Diff: main.cpp

Revision:

5:0dd98c2ac767

Parent:

4:75ad475aff41

--- a/main.cpp	Mon Feb 04 16:12:23 2019 +0000
+++ b/main.cpp	Thu Feb 14 23:01:53 2019 +0000
@@ -1,8 +1,5 @@
 // Lab 3 Example Program 2
 // -----------------------
-// Periodically write to the AnalogOut to create a sine wave
-// Alternate between two fixed frequencies every 5 sec
-// 
 // This code uses the Ticker API to create a periodic interrupt
 // Devices used in this way must not call locks; a variant of 
 //   the AnalogOut device w/o locking is created for this.
@@ -27,27 +24,83 @@
 };
 // --------------------------
 
-Ticker tick ;          // Creates periodic interrupt
-AnalogOut_unsafe ao(PTE30) ;  // Analog output
+Ticker tick ;                                                                   // Creates periodic interrupt
+AnalogOut_unsafe ao(PTE30) ;                                                    // Analog output
+AnalogIn ain(A0) ;                                                              // Analog input
 
 // Function called periodically
 // Write new value to AnalogOut 
-volatile int index = 0 ; // index into array of sin values
+volatile int index = 0 ;                                                        // index into array of sin values
 void writeAout() {
     ao.write_u16(sine[index]) ;
     index = (index + 1) % 64 ;   
 }
 
+EventQueue queue;                                                               // creates an event queue, to call read ADC
+
+Serial pc(USBTX, USBRX);                                                        // tx, rx, for debugging
+
+// This thread runs the event queue
+Thread eventThread ;
+
+// Message type
+typedef struct {
+  uint16_t analog;                                                              /* Analog input value */
+} message_t;
+
+// Mail box
+Mail<message_t, 3> mailbox;
+
+// Function called every 10ms to read ADC
+// Average using a low pass filter  
+// Every 10th value is sent to mailbox
+volatile int samples = 0 ;
+volatile uint16_t smoothed = 0 ; 
+
+void readA0() {
+    
+    smoothed = (smoothed >> 1) + (ain.read_u16() >> 1) ;
+    samples++ ;    
+    
+    if (samples == 10) {
+        // send to thread
+        message_t *mess = mailbox.alloc() ;                                     // may fail but does not block
+        if (mess) {
+            mess->analog = smoothed ;
+            mailbox.put(mess);                                                  // fails but does not block if full
+        }  
+        samples = 0;
+    }           
+}
+
 // Control the frequency of updates
 //   Alternative between two frequencies      
 int main() {
     int update_us = 1000 ; // 1ms
+    int volts = 0 ;
+    int timeDelay = 0;
+    int frequency = 0;
+    
+    // Start the event queue
+    eventThread.start(callback(&queue, &EventQueue::dispatch_forever));
+    
+    // call the readA0 function every 10ms 
+    queue.call_every(10, readA0) ; 
+    
     while (true) {
-        tick.attach_us(callback(&writeAout), update_us); // setup ticker to write to AnalogOut
-        wait(30.0) ; // wait 30 sec 
-        update_us = 2000 ; // 2ms
-        tick.attach_us(callback(&writeAout), update_us); // setup ticker to write to AnalogOut
-        wait(30.0) ; // wait 30 sec 
-        update_us = 1000 ; // 1ms
+        osEvent evt = mailbox.get(); // wait for mail 
+        
+        if (evt.status == osEventMail) {
+            message_t* mess = (message_t*)evt.value.p ;
+            volts = (mess->analog * 330) / 0xffff ;
+            mailbox.free(mess) ;                                                // free the message space      
+        }
+        
+        frequency = (1+volts*49/329);                                           // Freq Range: 1~50Hz. V = maximum voltage of ADC
+        timeDelay = 1000000/(frequency*64);                                     // Time is in microseconds  
+        
+        update_us = timeDelay ; 
+        tick.attach_us(callback(&writeAout), update_us);                        // setup ticker to write to AnalogOut
+        
     }
 }