as5048spi.cpp

00001 #include "as5048spi.h"
00002 
00003 
00004 As5048Spi::As5048Spi(PinName mosi, PinName miso, PinName sclk, int ndevices) :
00005     _nDevices(ndevices),
00006     _spi(mosi, miso, sclk)
00007 {
00008 
00009             //chip select à 1
00010 
00011     // AS5048 needs 16-bits for is commands
00012     // Mode = 1: 
00013     //  clock polarity = 0 --> clock pulse is high
00014     //  clock phase = 1 --> sample on falling edge of clock pulse
00015     _spi.format(16, 1);
00016     
00017     // Set clock frequency to 1 MHz (max is 10Mhz)
00018     _spi.frequency(1000000);
00019     
00020     _readBuffer = new int[ndevices];
00021 }
00022 
00023 As5048Spi::~As5048Spi()
00024 {
00025     delete [] _readBuffer;
00026 }
00027 
00028 int As5048Spi::degrees(int sensor_result)
00029 {
00030     return mask(sensor_result) * 36000 / 0x4000;
00031 }
00032 
00033 
00034 int As5048Spi::radian(int sensor_result)
00035 {
00036     return mask(sensor_result) * 62832 / 0x4000;
00037 }
00038 
00039 bool As5048Spi::error(int device)
00040 {
00041     if( device == -1 ) {
00042         for(int i = 0; i < _nDevices; ++i) {
00043             if( _readBuffer[i] & 0x4000 ) {
00044                 return true;
00045             }
00046         }
00047     } else if( device < _nDevices ) {
00048         return (_readBuffer[device] & 0x4000) == 0x4000;
00049     }
00050     return false; 
00051 }
00052 
00053 
00054 void As5048Spi::frequency(int hz) 
00055 {
00056     _spi.frequency(hz);
00057 }
00058 
00059 int As5048Spi::mask(int sensor_result)
00060 {
00061     return sensor_result & 0x3FFF; // return lowest 14-bits
00062 }
00063 
00064 
00065 void As5048Spi::mask(int* sensor_results, int n)
00066 {
00067     for(int i = 0; i < n; ++i) {
00068         sensor_results[i] &= 0x3FFF;
00069     }
00070 }
00071 
00072 
00073 bool As5048Spi::parity_check(int sensor_result)
00074 {
00075     // Use the LSb of result to keep track of parity (0 = even, 1 = odd)
00076     int result = sensor_result;
00077     
00078     for(int i = 1; i <= 15; ++i) {
00079         sensor_result >>= 1;
00080         result ^= sensor_result;
00081     }
00082     // Parity should be even
00083     return (result & 0x0001) == 0;
00084 }
00085 
00086 const int* As5048Spi::read(As5048Command command)
00087 {
00088     _read(command); // Send command to device(s)
00089     return _read(AS_CMD_NOP); // Read-out device(s)
00090 }
00091 
00092 const int*  As5048Spi::read_sequential(As5048Command command)
00093 {
00094     return _read(command);
00095 }
00096 
00097 const int*  As5048Spi::read_angle()
00098 {  
00099     _read(AS_CMD_ANGLE); // Send command to device(s)
00100     return _read(AS_CMD_NOP); // Read-out device(s)
00101 }
00102 
00103 const int*  As5048Spi::read_angle_sequential()
00104 {
00105     return _read(AS_CMD_ANGLE); 
00106 }
00107 
00108 
00109 int* As5048Spi::_read(As5048Command command)
00110 {
00111     if(_nDevices == 1)
00112     {
00113         // Give command to start reading the angle
00114         //chip select à 0
00115 
00116         wait_us(1); // Wait at least 350ns after chip select
00117         _readBuffer[0] = _spi.write(command);
00118         //chip select à 1
00119 
00120         wait_us(1); // Wait at least 350ns after chip select       
00121     } else
00122     {
00123         // Enable the sensor on the chain
00124         //chip select à 0
00125 
00126          wait_us(1); // Wait at least 350ns after chip select
00127         for(int i = 0; i < _nDevices; ++i)
00128         {
00129             _readBuffer[i] = _spi.write(command);
00130         }
00131         //chip select a 1
00132         
00133         wait_us(1); // Wait at least 350ns after chip select
00134     }
00135     return _readBuffer;
00136 }
00137 
00138 
00139 
00140 
00141 
00142