Ascii Hex Mode; Scope; Physical Connection; Line Signalling Information - Hydronix Hydro-View HV02 User Manual

ASCII Hex mode

The ASCII-Hex mode uses a communications protocol which is designed to be simple to
implement and test whilst allowing a reasonable degree of performance to be achieved. It
should be possible to implement a suitable driver from most high level languages such as
'C' or BASIC running on standard PC-compatibles or even BASIC modules in
programmable controllers whilst 'trials' can be performed from standard communications
programs such as Microsoft Windows 'Terminal', Hayes 'Smartcom' etc.
Driver code for such applications is beyond the scope of this manual.

Scope

Using ASCII-Hex protocol you can perform tasks via the Hydro-View serial port such as...
Read instantaneous (NOW) moisture value.
Read average moisture value.
Read set-point output status flags.
Read average/hold status.
Read level input status.
Set current material number.
The Hydro-View communications port acts as a SLAVE device when running the ASCII-
Hex protocol i.e. it will transmit data only in response to requests from your external
device.
Future issues of the Hydro-View system firmware will support additional operations via the
serial port and these will be documented in updates to engineering note EN0005 and later
incorporated into this manual.

Physical connection

The ASCII-Hex protocol can be used on either the RS232 port which is fitted as standard
to all Hydro-View units or on the optional RS485 port which may be fitted as an optional
extra.

Line signalling information

The ASCII-Hex protocol operates only at 9600 baud, using 8 data bits, 1 stop bit and no
parity.

Basic frame format

Data frames on the communications link are constructed as indicated in the table below.
Field
STX
STATION
Format Description
02 Start of frame.
Two Represents the station number of the relevant
ASCII-Hex Hydro-View.
characters Valid slave station numbers are in the range 01-7F
(1-127 decimal).
Reply frames from slave stations have the top bit of
the station number set and thus reply station number
fields are in the range 81-FF.
The purpose of this mechanism is to allow
discrimination between request and reply data
frames over a two-wire RS485 link.
USING HYDRO-VIEW SERIAL PORTS
HYDRO-VIEW USER GUIDE D0022 REV 1.06
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