Arcam DV29 manual Appendix Serial programming interface, Command and response formats

Appendix: Serial programming interface

Introduction

This section of the document describes the remote control protocol for controlling the DV29 via the

RS232 interface.

Conventions

nThe remote controller is referred to as the ‘RC’, with the DV29 called the ‘DV29’.

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 DV29 takes the form of sequences of ASCII characters, with all commands and responses having the same basic format. With the exception of status triggers (see below), the DV29 shall transmit only to respond to communication from the RC. The DV29 shall always respond to a received command.

Each transmission by the RC shall be five bytes long in the following format: <STR> <CC> <P1> <P2> <ETR>

nSTR (Start transmission): 0x21

nCC (Command code): the code for the command

nPx (Parameter code): the parameters for the command

nETR (End transmission): 0xD

Each response by the DV29 shall be seven bytes long in the following format: <STR> <RC> <AC> <P1> <P2> <P3> <ETR>

nSTR (Start transmission): 0x21

nRC (Reply code): = command code

nAC (Answer code): answer code (see below)

nPx (Parameter code): the parameters for the reponse

nETR (End transmission): 0xD

The RC shall transmit commands and receive answers according to the following procedure:

1.The RC shall transmit a command.

2.Having issued a command, the RC shall wait at least 100ms before transmitting a subsequent command (otherwise commands may be lost). Ideally, the RC shall wait for an answer from the DV29 before issuing the next command.

3.The RC shall analyse the RC, AC and Px values of a received message to decide whether the command has been executed normally.

4.The time from the completion of command transmission by the RC to the beginning of the response by the DV29 shall be maximum two seconds.

5.The DV29 shall not accept any commands from the RC for five seconds after the power switch is turned on or a ‘power-on’ command is recieved.

The exception to the above communication protocol is when ‘status triggers’ are enabled by the RC (using the ‘Status Triggers’ command). In this case, the DV29 shall transmit messages whenever the status of the player changes. These messages shall be transmitted by the DV29 at asynchronous intervals.

State changes as a result of other inputs

It is possible that the state of the DV29 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) only if ‘status triggers’ have been enabled by the RC.

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:

nCommand OK ‘@’ (0x40): The command has been accepted and processed completely.

nCommand ACC ‘A’ (0x41): The command has been accepted but not yet processed fully.

nStatus update ‘B’ (0x42): Status change message

nInvalid command ‘0’ (0x30): The command or command format was invalid

nInvalid request ‘5’ (0x35): The command is not valid for the current player state

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