Uart Sensor - SensorsUnleashed/Contiki-Device-Link GitHub Wiki

This document is still in development.

This is a contiki APP module, that will make the board ask through the uart which resources is availble.

All actions are forwarded through the uart, and like wise, all readings delivered the other way around.

Operation

Whenever a device has a new value the uart server gets updated. The radio will pass these data on if the update is flagged as an event, else it will be available if a subscriber asks for its current value through the "get" command.

If a subscriber chose to observe a sensor, the sensor will emit new values, based on the setup of the 3 kinds of events:

  • AboveEventAt

    • When a resource crosses this line from low to high give an event (>=)

  • BelowEventAt

    • When resource crosses this line from high to low give an event (<=)

  • ChangeEvent

    • When value has changed more than changeEvent + lastevent value <>= value

  • It is possible to get the event setup by quering the sensor with the get query "eventsetup". eg. counter/timer?eventsetup

  • It is possible to disable all events, by setting the flag "eventsActive" to false. It can be queried by: counter/timer?eventstatus

Protocol description

Messages are SLIP encoded, and all messages ends with the END charater (0xC0)

SEQ NO CMD PAYLOAD LENGTH CRC16
1 byte 1 byte x bytes 1 byte 2 bytes
  • SEQ NO: Will be counting up for each message
  • CMD: Indicates what is to be done. Will be further described later on.
  • LENGTH: Tells the length of the entire message untill the end of the payload. Max is for now 255 bytes.
  • PAYLOAD: The data that should be passed back or forth. The payload is serialized with msgpack
  • CRC16: Contains the checksum for all bytes from SEQ NO to end of PAYLOAD.

Commands (Send from radio to attached device):

0x01 Request number of resource

Returns:

  • Length: 1
  • payload: A number for all the resource available

0x02 Request resource

For each resource served by the client, the resource can be queried by sending the requested index in the payload.

Returns payload:

Message could look like: 0x01, 0x02, "/button/push\0", 0x02, 0x0D, CRC16