// Regenerate using graphviz/dotty with this command
//   dot -Tjpg ./flight/Doc/Architecture/ahrs_spi_link_fsm.dot > ./flight/Doc/Architecture/ahrs_spi_link_fsm.jpg

digraph ahrs_spi_protocol {
  label="AHRS SPI Link State Machine"
  labelloc=t
  labeljust = l

  // Stopped -- Undefined Wire State
  {
    node [ style=filled,color=lightgray ]

    stopped [ shape="doublecircle" ]
    stopping
  }

  // Wire State Inactive
  {
    node [ style=filled,color=lightblue ]

    inactive
  }

  // Wire State Busy
  {
    node [ style=filled,color=red ]

    user_busy
    user_busy_tx_pending
    user_busy_rx_pending
    user_busy_rxtx_pending
  }
  {
    node [ style=filled,color=yellow ]

    user_tx_pending
    user_rx_pending
    user_rxtx_pending
  }

  // Wire State Ready
  {
    node [ style=filled,color=green ]

    user_rx_active
    user_tx_active
    user_rxtx_active
  }

  //
  // State transitions driven by the user
  //
  stopped                -> inactive               [ label="init link" ]

  inactive               -> stopping               [ label="stop" ]
  inactive               -> user_busy_rx_pending   [ label="user set rx" ]
  inactive               -> user_busy_tx_pending   [ label="user set tx" ]

  user_busy              -> user_busy_tx_pending   [ label="user set tx" ]
  user_busy              -> user_busy_rx_pending   [ label="user set rx" ]
  user_busy              -> inactive               [ label="user done" ]
  user_busy              -> stopping               [ label="stop" ]

  user_busy_tx_pending   -> user_busy_rxtx_pending [ label="user set rx" ]
  user_busy_tx_pending   -> user_tx_pending        [ label="user done" ]

  user_busy_rx_pending   -> user_busy_rxtx_pending [ label="user set tx" ]
  user_busy_rx_pending   -> user_rx_pending        [ label="user done" ]

  user_busy_rxtx_pending -> user_rxtx_pending      [ label="user done" ]

  // 
  // State transitions driven by messaging from the OP board
  //
  stopping               -> stopped                [ label="rx any" ]

  user_tx_pending        -> user_tx_active         [ label="rx any" ]
  user_rx_pending        -> user_rx_active         [ label="rx any" ]

  user_rxtx_pending      -> user_rxtx_active       [ label="rx any" ]

  // Active -> Busy
  user_rx_active         -> user_busy              [ label="rx user" ]

  user_tx_active         -> inactive               [ label="rx any" ]

  user_rxtx_active       -> user_busy              [ label="rx user" ]
  user_rxtx_active       -> user_rx_active         [ label="rx link" ]
  user_rxtx_active       -> user_rx_active         [ label="rx unknown" ]
}