Revision 0:0d4a1401a9c5, committed 2012-02-05

Comitter:

hassan_ali

Date:

Sun Feb 05 21:03:49 2012 +0000

Commit message:

this class is not a prefect or complete class containing all features of the MMA7455L accelermoter, but it can be extended later.

Changed in this revision

diff -r 000000000000 -r 0d4a1401a9c5 MMA7455L_SPI.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MMA7455L_SPI.cpp	Sun Feb 05 21:03:49 2012 +0000
@@ -0,0 +1,138 @@
+#include "MMA7455L_SPI.h" 
+
+MMA7455L_SPI :: MMA7455L_SPI (PinName _mosi, PinName _miso, PinName _clk, PinName _cs):_CS(_cs),_spi(_mosi, _miso, _clk)
+{
+    /*initializing the main variables (or data members) of the accelermoter class*/
+    Ax = 0;
+    Ay = 0;
+    Az = 0;
+    sensetivity = 0;
+    _CS = 1; /* just to disable the connection by default, and if we want to enable it _CS = 0 */
+    _spi.format(8,0);
+    _spi.frequency(8000000);
+     set_mode(0x01);
+     set_interrupt_latch_reset_time();
+     //set_offsets(char, char, char); 
+     set_control_1();
+     set_control_2();
+     set_level_detection_thershold_limit_value();
+     set_pulse_detection_thershold_limit_value();
+     set_pulse_duration_value();
+     set_latency_time_value();
+}
+
+signed char MMA7455L_SPI :: read(char adress)
+{
+    signed char value;
+    _CS = 0;
+    _spi.write(READ | (adress << 1) );
+    value = _spi.write(0x00); /*writing a dummy char ito the register while returning the register
+                               content because SPI is an exchange protocol*/
+    _CS = 1;                           
+    return value;
+}
+
+void MMA7455L_SPI :: write(char adress, char content)
+{
+    _CS = 0;
+    _spi.write(WRITE | (adress << 1) );
+    _spi.write(content);
+    _CS = 1;
+}
+
+void MMA7455L_SPI :: set_mode(char reg_mode) /*notice that we operate on measurment mode only*/
+{
+    write(MODE_CONTROL, reg_mode);
+    char g_select_1 = reg_mode & 0x08;
+    char g_select_0 = reg_mode & 0x04;
+    if ( (g_select_1 == 0) && (g_select_0 == 0) ) /*means we are operating on 8g range*/
+    {
+        sensetivity = 16; /*the units are "count/g" */
+    }
+    else if ( (g_select_1 == 0) && (g_select_0 == 1) ) /*means we are operating on 2g range*/
+    {
+        sensetivity = 64;
+    }
+    else if ( (g_select_1 == 1) && (g_select_0 == 0) ) /*means we are operating on 4g range*/
+    {
+        sensetivity = 32;
+    }
+    
+}
+
+void MMA7455L_SPI :: set_range_of_measurment(int GS1, int GS0)
+{
+    char g_select_1 = GS1 << 3;
+    char g_select_0 = GS0 << 2;
+    char reg_mode = g_select_1 | g_select_0;
+    set_mode(reg_mode);
+}
+
+/* these functions may not be useful now, but may be of use if the class is to be extended*/
+
+ void MMA7455L_SPI :: set_interrupt_latch_reset_time(char value)
+ {
+    write(INTERRUPT_LATCH_RESET, value);
+ }
+ 
+ void MMA7455L_SPI :: set_control_1(char value)
+ {
+    write(CONTROL_1, value);
+ }
+ void MMA7455L_SPI :: set_control_2(char value)
+ {
+    write(CONTROL_2, value);
+ }
+ 
+ void MMA7455L_SPI :: set_level_detection_thershold_limit_value(char value)
+ {
+    write(LEVEL_DETECTION_THRESHOLD_LIMIT,value);
+ }
+ 
+ void MMA7455L_SPI :: set_pulse_detection_thershold_limit_value(char value)
+ {
+    write(PULSE_DETECTION_THRESHOLD_LIMIT,value);
+ }
+
+void MMA7455L_SPI :: set_pulse_duration_value(char value)
+{
+    write(PULSE_DURATION_VALUE, value);
+}
+
+void MMA7455L_SPI :: set_latency_time_value(char value)
+{
+    write(LATENCY_TIME_VALUE, value);
+}
+
+void MMA7455L_SPI :: set_offsets (char offx, char offy, char offz)
+{
+    /*this function is not very necessary as the offset values were measured beore and sutracted
+    from the readings in the "update_acceleraton()" function ... if you want to know more info, you
+    can refer to Freescale MMA7455L data sheet page 24, and Freescale application note AN3745, which 
+    describes a procedure for this calibration. */
+}
+
+signed char MMA7455L_SPI :: status()
+{
+    signed char value = 0;
+    value = read(STATUS);
+    return value;
+}
+
+void MMA7455L_SPI :: update_acceleration()
+{
+    signed char x = 0,y = 0,z = 0;
+    if( status() & DATA_READY)  
+    {
+        x = read(X_OUT);
+        Ax = (float)x / sensetivity + 0.1875;
+        
+        y = read(Y_OUT);
+        Ay = (float)y / sensetivity + 0.438;
+        
+        z = read(Z_OUT);
+        Az = (float)z / sensetivity + 1 - 0.562;
+    }
+}
+
+

diff -r 000000000000 -r 0d4a1401a9c5 MMA7455L_SPI.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MMA7455L_SPI.h	Sun Feb 05 21:03:49 2012 +0000
@@ -0,0 +1,80 @@
+/*This class is meant to interface the MMA7455L digital acceleromter with the mbed micro through a SPI interface.
+This class deals mainly with acquiring measurment from the acceleromter, but doesn't deal with pulse detection 
+or interrupts, so it needs to be extended*/
+
+#ifndef MMA7455L_SPI_H
+#define MMA7455L_SPI_H
+
+#include "mbed.h"
+
+/*declaration of the registers of the MMA7455L accelermoter*/
+
+#define X_OUT                                   0x06
+#define Y_OUT                                   0x07
+#define Z_OUT                                   0x08
+#define STATUS                                  0x09
+#define DETECTION_SOURCE_REGISTER               0x0A
+#define X_OFF_LSB                               0x10
+#define X_OFF_MSB                               0x11
+#define Y_OFF_LSB                               0x12
+#define Y_OFF_MSB                               0x13
+#define Z_OFF_LSB                               0x14
+#define Z_OFF_MSB                               0x15
+#define MODE_CONTROL                            0x16
+#define INTERRUPT_LATCH_RESET                   0x17
+#define CONTROL_1                               0x18
+#define CONTROL_2                               0x19
+#define LEVEL_DETECTION_THRESHOLD_LIMIT         0x1A
+#define PULSE_DETECTION_THRESHOLD_LIMIT         0x1B
+#define PULSE_DURATION_VALUE                    0x1C
+#define LATENCY_TIME_VALUE                      0x1D
+
+/*some useful charechters for writing, reading and checking readiness of data*/
+#define READ                                    0x00
+#define WRITE                                   0x80
+#define DATA_READY                              0x01
+
+               
+
+
+ class MMA7455L_SPI{
+ 
+ public: 
+ 
+ float Ax,Ay,Az;
+ MMA7455L_SPI(PinName, PinName, PinName, PinName); /*mosi, miso, clk and cs*/
+ void update_acceleration();
+ void set_range_of_measurment(int GS1, int GS0); /*this function takes two bits, zeros ones
+                                                   and they are used to determine the required char 
+                                                   to be sent to the mode control register*/
+//void set_mode_of_operation(int LSB1, int LSB2);                                                 
+ 
+ 
+ private:
+ 
+ int sensetivity;
+ DigitalOut _CS;
+ SPI _spi;
+ 
+ /*we declare some basic functions for reading data from accelermoter and writing to the accelermoter**/
+ signed char read(char adress);
+ void write(char adress, char content);
+ 
+ /*some basic functions that take a char that controls mode of operation and behaviour of the accelermoter*/
+ void set_mode(char);
+ void set_interrupt_latch_reset_time(char value = 0x03);
+ void set_offsets(char, char, char); 
+ void set_control_1(char value = 0x00);
+ void set_control_2(char value = 0x00);
+ void set_level_detection_thershold_limit_value(char value = 0x2F);
+ void set_pulse_detection_thershold_limit_value(char value = 0x2F);
+ void set_pulse_duration_value(char value = 0x2F);
+ void set_latency_time_value(char value =0x2F);
+ 
+ /*some auxillary functions that describes its status*/
+ signed char status();
+ 
+ 
+ 
+ };
+ #endif
\ No newline at end of file

diff -r 000000000000 -r 0d4a1401a9c5 main.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun Feb 05 21:03:49 2012 +0000
@@ -0,0 +1,15 @@
+#include "mbed.h"
+#include "MMA7455L_SPI.h"
+DigitalOut myled(LED1);
+Serial pc(USBTX, USBRX);
+MMA7455L_SPI acc(p5,p6,p7,p14);
+int main() {
+    while(1) {
+        acc.update_acceleration();
+        pc.printf("%f %5.3f %5.3f\r\n", acc.Ax, acc.Ay, acc.Az);
+        myled = 1;
+        wait(0.02);
+        myled = 0;
+        wait(0.02);
+    }
+}

diff -r 000000000000 -r 0d4a1401a9c5 mbed.bld
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Sun Feb 05 21:03:49 2012 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/b4b9f287a47e