PJON Dynamic Addressing Spec v0.1

/*
Milan, Italy - 02/10/2016
The PJON™ dynamic addressing specification is an invention and intellectual property
of Giovanni Blu Mitolo - Copyright 2010-2017 All rights reserved

Related work: https://github.com/gioblu/PJON/
Compliant implementation versions: PJON 5.2 and following

Inspired by the thesis of Thomas Snaidero:
"Modular components for eye tracking, in the interest of helping persons with severely impaired motor skills."
Master Thesis, IT University of Copenhagen, Denmark, September 2016
*/

###PJON™ dynamic addressing specification v0.1 This draft defines the dynamic addressing procedure used by a device in multi-master configuration or the one imposed and regulated by the master in a master-slave configuration.

###Master-slave dynamic addressing

  SLAVES
   _________     _________     _________     _________
  | ID    1 |   | ID    2 |   | ID    3 |   | ID    4 |     
  | RID 101 |   | RID  41 |   | RID 945 |   | RID  22 |      __________
  |_________|   |_________|   |_________|   |_________|     |  MASTER  |
______|_____________|_____________|_____________|___________| ID   254 |
      ___|_____     ___|_____     ___|_____     ___|_____   |__________|
     | ID    5 |   | ID    6 |   | ID    7 |   | ID    8 |             
     | RID 723 |   | RID  35 |   | RID 585 |   | RID  66 |               
     |_________|   |_________|   |_________|   |_________|

####Master features

  • The master id is PJON_MASTER_ID (value 254)
  • Master has a caducous internal device archive
  • Broadcasts PJON_ID_LIST to get PJON_ID_REFRESH requests from already approved devices
  • Handles PJON_ID_REQUEST requests from devices asking for device id assignment
  • Sends PJON_ID_NEGATE request to colliding or inconsistent devices
  • Handles PJON_ID_NEGATE requests from slaves who are leaving the bus

####Slave features

  • The slave initial device id is PJON_NOT_ASSIGNED (value 255)
  • Slaves have a unique random generated 4 bytes id or rid
  • Sends PJON_ID_REFRESH request to master if required by master PJON_ID_LIST broadcast
  • Sends PJON_ID_REQUEST to master if device id assignment is necessary
  • Regenerates rid and restarts the process if PJON_ID_NEGATE is received from master
  • Sends PJON_ID_NEGATE before shut down / leaving the bus
  • Fall back to multi-master procedure if no master is present

####Procedure Slave sends an PJON_ID_REQUEST to get a new device id:

  ___________ __________ ________ ____________ _______ _______ _______ _______ _____     _____
 |           |  HEADER  |        |            |       |       |       |       |     |   |     |
>| MASTER_ID | 00010100 | LENGTH | ID_REQUEST | RID 1 | RID 2 | RID 3 | RID 4 | CRC |> <| ACK |
 |___________|__________|________|____________|_______|_______|_______|_______|_____|   |_____|

If master detects a device rid collision, sends a PJON_ID_NEGATE request to PJON_NOT_ASSIGNED device id to force the collided device still not approved to regenerate a device rid:

  ______________ __________ ________ ___________ _______ _______ _______ _______ _____     _____
 |              |  HEADER  |        |           |       |       |       |       |     |   |     |
>| NOT_ASSIGNED | 00010100 | LENGTH | ID_NEGATE | RID 1 | RID 2 | RID 3 | RID 4 | CRC |> <| ACK |
 |______________|__________|________|___________|_______|_______|_______|_______|_____|   |_____|

Master broadcasts response containing the new id reserved for the device rid who requested:

  ___________ __________ ________ ____________ _______ _______ _______ _______ ____ _____
 |           |  HEADER  |        |            |       |       |       |       |    |     |
>| BROADCAST | 00010000 | LENGTH | ID_REQUEST | RID 1 | RID 2 | RID 3 | RID 4 | ID | CRC |>
 |___________|__________|________|____________|_______|_______|_______|_______|____|_____|

Slave device id acquisition confirmation:

  ___________ __________ ________ ____________ _______ _______ _______ _______ ____ _____     _____
 |           |  HEADER  |        |            |       |       |       |       |    |     |   |     |
>| MASTER_ID | 00010100 | LENGTH | ID_CONFIRM | RID 1 | RID 2 | RID 3 | RID 4 | ID | CRC |> <| ACK |
 |___________|__________|________|____________|_______|_______|_______|_______|____|_____|   |_____|

If master detects reference inconsistencies at this stage, sends a PJON_ID_NEGATE request to the slave id to force the device requesting ID_CONFIRM to regenerate a rid and try again:

  ____ __________ ________ ___________ _______ _______ _______ _______ _____     _____
 |    |  HEADER  |        |           |       |       |       |       |     |   |     |
>| ID | 00010100 | LENGTH | ID_NEGATE | RID 1 | RID 2 | RID 3 | RID 4 | CRC |> <| ACK |
 |____|__________|________|___________|_______|_______|_______|_______|_____|   |_____|

If master experience temporary disconnection / malfunction on startup sends a PJON_ID_LIST broadcast request. Slaves will receive the broadcast and dispatch an PJON_ID_REFRESH request for the master:

Master broadcast PJON_ID_LIST request:

  ___________ __________ ________ _________ _____
 |           |  HEADER  |        |         |     |
>| BROADCAST | 00010000 | LENGTH | ID_LIST | CRC |>
 |___________|__________|________|_________|_____|

Slave device PJON_ID_REFRESH request:

  ___________ __________ ________ ____________ _______ _______ _______ _______ ____ _____     _____
 |           |  HEADER  |        |            |       |       |       |       |    |     |   |     |
>| MASTER_ID | 00010100 | LENGTH | ID_REFRESH | RID 1 | RID 2 | RID 3 | RID 4 | ID | CRC |> <| ACK |
 |___________|__________|________|____________|_______|_______|_______|_______|____|_____|   |_____|

If the id requested by the slave is free in the reference, id is approved by the master and the exchange ends. If the id is found already in use, the master sends an PJON_ID_NEGATE request forcing the slave to acquire a new id through an PJON_ID_REQUEST:

Master sends PJON_ID_NEGATE request to the slave:

  _______ __________ ________ ___________ _______ _______ _______ _______ _____     _____
 | SLAVE |  HEADER  |        |           |       |       |       |       |     |   |     |
>|  ID   | 00010100 | LENGTH | ID_NEGATE | RID 1 | RID 2 | RID 3 | RID 4 | CRC |> <| ACK |
 |_______|__________|________|___________|_______|_______|_______|_______|_____|   |_____|

If slave wants to leave the bus must send a PJON_ID_NEGATE request to the master:

  ___________ __________ ________ ___________ _______ _______ _______ _______ ____ _____     _____
 |           |  HEADER  |        |           |       |       |       |       |    |     |   |     |
>| MASTER_ID | 00010100 | LENGTH | ID_NEGATE | RID 1 | RID 2 | RID 3 | RID 4 | ID | CRC |> <| ACK |
 |___________|__________|________|___________|_______|_______|_______|_______|____|_____|   |_____|

###Multi-master dynamic addressing

    _______     _______     _______     _______     _______
   |       |   |       |   |       |   |       |   |       |  
   | ID 0  |   | ID 1  |   | ID 2  |   | ID 3  |   | ID 4  |  
   |_______|   |_______|   |_______|   |_______|   |_______|    
 ______|___________|___________|___________|___________|______
          ___|___     ___|___     ___|___     ___|___
         |       |   |       |   |       |   |       |   
         | ID 5  |   | ID 6  |   | ID 7  |   | ID 8  |
         |_______|   |_______|   |_______|   |_______|

####Procedure In a multi-master scenario, the device actively looks for a free device id and make no use of its rid for this procedure:

  1. The device extracts a random device id and tries to contact that device
  2. If an answer is received, it adds one to the id and tries again
  3. If any answer is obtained from a device id, that is reserved
  4. The device receives for a random time to be able to answer to other devices interested in that device id
  5. The device tries to contact itself to probe collision, if no answer is received the device id is taken.