5. Communication
5.1.
RS485 interface settings
The RS485 interface is a half-duplex connection with the following parameters:
❏
Baud rate : 19200
❏
Data bits : 8
❏
Stop bits : 1
❏
Parity
: Even
On top of that, a Modbus RTU protocol is in place to handle the data transfer. This is a
master-slave type of protocol, ideal for RS485 data communications. This protocol
supports up to 247 devices on the bus.
5.2.
Input registers (read-only)
Table 18 - Input registers (read only)
Name
Functionality
Address
Length
Distance
Retrieves last read distance along with
the new distance flag which specifies
whether this is a new distance
0x00
2
Circular buffer
Retrieves the buffer holding the last 5
detection distances
0x02
5
5.2.1.
New distance flag
This flag is sent together with the distance data every time. Its purpose is to signal whether
the distance data being sent is a new one compared to the last read by the master. This
flag is an unsigned 16 bit integer with a value of 0 or 1.
5.2.2.
Circular distance buffer (applicable for modes 2, 4 and 5)
This buffer acts as a log for the last 5 detected objects, storing the measured distance to
object. This buffer has to be read entirely every time (length 5), otherwise an error will be
returned.
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