Diff: Accelerometer.cpp

Revision:

3:1a9d0f0a50bf

Parent:

1:7becb0e903e3

Child:

4:303fb83498fd

--- a/Accelerometer.cpp	Sat Jan 14 18:53:39 2017 +0000
+++ b/Accelerometer.cpp	Sat Jan 14 22:37:34 2017 +0000
@@ -1,10 +1,35 @@
 #include "Accelerometer.hpp"
 
-Accelerometer::Accelerometer(I2C& device, const int slave_address) :
-    device(device),
+//Compute inverse two's complement to obtain a signed value
+//See page 21: https://www.gel.usherbrooke.ca/s5info/h17/doc/app1/file/MMA8452Q.pdf
+//See: https://en.wikipedia.org/wiki/Two's_complement
+//Turns out, the signed char does it for free
+//We have to specify "signed char" because the "standard does not specify if plain char is signed or unsigned"
+//http://stackoverflow.com/a/2054941/3212785
+int raw_axis_data_to_int(signed char raw_axis_data)
+{
+    return raw_axis_data;
+}
+
+char get_axis_register(Axis axis)
+{
+    switch(axis)
+    {
+        case AXIS_X: return OUT_X_MSB_REGISTER;
+        case AXIS_Y: return OUT_Y_MSB_REGISTER;
+        case AXIS_Z: return OUT_Z_MSB_REGISTER;
+        default: return AXIS_INVALID;
+    }
+}
+
+Accelerometer::Accelerometer(
+    PinName sda_pin, 
+    PinName scl_pin, 
+    const int slave_address
+    ) :
+    device(sda_pin, scl_pin),
     slave_address(slave_address)
 {
-    
 }
 
 void Accelerometer::write_register(const char register_address, const char new_value)
@@ -42,7 +67,7 @@
 }
 
 //axis_data must be an array of 6 bytes
-void Accelerometer::read_all_axis(char* axis_data)
+void Accelerometer::read_all_axis(signed char* axis_data)
 {
     for(int i = 0; i < NUMBER_OF_DATA_REGISTERS; ++i)
     {
@@ -53,7 +78,7 @@
 
 void Accelerometer::print_all_axis_data()
 {
-    char axis_data[NUMBER_OF_DATA_REGISTERS];
+    signed char axis_data[NUMBER_OF_DATA_REGISTERS];
     for(int i=0; i<NUMBER_OF_DATA_REGISTERS; i++)
     {
         axis_data[i] = 0;
@@ -87,4 +112,11 @@
 void Accelerometer::init()
 {
     set_active();
+}
+
+int Accelerometer::read_axis_data_8_bits(Axis axis)
+{
+    const char axis_register = get_axis_register(axis);
+    const char register_value = read_register(axis_register);
+    return raw_axis_data_to_int(register_value);
 }
\ No newline at end of file