'\" t
.\"     Title: modbus_read_bits
.\"    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_READ_BITS" "3" "10/15/2022" "libmodbus v3\&.1\&.6" "libmodbus Manual"
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.SH "NAME"
modbus_read_bits \- read many bits
.SH "SYNOPSIS"
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\fBint modbus_read_bits(modbus_t *\fR\fB\fIctx\fR\fR\fB, int \fR\fB\fIaddr\fR\fR\fB, int \fR\fB\fInb\fR\fR\fB, uint8_t *\fR\fB\fIdest\fR\fR\fB);\fR
.SH "DESCRIPTION"
.sp
The \fBmodbus_read_bits()\fR function shall read the status of the \fInb\fR bits (coils) to the address \fIaddr\fR of the remote device\&. The result of reading is stored in \fIdest\fR array as unsigned bytes (8 bits) set to TRUE or FALSE\&.
.sp
You must take care to allocate enough memory to store the results in \fIdest\fR (at least \fInb\fR * sizeof(uint8_t))\&.
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The function uses the Modbus function code 0x01 (read coil status)\&.
.SH "RETURN VALUE"
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The function shall return the number of read bits if successful\&. Otherwise it shall return \-1 and set errno\&.
.SH "ERRORS"
.PP
\fBEMBMDATA\fR
.RS 4
Too many bits requested
.RE
.SH "SEE ALSO"
.sp
\fBmodbus_write_bit\fR(3) \fBmodbus_write_bits\fR(3)
.SH "AUTHORS"
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The libmodbus documentation was written by Stéphane Raimbault <stephane\&.raimbault@gmail\&.com>