main.cpp

00001 #include "mbed.h" // import of mbed library (required)
00002 /*******************************************************************************
00003 
00004   EXAMPLE DESCRIPTION
00005 
00006   Uses two buttons connected to PA_0 - plus and PA_1 - minus with internal pull 
00007   up resistors. On PA_8 is PWM output with variable duty cycle (DC) and frequncy 
00008   of 500 Hz.DC can be changed true buttons. On press of button DC is incremented 
00009   or decremented by 0.01. Interrupt is attached to falling edge on appropriate
00010   pin and process of incrementation/decrementation is driven throu this
00011   interrupt. Programm also demonstrates auto incrementation/decrementation while
00012   button is pressed for longer than 1 s. After button is pressed timer is 
00013   started. Ticker periodically  (every 10 ms) calls function that checks timer
00014   value. If the timer had counted more than 1 s, It is stopped and auto 
00015   incementation/decrementation is stared (+-0.01 every 500 ms). After button
00016   release auto incementation/decrementation is stopped and timer reset. 
00017   Programm is written in way, that there can NOT be simultaneously active both
00018   auto incrementation and decrementation. Note that there are also prints to 
00019   UART to check states of buttons and change of DC.
00020   
00021 *******************************************************************************/
00022 
00023 InterruptIn buttonPlus(PA_0); // deffition of interrupt
00024 InterruptIn buttonMinus(PA_1); // deffition of interrupt
00025 
00026 PwmOut PWM(PA_8); // definition of PWM pin
00027 
00028 Timer tim; // Timer definition
00029 
00030 Ticker tick; // Ticker definition
00031 
00032 bool autoIncrement=false; // true - do autoincrement
00033                           // false - do not autoincrement
00034 
00035 bool plus=true; // true -  auto increment
00036                 // false - auto decrement
00037 
00038 // called after falling edge on PA_0
00039 // starts timer for auto increment check
00040 // increments DC
00041 void pressedPlus() {
00042     tim.start(); // start Timer
00043     plus=true; // incrementation
00044     if (PWM.read()+0.01 <= 1) {
00045         PWM.write(PWM.read()+0.01); 
00046         printf("Presed plus button. DC: %f.\n",PWM.read());
00047     }else{
00048         PWM.write(1);
00049         printf("Presed plus button. Already maximum DC.\n");
00050     }
00051 }
00052 
00053 // called after rising edge on PA_0
00054 // stops and resets auto increment timer
00055 // stops auto increment
00056 void releasedPlus(){
00057     tim.stop();
00058     tim.reset();
00059     autoIncrement=false;
00060     printf("Plus button released.\n");
00061 }
00062 
00063 // called after falling edge on PA_1
00064 // starts timer for auto decrement check
00065 // decrements DC
00066 void pressedMinus() {
00067     tim.start(); // start Timer
00068     plus=false; // decrementation
00069     if (PWM.read()-0.01 >= 0) {
00070         PWM.write(PWM.read()-0.01);
00071         printf("Presed minus button. DC: %f\n",PWM.read());
00072     }else{
00073         PWM.write(0);
00074         printf("Presed minus button. Already minimum DC.\n");
00075     }
00076 }
00077 
00078 // called after rising edge on PA_1
00079 // stops and resets auto decrement timer
00080 // stops auto decrement
00081 void releasedMinus(){
00082     tim.stop();
00083     tim.reset();
00084     autoIncrement=false;
00085     printf("Minus button released.\n");
00086 }
00087 
00088 
00089 // checks timer value
00090 // if > 1 s starts auto incerement/decrement
00091 void checkTimer(){
00092     if(tim.read_ms()>1000){
00093         tim.stop();
00094         autoIncrement=true;
00095     }    
00096 }
00097 
00098 int main()
00099 {
00100         
00101     // Set PWM
00102     PWM.period_ms(2); // 500 Hz
00103     PWM.write(0); // duration of active pulse
00104     
00105     // Set buttons interrupts
00106     buttonPlus.fall(&pressedPlus);
00107     buttonMinus.fall(&pressedMinus);
00108     buttonPlus.rise(&releasedPlus);
00109     buttonMinus.rise(&releasedMinus);
00110     
00111     // internal pull ups
00112     buttonPlus.mode(PullUp);
00113     buttonMinus.mode(PullUp);
00114     
00115     // set ticker interrupt
00116     tick.attach(&checkTimer,0.01);
00117     
00118     while (1) {
00119         // check if auto increment/decrement
00120         if(autoIncrement && plus && PWM.read()+0.01 <= 1){
00121             PWM.write(PWM.read()+0.01);
00122             printf("Autoincrement. DC: %f.\n",PWM.read());
00123         }
00124         else if(autoIncrement && !plus && PWM.read()-0.01 >= 0){
00125             PWM.write(PWM.read()-0.01);
00126             printf("Autodecrement. DC: %f.\n",PWM.read());
00127         }
00128         wait_ms(500);
00129     }
00130 }