Revision 0:2038ff2b7de5, committed 2016-06-25

Comitter:

electromotivated

Date:

Sat Jun 25 03:19:45 2016 +0000

Child:

1:a1207d543967

Commit message:

Fibonacci Linear Feedback Shift Register Pseudo-Random Number Generator; ;

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/FibonacciLFSR.cpp	Sat Jun 25 03:19:45 2016 +0000
@@ -0,0 +1,31 @@
+#include "FibonacciLFSR.h"
+#include "mbed.h"
+
+FibonacciLFSR::FibonacciLFSR(LFSR_SIZE_t size){
+    this->size = size;
+    this->lfsr_period = (1 << size) - 1;    // Number of random numbers
+    this->lfsr = 0x0001;
+}
+
+uint16_t FibonacciLFSR::getRandom(){
+    switch (size){
+        case LFSR_2:
+            feedback_bit = ((lfsr >> 1) ^ (lfsr >> 0)) & 0x01;
+            break;
+        case LFSR_4:
+            feedback_bit = ((lfsr >> 3) ^ (lfsr >> 2)) & 0x01;
+            break;
+        case LFSR_8:
+            feedback_bit = ((lfsr >> 7) ^ (lfsr >> 5) ^ (lfsr >> 4) ^ (lfsr >> 3)) & 0x01;
+            break;
+        case LFSR_16:
+            feedback_bit = ((lfsr >> 15) ^ (lfsr >> 14) ^ (lfsr >> 12) ^ (lfsr >> 3)) & 0x01;
+            break;
+        default: 
+            break;
+    }
+    
+    // Shift, add feedback, AND zero extra MSb's leaving only "size" number of bits representing lfsr
+    lfsr = ((lfsr << 1) | feedback_bit) & ((1 << size) - 1); 
+    return lfsr;
+}
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/FibonacciLFSR.h	Sat Jun 25 03:19:45 2016 +0000
@@ -0,0 +1,46 @@
+#ifndef FIBONACCI_LFSR
+#define FIBONACCI_LFSR
+
+/*
+    Library for Fibonacci Linear Feedback Shift Register pseudo-random number
+    generator. The uniqueness of the Fibonacci LFSR is that all permutations
+    (values) are explored except zero, ensuring at least one bit in the LFSR
+    is always HIGH. 
+    
+    Applications: Random Number Generation, LED Faux Candles, LED lighting 
+    effects, etc. 
+    
+    References: (Press "Ctrl" and click link to open in browser)
+    https://en.wikipedia.org/wiki/Linear-feedback_shift_register
+    
+    TODO: Consider making this class static
+*/
+
+#include "mbed.h"
+
+class FibonacciLFSR{
+    public:
+        typedef enum SIZE{
+            LFSR_2 = 2, LFSR_4 = 4, 
+            LFSR_8 = 8, LFSR_16 = 16
+        }LFSR_SIZE_t;
+        /*
+            Constructor of Fibonacci Linear Feedback Shift Register Objects.
+            Preconditions: None
+            @param size     Number of bits for LFSR 
+        */   
+        FibonacciLFSR(LFSR_SIZE_t size);
+        
+        /*
+            Generate and return new random number
+            @return    A new random value
+        */
+        uint16_t getRandom();
+        
+    private:
+        LFSR_SIZE_t size;              // The number of bits representing the LFSR
+        int lfsr_period;               // Period of LFSR register (number of random values before repeating)
+        uint16_t lfsr;              
+        uint16_t feedback_bit;      
+};
+#endif
\ No newline at end of file