Write Binary Data to the ISU

Command Format:

+SBDWB=[<SBD message length>]

This command is used to transfer a binary SBD message from the FA to the single mobile originated buffer in the ISU. The mobile originated buffer can contain only one message at any one time.

  • Once the command is entered, the ISU will indicate to the FA that it is prepared to receive the message by sending the ASCII encoded string READY<CR><LF> (hex 52 45 41 44 59 0D 0A) to the FA.

  • The <SBD message length> parameter represents the length, in bytes, of the SBD message not including the mandatory two-byte checksum.

  • The maximum mobile originated SBD message length is 340 bytes. The minimum mobile originated SBD message length is 1 byte.

  • Once the FA receives the READY indication from the ISU, the SBD message must be sent from the FA formatted as follows:

{binary SBD message} + {2-byte checksum}

  • The checksum is the least significant 2-bytes of the summation of the entire SBD message. The high order byte must be sent first. For example if the FA were to send the word “hello” encoded in ASCII to the ISU the binary stream would be hex 68 65 6c 6c 6f 02 14.

  • The mobile originated buffer will be empty upon power-up.

  • If any data is currently in the mobile originated buffer, it will be overwritten.

Command Response:

0

SBD message successfully written to the ISU.

1

SBD message write timeout. An insufficient number of bytes were transferred to ISU during
the transfer period of 60 seconds.

2

SBD message checksum sent from DTE does not match the checksum calculated at the ISU.

3

SBD message size is not correct. The maximum mobile originated SBD message length is 340 bytes. The minimum mobile originated SBD message length is 1 byte.

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Bug?

Note: AT+SBDWB returns one of the 4 responses above (0, 1, 2, 3) with 0 indicating success. In all cases except response 1, the response is followed by result code ‘OK’. This could be considered a bug, but has been present since the very first SBD release so has not been fixed for fear of breaking existing applications.