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Contemporary Research 25 IP-HDVR HD Tuner-DVR
Ethernet and
RS-232 Control Protocol
Overview
The IP-HDVR full duplex Ethernet/RS-232 scheme enables a system programmer to control all TV Tuner
functions as well as monitor 3 groups of TV Tuner status. All commands are sent as ASCII strings. No delays
between characters or commands are required, as data is interrupt driven and buffered.
The 3 status groups are: Channel/Source Select, Audio Levels/Mode and Front Panel. The Mute A/V button-
function status from the IP-HDVR front panel has been grouped with the Channel/Source for simplicity in the
most common modes of operation. Each of the groups has one ASCII status response string containing all of
the status data for that group. The current status string of a group is sent from the IP-HDVR whenever a
valid command for that group is received by the IP-HDVR RS-232 port or front panel. A group's status may
be requested at any time via the RS-232 port. Status of all 3 groups is sent at power up. The format of each
group's status response string remains the same always.
Up to 9 IP-HDVR units may be cabled together and addressed for individual control from a single RS-232
port. Each IP-HDVR is assigned a unique unit code.
Communications parameters (Front Panel Mode 1) are 300 to 9600 baud, 8 data bits, No parity, and 1 stop
bit. Factory default is 9600 baud, Unit#1.
All settings are saved to NVRAM in the IP-HDVR.
The tuner will accept non-standard RS-232 control such as voltage that swings from 0 to +5 VDC, commonly
found when IR ports are used to send RS-232 commands.
General protocol specifications
Characters in command strings to the IP-HDVR are common ASCII keyboard characters.
Command strings sent to the IP-HDVR begin with the ASCII > (greater than symbol) as an 'Attention'
character and end with carriage return - ASCII CR, Hex $0D, or keyboard Enter - as an 'End-of-command'
character.
Responses from the IP-HDVR begin with the ASCII < (less than symbol) as an 'Attention' character and end
with a carriage return followed by line feed an ASCII LF or Hex $0A as 'End-of-command' characters.
A carriage return is required at the end of each command and is assumed in all examples.
Command String Structure
[Attention] (Unit#) [Command] (Parameters) [Return]
Attention Single character (>) starts the string
Unit# The Unit# is expressed as an ASCII 0-9 when used in multiple tuner applications.
To address all units, use a Unit # of 0 (Zero)
No unit number will default to Unit#1
Command A two-character command
Parameters Added attributes to some commands
Return A carriage return ends the command string, you may use ASCII CR, Hex $0D, or keyboard
‘Enter’ in programming. For simplicity, the programming examples in the manual will not
show the ‘CR’ – so remember, you’ll need to add it in your control code.