Fieldstrength and RSSI

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Incoming, Outgoing Fieldstrength and RSSI: The difference

Particle Computers provide 3 options to set/get fieldstrenght information:

  1. The sending Particle sets the fieldstrength via an API command. Then all following outgoing packets send from this particle are send with this signal strenght.
  2. The receiving Particle can get the sending fieldstrength (this means the fieldstrength the packet was send by the sender) information from the received packet (see packet description for more information about the AwareCon packet in general).
  3. The receiving Particle can measure the Received Signal Strength Information (RSSI) via a analog port.

Differences between the 2/1x and 2/2x Particles

The difference between the two platform is the use of RSSI (item 3 of the above list). 2/1x is only prepared for measurement while 2/2x integrates the RSSI measurement. To retrieve precise RSSI measurement with the 2/1x particle you have to solder the tiny RSSI-Board to the Particle.

Set Sending/Outgoing Fieldstrength

Particle Computers allow to adjust the sending (outgoing) fieldstrength by calling the API void ACLSetFieldStrength(int power); in the awarcon#xx.c file. This sets the field strength of the transmitted signals. Valid parameters for power are 0..32 with 0 beeing the minimum transmit power. Turning the transmission power down reduces the range where possible receivers can receive the transmitted packets.Minimum transmit power corresponds to 0.01mW (<1m data transmission); maximum to 1mW (>100m outdoors, >10m office). The steps are nearly linear. After calling this function all subseqential packets are sent using this fieldstrength. The current fieldstrength for the Particle can be retrieved via the int LLGetFieldStrength(); function
See the AwareCon Function reference for more information about the API.

Retrieving Sending Fieldstrength of received packet

All packets received by a particle contain the fieldstrength with which they where sent by the sender. To retrieve this information you need to include the signalstrenght.c file, The ACLPktRSS() returns the sending Fieldstrength of the last received packet. Valid parameters for power are 0..32 with 0 beeing the minimum transmit power. Turning the transmission power down reduces the range where possible receivers can receive the transmitted packets.Minimum transmit power corresponds to 0.01mW (<1m data transmission); maximum to 1mW (>100m outdoors, >10m office). The steps are nearly linear.

Receiving Signal Strength (RSSI) of the incoming packet

The receiving Singal Strength analogue value can be measured on the processors A1 pin (Analog 1) on the particle (for 2/1x you need the extra RSSI-Board, see above). API and description will be available January 2005.