boost::statechart ---posting a "serial timeout" event

Question

I've been using boost's asynchronous statechart to write a program. In this program I communicate with another device using an asynchronous serial port. I have a state that waits for a confirmation from the device over the serial port and then posts a "confirmation received" event. This works well but, I would also like to implement a "timeout" event.

In previous programs I had been using switch case statements for my state machines where I had code that could be run each time the loop was run. This meant I could run code and check if I should change state due to something timing out. Like this:

while(1){
    switch (state){
        case 0:{
            sendMessage();
            state = 1;
            sendTime = boost::chrono::steady_clock::now();
        }
        break;
        case 1:{
            if (isConfirmationReceived()){
                // do something
                state = 2;
            }
            else if (boost::chrono::steady_clock::now() > sendTime + boost::chrono::duration<double>(WAIT_LENGTH)){
                //raise a time out error
                state = 3;
            }
        }
        break;
        // etc etc

    }
}

How would I implement something like this using boost::StateChart? Should i be thinking about this a completely different way?

score 0 · Answer 1 · answered Jun 28 '13 at 18:00

I don't know if it is best practice but I have solved this problem by sending my SM EvTick events periodically (1ms or something) and handling the event in a super state. You can also add ClearTimeout() SetTimeout() and DisableTimeout() member functions and access them like this:

context< TimeoutSuperState >().SetTimeout(1000);

you can let the superstate transition to an error state on timeout or post an EvOnTimeout to the SM which can be handled differently depending on state.

boost::statechart ---posting a "serial timeout" event

1 Answers1