JSON Query by Example

FireStep/Arduino accepts serial command lines. Each command line must be a syntactically complete JSON string with no embedded line breaks. FireStep JSON commands are query by example, and each JSON response will match the structure of the corresponding JSON request.

Example: Show system information

A FireStep request consists of a single line of JSON. Attributes with empty string values are query placeholders:

{"sys":""}

A FireStep response is also a single line of JSON:

{"s":0,"r":{"sys":{"b":"7cc07fa08132","fr":1000,"li":false,"tc":12345,"v":1.0}},'t':0.05}

The top-level attributes of a FireStep response are:

Attribute	✏️	Value

s	| --	| command [status code](https://github.com/firepick1/FireStep/blob/master/src/Status.h)
r	| --	| response matching request structure
t	| --	| total command processing time in seconds

The attributes of each response are patterned after the request. For more information, see the JSON Reference

Attribute	✏️	Value

fr	| --	| least available free ram in bytes (may decrease after certain commands)
li	| :pencil2:	| invert limit (false:HIGH, true:LOW)
tc	| --	| thread clock ticks (@64microseconds)
v	| --	| version

Example: Show system version and free ram

We can be selective about the information we want:

{"sys":{"v":"","fr":""}}

In general, FireStep will scan your request and construct an identical response, only updating query placeholders (i.g., ""). Our response will look like:

{"s":0,"r":{"sys":{"v":1.0,"fr":1000},"t":0.05}}

Example: Show system version

For even greater brevity, FireStep accepts compound attributes. We can combine a primary attribute (e.g., "sys") with a secondary attribute (e.g., "v") to request a single value using a compound attribute (e.g., "sysv"):

{"sysv":""}

The FireStep response will match the request, and use the compound sysv attribute:

{"s":0,"r":{"sysv":1.0},"t":0.05}

Example: Set limit switch mode

You can update one or more values in a request, and even include query placeholders:

{"sysli":true, "sysv":""}

The response will have the same structure as the request:

{"s":0,"r":{"sysli":true, "sysv":1.0}}

Most FireStep values are updateable. Some, such as the system version, cannot be changed.

See Also

• JSON-Query-by-Example
• JSON-Reference
• Delta-V-Stroke