Revision 0:581963db97d8, committed 2013-06-16

Comitter:

robt

Date:

Sun Jun 16 15:19:06 2013 +0000

Commit message:

by Rob Toulson and Tim Wilmshurst from textbook "Fast and Effective Embedded Systems Design: Applying the ARM mbed"

Changed in this revision

diff -r 000000000000 -r 581963db97d8 main.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun Jun 16 15:19:06 2013 +0000
@@ -0,0 +1,36 @@
+/* Program Example 11.3 Delay / Echo Effect
+                                                                */
+#include "mbed.h"
+AnalogIn Ain(p15);              //object definitions
+AnalogOut Aout(p18);
+AnalogIn delay_pot(p16);
+AnalogIn feedback_pot(p17);
+Ticker s20khz_tick; 
+void s20khz_task(void);         // function prototypes
+#define MAX_BUFFER 14000        // max data samples
+signed short data_in;           // signed allows positive and negative
+unsigned short data_out;        // unsigned just allows positive values
+float delay=0;
+float feedback=0;
+signed short buffer[MAX_BUFFER]={0}; // define buffer and set values to 0 
+int i=0;
+
+//main program start here
+int main() {
+  s20khz_tick.attach_us(&s20khz_task,50);  
+}
+// function 20khz_task
+void s20khz_task(void){
+  data_in=Ain.read_u16()-0x7FFF;           // read data and normalise
+  buffer[i]=data_in+(buffer[i]*feedback);  // add data to buffer data
+  data_out=buffer[i]+0x7FFF;               // output buffer data value
+  Aout.write_u16(data_out);                // write output
+  if (i>(delay)){                          // if delay loop has completed
+    i=0;                              // reset counter
+    delay=delay_pot*MAX_BUFFER;       // calculate new delay buffer size
+    feedback=(1-feedback_pot)*0.9;    // calculate feedback gain value
+  }else{
+    i=i+1;                            // otherwise increment delay counter
+  }  
+}
+

diff -r 000000000000 -r 581963db97d8 mbed.bld
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Sun Jun 16 15:19:06 2013 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/b3110cd2dd17
\ No newline at end of file