Ashley Mills / MMA8452

Library for driving the MMA8452 accelerometer over I2C

Dependents:   MMA8452_Test MMA8452_Demo Dualing_Tanks IMU-Controlled_MP3_Player ... more

Here is a simple example:

#include "mbed.h"
#include "MMA8452.h"

int main() {
   Serial pc(USBTX,USBRX);
   pc.baud(115200);
   double x = 0, y = 0, z = 0;

   MMA8452 acc(p28, p27, 40000);
   acc.setBitDepth(MMA8452::BIT_DEPTH_12);
   acc.setDynamicRange(MMA8452::DYNAMIC_RANGE_4G);
   acc.setDataRate(MMA8452::RATE_100);
   
   while(1) {
      if(!acc.isXYZReady()) {
         wait(0.01);
         continue;
      }
      acc.readXYZGravity(&x,&y,&z);
      pc.printf("Gravities: %lf %lf %lf\r\n",x,y,z);
   }
}

An easy way to test that this actually works is to run the loop above and hold the MMA8452 parallel to the ground along the respective axis (and upsidedown in each axis). You will see 1G on the respective axis and 0G on the others.

Files at this revision

API Documentation at this revision

Revision 16:d6dde2318edc, committed 2014-03-05

Comitter:
ashleymills
Date:
Wed Mar 05 16:47:13 2014 +0000
Parent:
15:7620a11149b8
Child:
17:6e4232c421c0
Commit message:
Added data ready query commands for each independent axes.

Changed in this revision

MMA8452.cpp Show annotated file Show diff for this revision Revisions of this file
MMA8452.h Show annotated file Show diff for this revision Revisions of this file 
--- a/MMA8452.cpp	Wed Mar 05 15:36:03 2014 +0000
+++ b/MMA8452.cpp	Wed Mar 05 16:47:13 2014 +0000
@@ -121,14 +121,31 @@
    );
 }
 
-int MMA8452::isXYZReady() {
+char MMA8452::getMaskedRegister(int reg, char mask) {
    char rval = 0;
-   if(readRegister(MMA8452_STATUS,&rval)) {
+   if(readRegister(reg,&rval)) {
       return 0;
    }
-   return (rval&MMA8452_STATUS_ZYXDR_MASK);
+   return (rval&mask);
+}
+
+int MMA8452::isXYZReady() {
+   return getMaskedRegister(MMA8452_STATUS,MMA8452_STATUS_ZYXDR_MASK)>0;
+}
+
+int MMA8452::isXReady() {
+   return getMaskedRegister(MMA8452_STATUS,MMA8452_STATUS_XDR_MASK)>0;
 }
- 
+
+int MMA8452::isYReady() {
+   return getMaskedRegister(MMA8452_STATUS,MMA8452_STATUS_YDR_MASK)>0;
+}
+
+int MMA8452::isZReady() {
+   return getMaskedRegister(MMA8452_STATUS,MMA8452_STATUS_ZDR_MASK)>0;
+}
+
+
 int MMA8452::getDeviceID(char *dst) {
    return readRegister(MMA8452_WHO_AM_I,dst);
 }

--- a/MMA8452.h	Wed Mar 05 15:36:03 2014 +0000
+++ b/MMA8452.h	Wed Mar 05 16:47:13 2014 +0000
@@ -106,6 +106,9 @@
 
 // status masks and shifts
 #define MMA8452_STATUS_ZYXDR_MASK 0x08
+#define MMA8452_STATUS_ZDR_MASK 0x04
+#define MMA8452_STATUS_YDR_MASK 0x02
+#define MMA8452_STATUS_XDR_MASK 0x01
  
 class MMA8452         
 {        
@@ -244,6 +247,7 @@
       int twelveBitToSigned(char *buf);
       int eightBitToSigned(char *buf);
       double convertCountToGravity(int count, int countsPerG);
+      char getMaskedRegister(int reg, char mask);
     
       I2C _i2c;
       int _frequency;