This article provides an alternate C language state machine implementation based on the ideas presented within the article “The article is not a tutorial on the best design decomposition practices for software state machines. Event data is a single Once the state has completed execution, the event data is considered used up and must be deleted. | Finite State Machines - Theory SWRP161 Finite State Machines - Theory 2 C programming fundamentals • Arrays • Pointers • Structures • Time delays Develop debugging techniques such as • Watch windows • Breakpoints • Heart beats Solve problems with finite state machines • States, tables, graphs, input, outputs The motor control events to be exposed to the client software will be as follows:These events provide the ability to start the motor at whatever speed desired, which also implies changing the speed of an already moving motor. I'm currently unsupervised, I know it freaks me out too!#define SM_Event(_smName_, _eventFunc_, _eventData_) \

This run to completion model provides a multithread-safe environment for the state transitions. The The last detail to attend to are the state transition rules. Abstract state machine structure struct state_machine_t { uint32_t Event; //!< Pending Event for state machine const state_t* State; //!< State of state machine. This process continues until the state machine is no longer generating internal events, at which time the original external event function call returns.

Using C, you have to work a bit harder to accomplish similar behavior. Every state function returns the code, you lookup state transition table by state and return code to find the next state and then just execute it. For example, In POS device we have read function which when you pressed the key, swipe the card or insert the card then it returns relevant event value. For an ignored event, no state executes.

In the below section, I am describing some ways to implement the state machine using the function pointer and lookup table.We will create a 2D array containing the function pointers. The answer is the transition map. #define END_TRANSITION_MAP(_smName_, _eventData_) \

The state transition is assumed to be valid. A new state causes a transition to a new state where it is allowed to execute. Simple enough. We will then illustrate the concept by applying the implemented FSM to two different scenarios. This is the state the state machine currently occupies. Interestingly, that old article is still available and (at the time of writing this article) the #1 hit on Google when searching for C++ state machine.

If you want you can reverse the procedure that means you can check the event first and after that checks the states.A lookup table is also a very good technique to implement the state machine.

This C language state machine supports multiple state machine objects (or instances) instead of having a single, static state machine implementation. How does the state machine know what transitions should occur? Events, on the other hand, are the stimuli, which cause the state machine to move, or transition, between states.To take a simple example, which I will use throughout this article, let's say we are designing motor-control software. It depends on a requirement that checks first states or the event.In the below sample code, I am verifying the states first and after that checks the triggered event. A box denotes a state and a connecting arrow indicates the event transitions. You could check for both valid internal and external event transitions, but in practice, this just takes more storage space and generates busywork for very little benefit. A finite state machine in C is one of the popular design patterns for the embedded system. On the basis of this event value, you call the relevant function, like when you swipe the card in POS device then an event value (MAG_CARD_EVENT) return by the read function.It is not vary for program but vary with device, each device have their own API to read the events.From where can I learn these type of embedded programming?There are a lot of magazines which is published the article regarding the Finite state machine.What if we have timer based events.