Bruno Allaire-Lemay / Mbed 2 deprecated APP1test

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Dependencies:   mbed

Fork of APP1 by Team APP

Accelerometer.cpp@6:3facf0329142, 2017-01-15 (annotated)

Committer:
dupm2216
Date:
Sun Jan 15 02:04:23 2017 +0000
Revision:
6:3facf0329142
Parent:
5:f59b51ac4b40
Child:
7:1e00dfecc92d
Move utility functions out of Accelerometer

Who changed what in which revision?

UserRevisionLine numberNew contents of line
dupm2216 1:7becb0e903e3 1 #include "Accelerometer.hpp"
dupm2216 6:3facf0329142 2 #include "Utility.hpp"
dupm2216 1:7becb0e903e3 3
dupm2216 3:1a9d0f0a50bf 4 //Compute inverse two's complement to obtain a signed value
dupm2216 3:1a9d0f0a50bf 5 //See page 21: https://www.gel.usherbrooke.ca/s5info/h17/doc/app1/file/MMA8452Q.pdf
dupm2216 3:1a9d0f0a50bf 6 //See: https://en.wikipedia.org/wiki/Two's_complement
dupm2216 3:1a9d0f0a50bf 7 //Turns out, the signed char does it for free
dupm2216 3:1a9d0f0a50bf 8 //We have to specify "signed char" because the "standard does not specify if plain char is signed or unsigned"
dupm2216 3:1a9d0f0a50bf 9 //http://stackoverflow.com/a/2054941/3212785
dupm2216 3:1a9d0f0a50bf 10 int raw_axis_data_to_int(signed char raw_axis_data)
dupm2216 3:1a9d0f0a50bf 11 {
dupm2216 3:1a9d0f0a50bf 12 return raw_axis_data;
dupm2216 3:1a9d0f0a50bf 13 }
dupm2216 3:1a9d0f0a50bf 14
dupm2216 3:1a9d0f0a50bf 15 char get_axis_register(Axis axis)
dupm2216 3:1a9d0f0a50bf 16 {
dupm2216 3:1a9d0f0a50bf 17 switch(axis)
dupm2216 3:1a9d0f0a50bf 18 {
dupm2216 3:1a9d0f0a50bf 19 case AXIS_X: return OUT_X_MSB_REGISTER;
dupm2216 3:1a9d0f0a50bf 20 case AXIS_Y: return OUT_Y_MSB_REGISTER;
dupm2216 3:1a9d0f0a50bf 21 case AXIS_Z: return OUT_Z_MSB_REGISTER;
dupm2216 3:1a9d0f0a50bf 22 default: return AXIS_INVALID;
dupm2216 3:1a9d0f0a50bf 23 }
dupm2216 3:1a9d0f0a50bf 24 }
dupm2216 5:f59b51ac4b40 25
dupm2216 5:f59b51ac4b40 26 double g_force_from_int_axis_data(const int axis_data)
dupm2216 5:f59b51ac4b40 27 {
dupm2216 5:f59b51ac4b40 28 return (double)axis_data / 64.0;
dupm2216 5:f59b51ac4b40 29 }
dupm2216 5:f59b51ac4b40 30
dupm2216 5:f59b51ac4b40 31 //Z axis is perpendicular to the horizontal plane, towards the floor when the accelerometer is flat
dupm2216 5:f59b51ac4b40 32 //Therefore,
dupm2216 5:f59b51ac4b40 33 // - if the Z force is +1g, the accelerometer is flat
dupm2216 5:f59b51ac4b40 34 // - if the Z force is -1g, the accelerometer is upside down
dupm2216 5:f59b51ac4b40 35 // - if the Z force is 0g, the accelerometer 90 degree from the horizontal
dupm2216 5:f59b51ac4b40 36 //sin(theta) = Z force in g
dupm2216 5:f59b51ac4b40 37 double angle_from_int_axis_data(const int axis_data)
dupm2216 5:f59b51ac4b40 38 {
dupm2216 5:f59b51ac4b40 39 const double z_g_force = g_force_from_int_axis_data(axis_data);
dupm2216 5:f59b51ac4b40 40 const double angle_radian = acos(fabs(z_g_force));
dupm2216 6:3facf0329142 41 return utility::degree_from_radian(angle_radian);
dupm2216 5:f59b51ac4b40 42 }
dupm2216 5:f59b51ac4b40 43
dupm2216 3:1a9d0f0a50bf 44 Accelerometer::Accelerometer(
dupm2216 3:1a9d0f0a50bf 45 PinName sda_pin,
dupm2216 3:1a9d0f0a50bf 46 PinName scl_pin,
dupm2216 3:1a9d0f0a50bf 47 const int slave_address
dupm2216 3:1a9d0f0a50bf 48 ) :
dupm2216 3:1a9d0f0a50bf 49 device(sda_pin, scl_pin),
dupm2216 1:7becb0e903e3 50 slave_address(slave_address)
dupm2216 1:7becb0e903e3 51 {
dupm2216 1:7becb0e903e3 52 }
dupm2216 1:7becb0e903e3 53
dupm2216 1:7becb0e903e3 54 void Accelerometer::write_register(const char register_address, const char new_value)
dupm2216 1:7becb0e903e3 55 {
dupm2216 1:7becb0e903e3 56 const int left_shifted_slave_address = slave_address << 1;
dupm2216 1:7becb0e903e3 57 char data[2];
dupm2216 1:7becb0e903e3 58 data[0] = register_address;
dupm2216 1:7becb0e903e3 59 data[1] = new_value;
dupm2216 1:7becb0e903e3 60
dupm2216 1:7becb0e903e3 61 const int write_return = device.write(left_shifted_slave_address, data, 2);
dupm2216 1:7becb0e903e3 62 if(write_return < 0)
dupm2216 1:7becb0e903e3 63 {
dupm2216 1:7becb0e903e3 64 printf("Write error: I2C error");
dupm2216 1:7becb0e903e3 65 }
dupm2216 1:7becb0e903e3 66 }
dupm2216 1:7becb0e903e3 67
dupm2216 1:7becb0e903e3 68 char Accelerometer::read_register(const char register_address)
dupm2216 1:7becb0e903e3 69 {
dupm2216 1:7becb0e903e3 70 char result;
dupm2216 1:7becb0e903e3 71 const int left_shifted_slave_address = slave_address << 1;
dupm2216 1:7becb0e903e3 72
dupm2216 1:7becb0e903e3 73 const int write_return = device.write(left_shifted_slave_address, &register_address, 1, true);
dupm2216 1:7becb0e903e3 74 if(write_return < 0)
dupm2216 1:7becb0e903e3 75 {
dupm2216 1:7becb0e903e3 76 printf("Write error: I2C error");
dupm2216 1:7becb0e903e3 77 }
dupm2216 1:7becb0e903e3 78
dupm2216 1:7becb0e903e3 79 const int read_return = device.read(left_shifted_slave_address, &result, 1);
dupm2216 1:7becb0e903e3 80 if(read_return != 0)
dupm2216 1:7becb0e903e3 81 {
dupm2216 1:7becb0e903e3 82 printf("Read error: I2C error (nack)");
dupm2216 1:7becb0e903e3 83 }
dupm2216 1:7becb0e903e3 84
dupm2216 1:7becb0e903e3 85 return result;
dupm2216 1:7becb0e903e3 86 }
dupm2216 1:7becb0e903e3 87
dupm2216 1:7becb0e903e3 88 //axis_data must be an array of 6 bytes
dupm2216 3:1a9d0f0a50bf 89 void Accelerometer::read_all_axis(signed char* axis_data)
dupm2216 1:7becb0e903e3 90 {
dupm2216 1:7becb0e903e3 91 for(int i = 0; i < NUMBER_OF_DATA_REGISTERS; ++i)
dupm2216 1:7becb0e903e3 92 {
dupm2216 1:7becb0e903e3 93 const char current_register = OUT_X_MSB_REGISTER + i;
dupm2216 1:7becb0e903e3 94 axis_data[i] = read_register(current_register);
dupm2216 1:7becb0e903e3 95 }
dupm2216 1:7becb0e903e3 96 }
dupm2216 1:7becb0e903e3 97
dupm2216 1:7becb0e903e3 98 void Accelerometer::print_all_axis_data()
dupm2216 1:7becb0e903e3 99 {
dupm2216 3:1a9d0f0a50bf 100 signed char axis_data[NUMBER_OF_DATA_REGISTERS];
dupm2216 1:7becb0e903e3 101 for(int i=0; i<NUMBER_OF_DATA_REGISTERS; i++)
dupm2216 1:7becb0e903e3 102 {
dupm2216 1:7becb0e903e3 103 axis_data[i] = 0;
dupm2216 1:7becb0e903e3 104 }
dupm2216 1:7becb0e903e3 105
dupm2216 1:7becb0e903e3 106 read_all_axis(axis_data);
dupm2216 1:7becb0e903e3 107
dupm2216 1:7becb0e903e3 108 printf("Register content: ");
dupm2216 1:7becb0e903e3 109 for(int i=0; i<NUMBER_OF_DATA_REGISTERS; i++)
dupm2216 1:7becb0e903e3 110 {
dupm2216 1:7becb0e903e3 111 const int current_data = (int)(axis_data[i]);
dupm2216 1:7becb0e903e3 112 printf("%d, ", current_data);
dupm2216 1:7becb0e903e3 113 }
dupm2216 1:7becb0e903e3 114 printf("\r\n");
dupm2216 1:7becb0e903e3 115 }
dupm2216 1:7becb0e903e3 116
dupm2216 1:7becb0e903e3 117 void Accelerometer::set_standby()
dupm2216 1:7becb0e903e3 118 {
dupm2216 1:7becb0e903e3 119 const char previous_ctrl_reg1 = read_register(CTRL_REG1_REGISTER_ADDRESS);
dupm2216 1:7becb0e903e3 120 const char new_ctrl_reg1_value = previous_ctrl_reg1 & ~(0x01);
dupm2216 1:7becb0e903e3 121 write_register(CTRL_REG1_REGISTER_ADDRESS, new_ctrl_reg1_value);
dupm2216 1:7becb0e903e3 122 }
dupm2216 1:7becb0e903e3 123
dupm2216 1:7becb0e903e3 124 void Accelerometer::set_active()
dupm2216 1:7becb0e903e3 125 {
dupm2216 1:7becb0e903e3 126 const char previous_ctrl_reg1 = read_register(CTRL_REG1_REGISTER_ADDRESS);
dupm2216 1:7becb0e903e3 127 const char new_ctrl_reg1_value = previous_ctrl_reg1 | 0x01;
dupm2216 1:7becb0e903e3 128 write_register(CTRL_REG1_REGISTER_ADDRESS, new_ctrl_reg1_value);
dupm2216 1:7becb0e903e3 129 }
dupm2216 1:7becb0e903e3 130
dupm2216 1:7becb0e903e3 131 void Accelerometer::init()
dupm2216 1:7becb0e903e3 132 {
dupm2216 1:7becb0e903e3 133 set_active();
dupm2216 3:1a9d0f0a50bf 134 }
dupm2216 3:1a9d0f0a50bf 135
dupm2216 3:1a9d0f0a50bf 136 int Accelerometer::read_axis_data_8_bits(Axis axis)
dupm2216 3:1a9d0f0a50bf 137 {
dupm2216 3:1a9d0f0a50bf 138 const char axis_register = get_axis_register(axis);
dupm2216 3:1a9d0f0a50bf 139 const char register_value = read_register(axis_register);
dupm2216 3:1a9d0f0a50bf 140 return raw_axis_data_to_int(register_value);
dupm2216 5:f59b51ac4b40 141 }
dupm2216 5:f59b51ac4b40 142
dupm2216 5:f59b51ac4b40 143 double Accelerometer::get_angle_from_horizontal()
dupm2216 5:f59b51ac4b40 144 {
dupm2216 5:f59b51ac4b40 145 const int z_axis_data = read_axis_data_8_bits(AXIS_Z);
dupm2216 5:f59b51ac4b40 146 return angle_from_int_axis_data(z_axis_data);
dupm2216 1:7becb0e903e3 147 }