Appendix: Serial programming interface
Introduction
This section of the document describes the remote control protocol for controlling the DT91 via the
RS232 interface.
Conventions
nThe remote controller is referred to as the ‘RC’.
nAll values in this section are hexadecimal values, unless otherwise specified.
Data transfer format
nTransfer rate: 19,200bps.
n1 start bit, 8 data bits, 1 stop bit, no parity, no flow control.
Command and response formats
Communication between the RC and the DT91 takes the form of sequences of bytes, with all commands and responses having the same basic format. Communication between the two is full duplex. The DT91 shall always respond to a received command.
Each transmission by the RC shall be at least five bytes long in the following format: <STR> <CC> <DL> <Data> <ETR>
nSTR (Start transmission): 0x21
nCC (Command code): the code for the command
nDL (Data length): the number of data items following this item, excluding the ETR
nData: the parameters for the command
nETR (End transmission): 0xD
Each response by the DT91 shall be at least six bytes long in the following format: <STR> <RC> <AC> <DL> <Data> <ETR>
nSTR (Start transmission): 0x21
nRC (Reply code): = command code
nAC (Answer code): answer code (see below)
nDL (Data length): the number of data items following this item, excluding the ETR
nData: the information associated with this response
nETR (End transmission): 0xD
Note that the DT91 shall transmit messages whenever its status changes.
State changes as a result of other inputs
It is possible that the state of the DT91 may be changed as a result of user input via the front panel buttons or via the IR remote control. Changes resulting from these inputs shall be relayed to the RC (using the appropriate message type) as they occur.
For example, if the user changed the front panel display brightness using the DISP button on the remote control, a display message (defined below) would be sent to the RC. A similar action would be taken for all other state changes.
Answer codes
The following answer codes are defined: |
| ||
n | Command OK | 0x1: | The command has been accepted and processed completely. |
n | Command Failed | 0x0: | The command has failed for some reason. |
English
DT91
