Revision 0:de78c543d4ed, committed 2013-06-16

Comitter:

robt

Date:

Sun Jun 16 15:37:57 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 de78c543d4ed main.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun Jun 16 15:37:57 2013 +0000
@@ -0,0 +1,47 @@
+/* Program Example: 13.2 Open Loop Compass 
+                                                               */
+#include "mbed.h"
+//***** mbed objects *****
+I2C compass(p28, p27);         // sda, scl
+PwmOut PWM(p25);
+AnalogIn Ain(p20);
+Serial pc(USBTX, USBRX);        // tx, rx
+Ticker s100hz_tick;             // 100 Hz (10ms) ticker
+Ticker s5hz_tick;               // 5 Hz (200ms) ticker
+//***** variables *****
+const int addr = 0x42;          // define the I2C write Address
+char cmd[3];
+float pos;                      // measured position
+float ctrlval;                  // PWM control value
+//***** function prototypes *****
+void s100hz_task(void);         // 100 Hz task
+void s5hz_task(void);           // 5 Hz task
+//***** main code *****
+int main() {
+  // initialise and setup data
+  PWM.period(0.02);
+  cmd[0] = 0x47;                 // 'G' write to RAM address
+  cmd[1] = 0x74;                 // Operation mode register address
+  cmd[2] = 0x72;                 // Op mode = 20H, S/R, continuous 
+  compass.write(addr,cmd, 3);    // Send operation
+  s100hz_tick.attach(&s100hz_task,0.01);     // attach 100 Hz task              
+  s5hz_tick.attach(&s5hz_task,0.2);          // attach 5 Hz task 
+  while(1){
+  // loop forever
+  }
+}
+
+//***** function 100hz_task *****
+void s100hz_task(void) {
+  compass.read(addr, cmd, 2);     // read the two-byte compass data
+  pos = 0.1 * ((cmd[0] << 8) + cmd[1]);        //convert to degrees
+    if (pos>180)
+      pos=pos-360;                            // convert to ±180deg
+  ctrlval=Ain;          // set control value (also try ctrlval=Ain/4)
+  PWM=ctrlval;          // output control value to PWM
+}
+
+//***** function 5hz_task *****
+void s5hz_task(void) {
+  pc.printf("deg = %.1f    PWM = %.4f\n", pos, ctrlval);
+}

diff -r 000000000000 -r de78c543d4ed mbed.bld
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Sun Jun 16 15:37:57 2013 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/b3110cd2dd17
\ No newline at end of file