Diff: main.cpp

Revision:

0:319e7e166ef4

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Fri Oct 14 19:30:56 2022 +0000
@@ -0,0 +1,84 @@
+#include "mbed.h"
+#include "PinDetect.h"
+//Lab 3 Part 1
+//See http://makeatronics.blogspot.com/2013/02/efficiently-reading-quadrature-with.html
+//for a detailed explanation of the RPG encoder counting algorithm
+//uses Sparkfun RPG with RGB led on breakout board (#15141,11722,10597)
+//place RPG PCB across a breadboard power bus strip for easier pin hookup!
+InterruptIn RPG_A(p14,PullUp);//encoder A and B pins/bits use interrupts
+InterruptIn RPG_B(p15,PullUp);
+PinDetect RPG_PB(p16); //encode pushbutton switch "SW" on PCB
+//PWM setup for RGB LED in enocder
+PwmOut red(p21);//"R" pin
+PwmOut blue(p23);//"G" pin
+PwmOut green(p22);//"B" pin
+//Note: also tie RPG PCB "C" pin to ground, "+" pin to 3.3
+//mbed status leds
+DigitalOut ledPB(LED1);
+DigitalOut red_adjust_mode(LED2);
+DigitalOut green_adjust_mode(LED3);
+DigitalOut blue_adjust_mode(LED4);
+//Serial pc(USBTX,USBRX);
+volatile int old_enc = 0;
+volatile int new_enc = 0;
+volatile int enc_count = 0;
+int current_state = 0;
+//Instead of a slow 16 case statement use a faster table lookup of truth table
+//index table with (previous encoder AB value<<2 | current current encoder AB value) 
+//to find -1(CCW),0,or 1(CW) change in count each time a bit changes state
+//Always want Interrupt routines to run fast!
+//const puts data in read only Flash instead of RAM
+const int lookup_table[] = {0,-1,1,0,1,0,0,-1,-1,0,0,1,0,1,-1,0};
+//Encoder bit change interrupt service routine
+//called whenever one of the two A,B encoder bits change state
+void Enc_change_ISR(void)
+{
+    new_enc = RPG_A<<1 | RPG_B;//current encoder bits
+    //check truth table for -1,0 or +1 added to count
+    enc_count = enc_count + lookup_table[old_enc<<2 | new_enc];
+    old_enc = new_enc;
+}
+//debounced RPG pushbutton switch callback
+int state_change(void){
+    return (current_state + 1) % 3;
+}
+void PB_callback(void)
+{
+    if (!ledPB.read()) {
+        current_state = state_change();
+    }
+    //ledPB= !ledPB;
+}
+int main()
+{
+//turn off built-in RPG encoder RGB led
+    red = 1.0;//PWM value 1.0 is "off", 0.0 is full "on"
+    green = 1.0;
+    blue = 1.0;
+//current color adjust set to red
+    red_adjust_mode = 1;
+//debounce RPG center pushbutton
+    RPG_PB.mode(PullDown);
+    RPG_PB.attach_deasserted(&PB_callback);
+    RPG_PB.setSampleFrequency();
+// generate an interrupt on any change in either encoder bit (A or B)
+    RPG_A.rise(&Enc_change_ISR);
+    RPG_A.fall(&Enc_change_ISR);
+    RPG_B.rise(&Enc_change_ISR);
+    RPG_B.fall(&Enc_change_ISR);
+    while (true) {
+        // Scale/limit count to 0..100
+        if (enc_count>100) enc_count = 100;
+        if (enc_count<0) enc_count = 0;
+        if (current_state == 0) {
+            red = 1.0 - enc_count / 100.0;
+        } else if (current_state == 1) {
+            green = 1.0 - enc_count / 100.0;
+        } else {
+            blue = 1.0 - enc_count / 100;
+        }
+        //green = 1.0 - enc_count/100.0;
+//        pc.printf("%D\n\r",enc_count);
+    }
+}
+ 
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