH "SEE ALSO"
.sp
\fBmodbus_new_tcp\fR(3) \fBmodbus_free\fR(3)
.SH "AUTHORS"
.sp
The libmodbus documentation was written by Stéphane Raimbault <stephane\&.raimbault@gmail\&.com>