Reference Manual

7. The command interface
The command interface on the Calypso enables full control over the module using ASCII
based AT styled commands. In order to support easy integration with a wide range of micro-
controllers, two different modes of the command interface are implemented. The user can
choose one of the following modes by setting the two APP_MODE_x pins to the correspond-
ing levels as described in section 5.2 .
1. Terminal mode : In this mode the module behaves like a standard serial terminal. All
characters received are looped back to the host and an action is triggered on receiving
a "\r\n" (hex: 0x0D0A). The module supports backspace character "\b" in this mode.
All user data has to be Base64 encoded as binary data transmission is not allowed in
this mode of operation.
2. Normal mode : This is the standard mode without terminal characteristics. The re-
ceived characters are not echoed. However, the host receives an explicit acknowl-
edgement for every command it receives and triggers an action on receiving a "\r\n"
(hex: 0x0D0A). In this mode, the user data can be binary as well as Base64.
7.1. Command types
There are three types of messages exchanged between the calypso and the host.
• Requests: The host requests the module to perform an action or start an operation.
All Requests start with the "AT+" tag and end with "\r\n" (hex: 0x0D0A).
• Confirmations: On each request, the module answers with a confirmation message to
give a feedback on the requested operation status.
All Confirms contain the Request itself and either a "OK" or an error code. Appendix B
gives a brief description of all the error codes. All confirmations end with "\r\n" (hex:
0x0D0A).
• Events: The module indicates spontaneously when a special event has occurred. All
events start with the "+" tag and contain further data, error codes (see Appendix B ) or
status information. All events end with "\r\n" (hex: 0x0D0A).
7.2. AT command characteristics
This section describes the syntax and detailed characteristics of the aforementioned three
command types.
7.2.1. Request
The generic syntax of an AT command request is as shown below :
AT+<command name> = <param1> , <param2> , . . . , <paramX>
• All commands start with the prefix "AT". The delimiter "+" indicates the beginning of
the command name.
Calypso reference manual version 1.2 © April 2019
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