Conditions

Regular events fire only when a channel changes state. A condition, in contrast, is evaluated when a state is entered: if the configured channel (or global timer) is already in the specified state, the corresponding Condition{N} event fires immediately. This allows states to be skipped based on the current state of a channel rather than waiting for a change to occur.

In this example, Condition2 is met while Port2 is high. If that is the case when the state Port2Light is entered, the Condition2 event fires and the state machine advances to Port3Light without waiting for the one-second state timer to expire.

Python

from bpod_core.fsm import StateMachine

fsm = StateMachine()

fsm.set_condition(
    index=2,
    channel='Port2',
    value=True,  # condition is true when Port2 is high
)

fsm.add_state(
    name='Port1Light',
    timer=1,
    transitions={'Tup': 'Port2Light'},
    actions={'PWM1': 255},
)
fsm.add_state(
    name='Port2Light',
    timer=1,
    transitions={'Tup': 'Port3Light', 'Condition2': 'Port3Light'},
    actions={'PWM2': 255},
)
fsm.add_state(
    name='Port3Light',
    timer=1,
    transitions={'Tup': '>exit'},
    actions={'PWM3': 255},
)

JSON

{
  "states": {
    "Port1Light": {
      "timer": 1.0,
      "transitions": {
        "Tup": "Port2Light"
      },
      "actions": {
        "PWM1": 255
      }
    },
    "Port2Light": {
      "timer": 1.0,
      "transitions": {
        "Tup": "Port3Light",
        "Condition2": "Port3Light"
      },
      "actions": {
        "PWM2": 255
      }
    },
    "Port3Light": {
      "timer": 1.0,
      "transitions": {
        "Tup": ">exit"
      },
      "actions": {
        "PWM3": 255
      }
    }
  },
  "conditions": {
    "2": {
      "channel": "Port2",
      "value": true
    }
  }
}

YAML

states:
  Port1Light:
    timer: 1.0
    transitions:
      Tup: Port2Light
    actions:
      PWM1: 255
  Port2Light:
    timer: 1.0
    transitions:
      Tup: Port3Light
      Condition2: Port3Light
    actions:
      PWM2: 255
  Port3Light:
    timer: 1.0
    transitions:
      Tup: '>exit'
    actions:
      PWM3: 255
conditions:
  2:
    channel: Port2
    value: true