Revision 0:5307f49cd305, committed 2017-02-01

Comitter:

WilliamMarshQMUL

Date:

Wed Feb 01 13:38:02 2017 +0000

Child:

1:284229960d6a

Commit message:

First version

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Wed Feb 01 13:38:02 2017 +0000
@@ -0,0 +1,62 @@
+// Lab 3 Example Program 2
+// -----------------------
+// Periodically write to the AnalogOut to create a sine wave
+// Alternate between two fixed frequencies every 5 sec
+//
+// THIS VERSION HAS DEBUGGING CODE USING THE SERIAL PORT
+
+#include "mbed.h"
+#include "rtos.h"
+#include "sineTable.h"
+
+Ticker tick ;          // Creates periodic interrupt
+AnalogOut ao(PTE30) ;  // Analog output
+
+// --- following code for debugging ---
+Thread debugT ;
+Serial pc(USBTX, USBRX); // tx, rx, useful for debugging
+
+// Put a simple reprsentation of the sine wave
+//  to the serial output. ONLY at low frequency
+void debug(int index) {
+    int sine4 = sine[index] >> 11 ; // get top 5 bits
+    pc.putc('*') ;
+    while (sine4--) pc.putc('*') ;
+    pc.putc('\n') ;
+    //pc.putc('\r') ;  
+}
+
+volatile int index = 0 ; // this variable is not just for debugging!!
+
+void debugCallback() {
+    while (true) {
+        Thread::signal_wait(0x1) ;
+        debug(index) ;  // there is a race condition here
+    }
+}
+// ---- end of debugging code ---------
+
+// Function called every periodically
+// Write new value to AnalogOut 
+void writeAout() {
+    ao.write_u16(sine[index]) ;
+    debugT.signal_set(0x1) ; // DEBUGGING low frequency only
+    index = (index + 1) % 64 ;   
+}
+
+// Control the frequency of updates
+//   Alternative between two frequencies      
+int main() {
+    int update_us = 100000 ; // 100ms
+    debugT.start(&debugCallback) ;
+    while (true) {
+        pc.printf("Update at 64 x 100ms giving about 0.15Hz\n");
+        tick.attach_us(callback(&writeAout), update_us); // setup ticker to write to AnalogOut
+        Thread::wait(30000) ; // wait 30 sec - 30000ms
+        update_us = 150000 ; // 150ms
+        pc.printf("Update at 64 x 150ms giving about 0.1Hz\n");
+        tick.attach_us(callback(&writeAout), update_us); // setup ticker to write to AnalogOut
+        Thread::wait(30000) ; // wait 30 sec - 30000ms
+        update_us = 100000 ; // 100ms
+    }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-rtos.lib	Wed Feb 01 13:38:02 2017 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed-rtos/#58563e6cba1e

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Wed Feb 01 13:38:02 2017 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/ad3be0349dc5
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sineTable.h	Wed Feb 01 13:38:02 2017 +0000
@@ -0,0 +1,15 @@
+// Look up table for a sine wave as 16 bits
+// Note that it is possible to construct the full period from 
+//   the first quarter, but the code is more complex
+//
+// These number were calcuated using a spreadsheet 
+const uint16_t sine[] = {
+    32768, 35980, 39161, 42280, 45308, 48215, 50973, 53556, 
+    55938, 58098, 60014, 61667, 63042, 64125, 64906, 65378, 
+    65535, 65378, 64906, 64125, 63042, 61667, 60014, 58098,
+    55938, 53556, 50973, 48215, 45308, 42280, 39161, 35980,
+    32768, 29556, 26375, 23256, 20228, 17321, 14563, 11980,
+     9598,  7438,  5522,  3869,  2494,  1411,   630,   158, 
+        0,   158,   630,  1411,  2494,  3869,  5522,  7438,
+     9598, 11980, 14563, 17321, 20228, 23256, 26375, 29556
+    } ;
\ No newline at end of file