Diff: Encoder.cpp

Revision:

0:1d2644a20b71

Child:

1:2e39be3d2088

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Encoder.cpp	Mon Nov 24 03:33:29 2014 +0000
@@ -0,0 +1,110 @@
+#include "mbed.h"
+#include "Encoder.h"
+
+/***********************************************************
+Constructor
+***********************************************************/
+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)
+{
+    // When CSPin is high the device is unselected
+    _cs = 1;
+
+    //format SPI for 16 bit data, low steady state clock, second edge capture with 10MHz clock
+    _spi.format(16,1);
+    _spi.frequency(10000000);
+}
+
+/***********************************************************
+Parity Check Function
+***********************************************************/
+//Parity check.  Will be 0 if parity fails.  This is used for a safety check.
+
+bool Encoder::parity_calc(int x)
+{
+    x ^= x >> 8;
+    x ^= x >> 4;
+    x ^= x >> 2;
+    x ^= x >> 1;
+    x &= 1;
+    return x;
+}
+
+/***********************************************************
+Initialize Read_Encoder
+***********************************************************/
+//Taken from Init.cpp, used to be zero_ang_L, changed to zero_ang to accompany change to local variable
+//approximate point where the pilot should be standing straight
+
+void Encoder::init(float blah)
+{
+    zero_ang=blah;
+}
+
+/***********************************************************
+Read_Encoder Program
+***********************************************************/
+//Reads the encoder, does parity check, and stores the error flag.
+//@returns An unsigned integer which is the number of ticks away from the zero position.
+
+int Encoder::read()
+{
+    // Select the device by seting chip select low
+    _cs = 0;
+
+    //send a dummy byte to the MOSI to get a reading through the MISO
+    raw=_spi.write(0xFFFF);
+
+    // Set the select back to low to allow the encoder to chill
+    _cs=1;
+
+    // XNOR parity check
+    parity=~(parity_calc(raw) ^ (raw>>15));
+
+    // Mask and bit shift to look at encoder flag value
+    enc_flag=(raw & 0x4000)>>14;
+
+    raw&=0x3FFF;
+
+    return raw;
+}
+
+short int Encoder::readRaw(){
+    return raw;
+    }
+/***********************************************************
+Translate Function - Translates Ticks to Position
+***********************************************************/
+// Translates the left encoder value from encoder ticks into degrees from the pilot's zero.
+// @param ticks The number of encoder ticks from the encoder zero to the current position.
+// @returns A float which is the degrees away from the pilot's zero position.
+
+
+float Encoder::angle()
+{
+    // converts the result (encoder tick position) to degrees
+    float pos = -sign*read()*enc2deg+zero_ang;
+    return pos;
+}
+
+/***********************************************************
+Get parity from parityFlag
+***********************************************************/
+//Error Flag.  The encoder has a built in hardware error flag.  This is used for a safety check.
+
+bool Encoder::parityFlag()
+{
+    return parity;
+}
+
+/***********************************************************
+Get enc_flag from encFlag
+***********************************************************/
+bool Encoder::encFlag()
+{
+    return enc_flag;
+}
+
+void Encoder::flip()
+{
+    sign=-sign;
+    }
\ No newline at end of file