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 5:b3d0abd97e55, committed 2013-10-16

Comitter:
nherriot
Date:
Wed Oct 16 18:55:16 2013 +0000
Parent:
4:27aa3cd43234
Child:
6:f6bde04bf8be
Child:
7:8aa5123d403f
Commit message:
adding method for getting control reg 1.;

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 Oct 16 16:26:26 2013 +0000
+++ b/MMA8452.cpp	Wed Oct 16 18:55:16 2013 +0000
@@ -57,6 +57,39 @@
 }
 
 
+// Get 'Fast Read Mode' called F_READ. If bit 1 is set '1' then F_READ is active. Fast read will skip LSB when reading xyz
+// resisters from 0x01 to 0x06. When F_READ is '0' then all 6 registers will be read.
+
+int Accelerometer_MMA8452::get_CTRL_Reg1(int& CTRL_Reg)
+{
+{
+    char mcu_address = (MMA8452_ADDRESS<<1);
+    m_i2c.start();
+    if( m_i2c.write( mcu_address & 0xFE) == 0)          // just good practice to force bit 1 to a '0' by ANDing with 0xFE
+    {
+        return 1;                                       // we failed to write the mcu address on the bus to initiate dialogue 
+    }
+    if( m_i2c.write( CTRL_REG_1) == 0) 
+    {
+        return 1;                                       // we failed to write 'status' to the chip
+    }
+    m_i2c.start();
+    if( m_i2c.write( mcu_address | 0x01) == 0)          // this is asking to read the slave mcu address - even though it's a 'write' method!!! Crap API...
+    {
+        return 1;                                       // we failed to request a read from that mcu - this really is just writing the mcu vaule on the bus
+    }
+    CTRL_Reg  = m_i2c.read(0);
+    m_i2c.stop();
+    return 0;
+    
+
+}
+
+
+
+
+}
+
 // Setting the control register bit 1 to true to activate the MMA8452
 int Accelerometer_MMA8452::standby()
 {

--- a/MMA8452.h	Wed Oct 16 16:26:26 2013 +0000
+++ b/MMA8452.h	Wed Oct 16 18:55:16 2013 +0000
@@ -187,6 +187,16 @@
       int standby();
 
  
+       /** get_CTRL_Reg1 the MMA8452 (not required)
+        *   returns 0 for success in activating the chip
+        *   returns 1 for failure in activating the chip
+        *   -currrently no retries or waiting is done, this method tries 1 time the exits.
+        *
+        *   This will return the state of the control register 1. This holds and sets values for auto wake, sleep mode
+        *   output data rate, fast read mode and active/standby. More info on 6.7 of pdf for MMA8452 Freescale doc.
+      */
+      int get_CTRL_Reg1(int& CTRL_Reg); 
+      
       
        /** Initialization of device MMA8452 (required)
         */