'\" t
.\"     Title: modbus_rtu_set_rts
.\"    Author: [see the "AUTHORS" section]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 02/28/2020
.\"    Manual: libmodbus Manual
.\"    Source: libmodbus v3.1.6
.\"  Language: English
.\"
.TH "MODBUS_RTU_SET_RTS" "3" "02/28/2020" "libmodbus v3\&.1\&.6" "libmodbus Manual"
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.SH "NAME"
modbus_rtu_set_rts \- set the RTS mode in RTU
.SH "SYNOPSIS"
.sp
\fBint modbus_rtu_set_rts(modbus_t *\fR\fB\fIctx\fR\fR\fB, int \fR\fB\fImode\fR\fR\fB)\fR
.SH "DESCRIPTION"
.sp
The \fBmodbus_rtu_set_rts()\fR function shall set the Request To Send mode to communicate on a RS485 serial bus\&. By default, the mode is set to MODBUS_RTU_RTS_NONE and no signal is issued before writing data on the wire\&.
.sp
To enable the RTS mode, the values MODBUS_RTU_RTS_UP or MODBUS_RTU_RTS_DOWN must be used, these modes enable the RTS mode and set the polarity at the same time\&. When MODBUS_RTU_RTS_UP is used, an ioctl call is made with RTS flag enabled then data is written on the bus after a delay of 1 ms, then another ioctl call is made with the RTS flag disabled and again a delay of 1 ms occurs\&. The MODBUS_RTU_RTS_DOWN mode applies the same procedure but with an inverted RTS flag\&.
.sp
This function can only be used with a context using a RTU backend\&.
.SH "RETURN VALUE"
.sp
The function shall return 0 if successful\&. Otherwise it shall return \-1 and set errno to one of the values defined below\&.
.SH "ERRORS"
.PP
\fBEINVAL\fR
.RS 4
The libmodbus backend isn\(cqt RTU or the mode given in argument is invalid\&.
.RE
.SH "EXAMPLE"
.PP
\fBEnable the RTS mode with positive polarity\fR. 
.sp
.if n \{\
.RS 4
.\}
.nf
modbus_t *ctx;
uint16_t tab_reg[10];

ctx = modbus_new_rtu("/dev/ttyS0", 115200, \*(AqN\*(Aq, 8, 1);
modbus_set_slave(ctx, 1);
modbus_rtu_set_serial_mode(ctx, MODBUS_RTU_RS485);
modbus_rtu_set_rts(ctx, MODBUS_RTU_RTS_UP);

if (modbus_connect(ctx) == \-1) {
    fprintf(stderr, "Connexion failed: %s\en", modbus_strerror(errno));
    modbus_free(ctx);
    return \-1;
}

rc = modbus_read_registers(ctx, 0, 7, tab_reg);
if (rc == \-1) {
    fprintf(stderr, "%s\en", modbus_strerror(errno));
    return \-1;
}

modbus_close(ctx);
modbus_free(ctx);
.fi
.if n \{\
.RE
.\}
.sp
.SH "SEE ALSO"
.sp
\fBmodbus_rtu_get_rts\fR(3)
.SH "AUTHORS"
.sp
The libmodbus documentation was written by Stéphane Raimbault <stephane\&.raimbault@gmail\&.com>