State Machines

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from http:c-faq.comdeclrecurfuncp.html Mod by JDN Simple efficent way to model state machines in C

typedef void (pFunc)(); for typecast for calling function

States – you need this forward dcl for the compiler and calling

led-off –> led-on  — | ^ —  —  —  —  —  — -| all driven from main (or here setup fct)

void led_on(); as name indicates … void led_off();

void led_on() { printf(“on
”); return (void )led_off; next state }

void led_off() { printf(“off
”); return (void )led_on; next state }

void main() {

pFunc statefunc = led_on, oldfunc = led_on;

while(1) { oldfunc = statefunc; if you want to see the previous state - line can be omitted statefunc = (pFunc)(*statefunc)(); nice thing of design is you can easily track all state changes bq you will pass by here :-) }

return ; should not get here }

from http:c-faq.comdeclrecurfuncp.html Mod by JDN for Arduino Simple efficent way to model state machines in C

typedef void (pFunc)(); for typecast for calling function

States – you need this forward dcl for the compiler and calling

led-off –> led-on  — | ^ —  —  —  —  —  — -| all driven from main (or here setup fct)

void led_on(); as name indicates … void led_off();

void *led_on() { digitalWrite(13,HIGH); delay(1000); sleep for a second

return (void *)led_off; next state }

void *led_off() { digitalWrite(13,LOW); delay(1000); sleep for a second

return (void *)led_on; next state }

void setup() {

pinMode(13,OUTPUT);

}

pFunc statefunc = led_on, oldfunc = led_on;

/ The idea Variable named statefunc(aka state) holds address of next function to be called when you leave a function you simply return reference to enxt function or state to be called This address is stored in variable statefunc. The code loops and call again and now we call next state * Instead of having code in loop you could have it every where like

while (1) { oldfunc = statefunc; just if you want to see the previous state - debugging !!! statefunc = (pFunc)(statefunc)(); } void loop() { oldfunc = statefunc; / just if you want to see the previous state - debugging !!! statefunc = (pFunc)(statefunc)(); }

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(C) Jens Dalsgaard Nielsen
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