Revision 5:2d14600116fc, committed 2013-03-10

Comitter:

JoKer

Date:

Sun Mar 10 04:34:03 2013 +0000

Parent:

4:c4d879a39775

Commit message:

Added Double Tap Detection functionality

Changed in this revision

diff -r c4d879a39775 -r 2d14600116fc MMA8451Q.cpp
--- a/MMA8451Q.cpp	Fri Oct 12 11:35:07 2012 +0000
+++ b/MMA8451Q.cpp	Sun Mar 10 04:34:03 2013 +0000
@@ -18,8 +18,21 @@
 
 #include "MMA8451Q.h"
 
+#define INT_SOURCE        0x0C 
 #define REG_WHO_AM_I      0x0D
-#define REG_CTRL_REG_1    0x2A
+#define HP_FILTER_CUTOFF  0x0F 
+#define PULSE_CFG         0x21 
+#define PULSE_SRC         0x22 
+#define PULSE_THSX        0x23 
+#define PULSE_THSY        0x24 
+#define PULSE_THSZ        0x25 
+#define PULSE_TMLT        0x26 
+#define PULSE_LTCY        0x27 
+#define PULSE_WIND        0x28 
+#define REG_CTRL_REG_1    0x2A 
+#define CTRL_REG2         0x2B
+#define CTRL_REG4         0x2D 
+#define CTRL_REG5         0x2E 
 #define REG_OUT_X_MSB     0x01
 #define REG_OUT_Y_MSB     0x03
 #define REG_OUT_Z_MSB     0x05
@@ -41,6 +54,7 @@
 }
 
 float MMA8451Q::getAccX() {
+//divide by 4096 b/c MMA output is 4096 counts per g so this f outputs accelorometer value formatted to g (gravity)
     return (float(getAccAxis(REG_OUT_X_MSB))/4096.0);
 }
 
@@ -70,12 +84,72 @@
     return acc;
 }
 
+void MMA8451Q::setDoubleTap(void){
+//Implemented directly from Freescale's AN4072 
+//Added to MMA8451Q lib
+
+    uint8_t CTRL_REG1_Data;
+//    int adds;
+   uint8_t data[2] = {REG_CTRL_REG_1, 0x08};
+    
+    //400 Hz, Standby Mode
+    writeRegs(data,2);
+    
+    //Enable X, Y and Z Double Pulse with DPA = 0 no double pulse abort    
+    data[0]=PULSE_CFG;data[1]=0x2A;
+    writeRegs(data,2);
+    
+    //SetThreshold 3g on X and Y and 5g on Z
+    //Note: Every step is 0.063g
+    //3 g/0.063g = 48 counts
+    //5g/0.063g = 79 counts
+    data[0]=PULSE_THSX;data[1]=0x30;
+    writeRegs(data,2);//Set X Threshold to 3g 
+    data[0]=PULSE_THSY;data[1]=0x30;
+    writeRegs(data,2);//Set Y Threshold to 3g 
+    data[0]=PULSE_THSZ;data[1]=0x4F;
+    writeRegs(data,2);//Set Z Threshold to 5g
+
+    //Set Time Limit for Tap Detection to 60 ms LP Mode
+    //Note: 400 Hz ODR, Time step is 1.25 ms per step
+    //60 ms/1.25 ms = 48 counts 
+    data[0]=PULSE_TMLT;data[1]=0x30;
+    writeRegs(data,2);//60 ms
+    
+    //Set Latency Time to 200 ms
+    //Note: 400 Hz ODR LPMode, Time step is 2.5 ms per step 00 ms/2.5 ms = 80 counts
+    data[0]=PULSE_LTCY;data[1]=0x50;
+    writeRegs(data,2);//200 ms
+    
+    //Set Time Window for second tap to 300 ms
+    //Note: 400 Hz ODR LP Mode, Time step is 2.5 ms per step
+    //300 ms/2.5 ms = 120 counts
+    data[0]=PULSE_WIND;data[1]=0x78;
+    writeRegs(data,2);//300 ms
+    
+    //Route INT1 to System Interrupt
+    data[0]=CTRL_REG4;data[1]=0x08;
+    writeRegs(data,2);//Enable Pulse Interrupt in System CTRL_REG4
+    data[0]=CTRL_REG5;data[1]=0x08; 
+    writeRegs(data,2);//Route Pulse Interrupt to INT1 hardware Pin CTRL_REG5
+
+    //Set the device to Active Mode
+    readRegs(0x2A,&CTRL_REG1_Data,1);//Read out the contents of the register 
+    CTRL_REG1_Data |= 0x01; //Change the value in the register to Active Mode.
+    data[0]=REG_CTRL_REG_1; 
+    data[1]=CTRL_REG1_Data;
+    writeRegs(data,2);//Write in the updated value to put the device in Active Mode
+}
+
+
 void MMA8451Q::readRegs(int addr, uint8_t * data, int len) {
     char t[1] = {addr};
     m_i2c.write(m_addr, t, 1, true);
     m_i2c.read(m_addr, (char *)data, len);
 }
 
+
+
 void MMA8451Q::writeRegs(uint8_t * data, int len) {
     m_i2c.write(m_addr, (char *)data, len);
 }

diff -r c4d879a39775 -r 2d14600116fc MMA8451Q.h
--- a/MMA8451Q.h	Fri Oct 12 11:35:07 2012 +0000
+++ b/MMA8451Q.h	Sun Mar 10 04:34:03 2013 +0000
@@ -97,6 +97,55 @@
    * @param res array where acceleration data will be stored
    */
   void getAccAllAxis(float * res);
+  
+  /** JK
+  * Setup Double Tap detection
+ 
+ 
+Example:
+
+#include "mbed.h"
+#include "MMA8451Q.h"
+
+#define MMA8451_I2C_ADDRESS (0x1d<<1)
+#define ON  0
+#define OFF !ON
+
+//Setup the interrupts for the MMA8451Q
+InterruptIn accInt1(PTA14);
+InterruptIn accInt2(PTA15);//not used in this prog but this is the other int from the accelorometer
+
+uint8_t togstat=0;//Led status
+DigitalOut bled(LED_BLUE);
+
+
+void tapTrue(void){//ISR
+    if(togstat == 0){
+        togstat = 1;
+        bled=ON;
+    } else {
+        togstat = 0;
+        bled=OFF;
+    }
+        
+}
+
+
+int main(void) {
+
+    MMA8451Q acc(PTE25, PTE24, MMA8451_I2C_ADDRESS);//accelorometer instance
+  
+    acc.setDoubleTap();//Setup the MMA8451Q to look for a double Tap
+    accInt1.rise(&tapTrue);//call tapTrue when an interrupt is generated on PTA14
+    
+    while (true) {
+    //Interrupt driven so nothing in main loop
+    }
+}
+
+
+  */
+  void setDoubleTap(void);
 
 private:
   I2C m_i2c;