User's Manual

Serial communication protocol

3.3 Serial communication protocol

This protocol is based on a master sending commands and a node answering; the

whole communication is conducted in plain ASCII, as strings. When exchanging

numbers, they are represented in decimal format. All commands are terminated

with a CR/LF combination. All responses (answers) are terminated with the #

character.

3.3.1 General format of a command

The commands have the following format:

ID Command Param1 Param2 ... ParamN

• ID is the destination device. If you include an ID as part of a command, the

node checks whether ID=ownID. If it does, the node executes the

command on itself. If the ID is not the node’s ID, the node executes the

command on a remote device, if such an ID exists. If the ID is missing, this

implies that the command is addressed locally.

Note: Not all the commands can be relayed remotely.

• Command is the command proper, which can be composed of a variable

string of characters (for example,

SLOT). Each node can implement a set of

commands depending on the functionality of the node itself. However, as a

minimum requirement, a node recognizes the CMDS command, which

returns a list with the commands recognized by the node.

• Param1 Param2 ... ParamN represent the parameters, which are

command dependent. If you type no parameters when you issue a

command, it is the equivalent of querying for information (the GET version

of a command). If you type parameters, you are issuing the SET version of

a command and are setting the command to the parameters you typed.

3.3.2 General format of an answer

The answers have the following format:

ID Command Result1 Result2 ... ResultN ErrResult #

• ID is the answering device. If a command was further routed, it is the ID of

the end device. The answer must always contain the ID on return.

• Command is the string representing the original command. It is supplied so

that a master can distinguish between the answers it is waiting for, and out-

of-band notifications (which may come, for example, over the radio port of

a node). As with the ID, the command name must be always supplied.

• Result1 Result2 ... ResultN are the result values returned by the

remote node. If the ErrResult is not zero, all other possible characters

and/or strings until the end of the line may be ignored.

• ErrResult shows whether the command was successfully executed. If

this value is 0, the command was successfully executed. If this value is

other than 0, the command failed. The number may further indicate the

error type. (See also “Returned errors list” on page 43.)