james hatch / Mbed 2 deprecated Encoder

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Dependencies:   mbed

Encoder.cpp@2:6f9c364ebe40, 2015-07-01 (annotated)

Committer:
jahatch
Date:
Wed Jul 01 02:35:56 2015 +0000
Revision:
2:6f9c364ebe40
Parent:
0:0a457148bccf 
dfzfd

Who changed what in which revision?

UserRevisionLine numberNew contents of line
jahatch 0:0a457148bccf 1 #include "mbed.h"
jahatch 0:0a457148bccf 2 #include "Encoder.h"
jahatch 0:0a457148bccf 3
jahatch 0:0a457148bccf 4 /***********************************************************
jahatch 0:0a457148bccf 5 Constructor
jahatch 0:0a457148bccf 6 ***********************************************************/
jahatch 0:0a457148bccf 7 Encoder::Encoder(PinName mosi, PinName miso, PinName sck, PinName ncs): _cs(ncs), _spi(mosi,miso,sck), enc2deg(360./(pow(2.,14.)-1)), zero_ang(1),sign(1)
jahatch 0:0a457148bccf 8 {
jahatch 0:0a457148bccf 9 // When CSPin is high the device is unselected
jahatch 0:0a457148bccf 10 _cs = 1;
jahatch 0:0a457148bccf 11
jahatch 0:0a457148bccf 12 //format SPI for 16 bit data, low steady state clock, second edge capture with 10MHz clock
jahatch 0:0a457148bccf 13 _spi.format(16,1);
jahatch 2:6f9c364ebe40 14 _spi.frequency(96000000);
jahatch 0:0a457148bccf 15 }
jahatch 0:0a457148bccf 16
jahatch 0:0a457148bccf 17 /***********************************************************
jahatch 0:0a457148bccf 18 Parity Check Function
jahatch 0:0a457148bccf 19 ***********************************************************/
jahatch 0:0a457148bccf 20 //Parity check. Will be 0 if parity fails. This is used for a safety check.
jahatch 0:0a457148bccf 21
jahatch 0:0a457148bccf 22 bool Encoder::parity_calc(int x)
jahatch 0:0a457148bccf 23 {
jahatch 0:0a457148bccf 24 x ^= x >> 8;
jahatch 0:0a457148bccf 25 x ^= x >> 4;
jahatch 0:0a457148bccf 26 x ^= x >> 2;
jahatch 0:0a457148bccf 27 x ^= x >> 1;
jahatch 0:0a457148bccf 28 x &= 1;
jahatch 0:0a457148bccf 29 return x;
jahatch 0:0a457148bccf 30 }
jahatch 0:0a457148bccf 31
jahatch 0:0a457148bccf 32 /***********************************************************
jahatch 0:0a457148bccf 33 Initialize Read_Encoder
jahatch 0:0a457148bccf 34 ***********************************************************/
jahatch 0:0a457148bccf 35 //Taken from Init.cpp, used to be zero_ang_L, changed to zero_ang to accompany change to local variable
jahatch 0:0a457148bccf 36 //approximate point where the pilot should be standing straight
jahatch 0:0a457148bccf 37
jahatch 0:0a457148bccf 38 void Encoder::init(float blah)
jahatch 0:0a457148bccf 39 {
jahatch 0:0a457148bccf 40 zero_ang=blah;
jahatch 0:0a457148bccf 41 }
jahatch 0:0a457148bccf 42
jahatch 0:0a457148bccf 43 /***********************************************************
jahatch 0:0a457148bccf 44 Read_Encoder Program
jahatch 0:0a457148bccf 45 ***********************************************************/
jahatch 0:0a457148bccf 46 //Reads the encoder, does parity check, and stores the error flag.
jahatch 0:0a457148bccf 47 //@returns An unsigned integer which is the number of ticks away from the zero position.
jahatch 0:0a457148bccf 48
jahatch 0:0a457148bccf 49 int Encoder::read()
jahatch 0:0a457148bccf 50 {
jahatch 0:0a457148bccf 51 // Select the device by seting chip select low
jahatch 0:0a457148bccf 52 _cs = 0;
jahatch 0:0a457148bccf 53
jahatch 0:0a457148bccf 54 //send a dummy byte to the MOSI to get a reading through the MISO
jahatch 0:0a457148bccf 55 raw=_spi.write(0xFFFF);
jahatch 0:0a457148bccf 56
jahatch 0:0a457148bccf 57 // Set the select back to low to allow the encoder to chill
jahatch 0:0a457148bccf 58 _cs=1;
jahatch 0:0a457148bccf 59
jahatch 0:0a457148bccf 60 // XNOR parity check
jahatch 0:0a457148bccf 61 parity=~(parity_calc(raw) ^ (raw>>15));
jahatch 0:0a457148bccf 62
jahatch 0:0a457148bccf 63 // Mask and bit shift to look at encoder flag value
jahatch 0:0a457148bccf 64 enc_flag=(raw & 0x4000)>>14;
jahatch 0:0a457148bccf 65
jahatch 0:0a457148bccf 66 raw&=0x3FFF;
jahatch 0:0a457148bccf 67
jahatch 0:0a457148bccf 68 return raw;
jahatch 0:0a457148bccf 69 }
jahatch 0:0a457148bccf 70
jahatch 0:0a457148bccf 71 short int Encoder::readRaw(){
jahatch 0:0a457148bccf 72 return raw;
jahatch 0:0a457148bccf 73 }
jahatch 0:0a457148bccf 74 /***********************************************************
jahatch 0:0a457148bccf 75 Translate Function - Translates Ticks to Position
jahatch 0:0a457148bccf 76 ***********************************************************/
jahatch 0:0a457148bccf 77 // Translates the left encoder value from encoder ticks into degrees from the pilot's zero.
jahatch 0:0a457148bccf 78 // @param ticks The number of encoder ticks from the encoder zero to the current position.
jahatch 0:0a457148bccf 79 // @returns A float which is the degrees away from the pilot's zero position.
jahatch 0:0a457148bccf 80
jahatch 0:0a457148bccf 81
jahatch 0:0a457148bccf 82 float Encoder::angle()
jahatch 0:0a457148bccf 83 {
jahatch 0:0a457148bccf 84 // converts the result (encoder tick position) to degrees
jahatch 0:0a457148bccf 85 float pos = -sign*read()*enc2deg+zero_ang;
jahatch 0:0a457148bccf 86 return pos;
jahatch 0:0a457148bccf 87 }
jahatch 0:0a457148bccf 88
jahatch 0:0a457148bccf 89 /***********************************************************
jahatch 0:0a457148bccf 90 Get parity from parityFlag
jahatch 0:0a457148bccf 91 ***********************************************************/
jahatch 0:0a457148bccf 92 //Error Flag. The encoder has a built in hardware error flag. This is used for a safety check.
jahatch 0:0a457148bccf 93
jahatch 0:0a457148bccf 94 bool Encoder::parityFlag()
jahatch 0:0a457148bccf 95 {
jahatch 0:0a457148bccf 96 return parity;
jahatch 0:0a457148bccf 97 }
jahatch 0:0a457148bccf 98
jahatch 0:0a457148bccf 99 /***********************************************************
jahatch 0:0a457148bccf 100 Get enc_flag from encFlag
jahatch 0:0a457148bccf 101 ***********************************************************/
jahatch 0:0a457148bccf 102 bool Encoder::encFlag()
jahatch 0:0a457148bccf 103 {
jahatch 0:0a457148bccf 104 return enc_flag;
jahatch 0:0a457148bccf 105 }
jahatch 0:0a457148bccf 106
jahatch 0:0a457148bccf 107 void Encoder::flip()
jahatch 0:0a457148bccf 108 {
jahatch 0:0a457148bccf 109 sign=-sign;
jahatch 0:0a457148bccf 110 }