Transmit ASCII data

Here's how to transmit ASCII data from your RockBLOCK


Line endings

Note that RockBLOCK expects commands to be terminated with a carriage return (\r) character.

Using a line-feed (\n) character will not work!

With your RockBLOCK connected to a suitable power supply, check that your serial communications are established (default 19200, 8N1) and issue the following commands.

/* Issue AT command */


/* Receive response */


/* Turn off Flow Control */


/* Receive response */


/* Insert ASCII message into MO buffer */

AT+SBDWT=Hello World\r 

/* Receive response */


/* Initiate an Extended SBD Session */


/* Receive response */ 

+SBDIX: <MO status>, <MOMSN>, <MT status>, <MTMSN>, <MT length>, <MT queued>\r

/* See SBDIX Key for information on each parameter */



The SBDIX command denotes the status of your sent, received and queued messages:

- Any returned number with a value of 0 to 2 indicates your message has been successfully transmitted. Any number above 2 indicates that the message has not been successfully transmitted.

- This number denotes the MO message number and cycles between 0 and 65535.

0 - No messages waiting to be received. 1 - New message successfully received. 2 - Error during mailbox check / message reception.

- This number denotes the MT message number and cycles between 0 and 65535.

- The size (in bytes) of the MT message.

- The number of MT messages in the queue waiting to be downloaded.

An SBDIX response of 0,0,0,0,0,0 indicates that a message was transmitted successfully, that there were no MT messages downloaded during this SBD session and that no messages are waiting in the queue to be downloaded.


Further information on AT commands

Please refer to the Iridium ISU AT Command Reference for more information on the available AT commands.

AT commands in this chapter