User's Manual

7 The command interface

7.1 Overview

The module acts as a slave and can be fully controlled by an external host. The conﬁguration

as well as the operation of the module can be managed by predeﬁned commands that are

sent as telegrams over the UART interface of the module.

The commands of the command interface can be divided into 3 groups:

• Requests: The host requests the module to trigger any action, e.g. in case of the

request

CMD_RESET_REQ

the host asks the module to perform a reset.

• Conﬁrmations: On each request, the module answers with a conﬁrmation message

to give a feedback on the requested operation status. In case of a

CMD_RESET_REQ

the module answers with a

CMD_RESET_CNF

to tell the host whether the reset will be

performed or not.

• Indications and Responses: The module indicates spontaneously when a special event

has occurred. The

CMD_DATAEX_IND

indicates for example that data was received via

radio.

Start signal Command Length Payload CS

0x02 1 Byte 1 Byte Length Bytes 1 Byte

Start signal 0x02 (1 Byte)

Command One of the predeﬁned commands (1 Byte), the module implements new and

modiﬁed commands in comparison to other radio compatible modules.

Length Speciﬁes the number of payload data in the following ﬁeld.

Payload Variable number (deﬁned by the length ﬁeld) of data or parameters.

Checksum Byte wise XOR combination of all preceding Bytes including the start signal, i.e.

0x02 ˆ Command ˆ Length ˆ Payload = CS

All commands of type Request must obey the following rules:

• Only one request at a time may be active. Wait for conﬁrmation of the previous re-

quest and implement a suiting timeout (depends on the command or action that was

requested, 500ms should cover the worst-case time).

• Indications are spontaneous messages, they may occur in between a command re-

quest and its conﬁrmation.

• A high /RTS line signalizes that the module UART is not ready for reception. Thus,

any byte(s) sent from the host will be discarded by the module without further user

notiﬁcation ("module busy"). If "module busy" occurs while sending a command to

the module, it is necessary to resend this entire command again after /RTS pin status

shows "module idle" again.