State machine logic

Introduction to the Bpod state machine

The Bpod system's behavior on each experimental trial is programmed as a virtual finite state machine. This ensures precise timing of events - for any state machine you program, state transitions will be completed in less than 100 microseconds - so inefficient coding won't reduce the precision of events in your data.

• Each state sets Bpod's outputs (Valves, LEDs, TTL I/O, etc).
• Events detected by Bpod can be set to trigger transitions between specific states.

Here is a simple finite state machine, describing a binary switch that controls a bulb with variable brightness:

stateDiagram
direction LR
onstate: On state\nBrightness 100
offstate: Off state\nBrightness 0
onstate --> offstate: Switched off
offstate --> onstate: Switched on

• Each state contains a name ("On state" or "Off state"), a hardware description ("Brightness: X"), and events that trigger state transitions ("Switched on/off")

Here is the same diagram presented as a Bpod state machine description:

sma = NewStateMachine();   % Initializes a new, empty state machine
                           % description struct called "sma".

% Now add a new state called "OnState" to the description.
% When the state's timer elapses, the resulting event
% triggers a transition to "OffState".
sma = AddState(sma, 'Name', 'OnState', ...  
    'Timer', 1,...          % Sets the internal timer of "On state" to 1 second.
    'StateChangeConditions', {'Tup', 'OffState'},...  
    'OutputActions', {'PWM1', 255}); % Outputs for "On state". PWM1 sets Port 1's
                             % PWM-dimmed LED to max brightness (range = 0-255).

% Next add a new state called "OffState" to the description.
sma = AddState(sma, 'Name', 'OffState', ...
    'Timer', 1,...
    'StateChangeConditions', {'Tup', 'OnState'},...
    'OutputActions', {'PWM1', 0});

Additional example Bpod state machine descriptions are given here.

Also see the State Machine Creation page for NewStateMachine() and AddState() function documentation.