libmodbus/doc/modbus_read_bits.txt

modbus_read_bits(3)
===================


NAME
----
modbus_read_bits - read many bits


SYNOPSIS
--------
*int modbus_read_bits(modbus_t *'ctx', int 'addr', int 'nb', uint8_t *'dest');*


DESCRIPTION
-----------
The _modbus_read_bits()_ function shall read the status of the 'nb' bits (coils)
to the address 'addr' of the remote device. The result of reading is stored in
'dest' array as unsigned bytes (8 bits) set to _TRUE_ or _FALSE_.

You must take care to allocate enough memory to store the results in 'dest'
(at least 'nb' * sizeof(uint8_t)).

The function uses the Modbus function code 0x01 (read coil status).


RETURN VALUE
------------
The _modbus_read_bits()_ function shall return the number of read bits if
successful. Otherwise it shall return -1 and set errno.


ERRORS
------
EMBMDATA::
Too many bits requested


SEE ALSO
--------
linkmb:modbus_write_bit[3]
linkmb:modbus_write_bits[3]


AUTHORS
-------
The libmodbus documentation was written by Stéphane Raimbault
<stephane.raimbault@gmail.com>