Nipkow Disk 32 Line Television

1inary file (no preview

1inary file (no preview

1inary file (no preview

1inary file (no preview

1#include <avr/io.h>
2#include <avr/interrupt.h>
3#include "Arduino.h"
4#include  <SPI.h>
5#include <SD.h>
6
7// each frame contains 32x64 pixels ( 2048)
8//  each pixel is represented as one byte in a file on the SDcard. Only the lower 6  bits are used.
9// running at 16 frames/s about 32K bytes/s has to be read from  the SDcard.
10// the SD card can easily do that on average, but some reads take  much long than average.
11// To overcome this problem two 256 byte buffers are  used. When the device is streaming bytes from one buffer the other is being filled  from SD card.
12
13#define PinPulse               8  //  IR receiver circuit.  (must be connected to  input capture pin 8 )
14#define DAC_0LSB               2
15#define  DAC_1                  3 
16#define DAC_2                  4
17#define DAC_3                  5
18#define  DAC_4                  6
19#define DAC_5                  7
20
21#define SyncPixel              1005 // pixel number that should correspond with synchronisation pulse.  Tune this to so that pixel0 corresponds with the upper left corner.
22const byte  NumberOfPixelBits   = 11;    //  2^NumberOfPixelBits pixels
23
24// global variables  used in interrupt routines
25volatile unsigned int Pixel = 0x0700;    // current  pixel index                  
26volatile unsigned int lastT1capture, Period_Ticks;  // used to calculate spinning frequency
27volatile unsigned long NextOutputCompare32bit  = 0;
28volatile unsigned long PixelTime_16bitTickFraction = 1000000000;
29
30volatile  char SyncLow=0, SyncHigh =0;                                                                                                                                                                                     
31File  myFile;
32uint8_t buffer[512];
33int SubFrame = 0;
34long Frame = 0;
35
36
37void  setup()
38{
39  pinMode(DAC_0LSB, OUTPUT);  
40  pinMode(DAC_1, OUTPUT);    
41  pinMode(DAC_2, OUTPUT);
42  pinMode(DAC_3, OUTPUT);
43  pinMode(DAC_4, OUTPUT);
44  pinMode(DAC_5, OUTPUT);      
45  pinMode(PinPulse, INPUT);  // Configure input  capture pin on timer1
46  digitalWrite(PinPulse,0);  // floating may have 50 Hz  noise on it.
47  if (!SD.begin(10)) {
48     return;
49  }
50  myFile = SD.open("mov_26.bin");
51  cli();                    //clear interrupts while configuring timer1
52  TCCR1A  = 0;               //TC1 Control Register A 
53  TCCR1B = B01000011;       //TC1  Control Register B : free running 250kHz counter, noise canceller enabled, falling  edge input capture
54  TIMSK1 = B00100010;       //Timer/Counter 1 Interrupt Mask  Register: Enable input capture Interupt (ICIE) , Enable Output Compare A Match Interrupt  Enable (OCIEA)
55  sei();                    // enable interrupts
56}
57
58//  timer 1 capture interrupt: function is triggered each time the synchronisation hole  passes the light sensor.
59ISR (TIMER1_CAPT_vect)
60{ 
61  unsigned int T1capture  = ICR1 ;                    // read timer1 value when the sync occured
62  Period_Ticks  =  T1capture - lastT1capture;  // period = time between new and previous sync
63  if (Period_Ticks > 1000)                    // ignore very short periods
64  {
65    sei();                              // Increase max pixel clk by enabling nested  interrupts (allows COMPA interrupt during sync interrupt)
66    lastT1capture =  T1capture ;
67    signed int SyncError = Pixel - SyncPixel;      // We expect a  certain pixel number when sync occurs. Calculate error.
68    cli();                              //  atomic update of outputcompareStep32bit
69                                        //  Calculate time between pixels = (time between syncs)/NumberOfPixels + correct part  of the error. 
70                                        // Expressed as 32bit  value : 16 bit integer, 16bit fraction -> OutputCompareStep32bit
71    PixelTime_16bitTickFraction  = ( ( long)Period_Ticks << (16 - NumberOfPixelBits) ) + ((signed long)SyncError  << 6); // each sync a fraction of the error is corrected : 
72  } 
73}
74
75//  timer 1 output compare A interrupt :function is triggered each time a new pixel  should be send to the led
76ISR(TIMER1_COMPA_vect)
77{ 
78  PORTD = (PORTD &  0x03) | (((buffer[Pixel & 0x01FF]) & 0x3F)<<2); //  write 6 lower buffer values  to 6 bit DAC outputs on port D
79  OCR1A = (NextOutputCompare32bit >> 16);                          //  set new output compare value ( = integer part of OutputCompareStep32bit )
80  NextOutputCompare32bit  += (PixelTime_16bitTickFraction);         // calculate new output compare value
81   if ((Pixel & 0x01FF)==0x00) SyncHigh=1;                          //  trigger  to load high bank from SDcard to buffer ( currently reading from low bank )
82  if ((Pixel & 0x01FF)==0x0100) SyncLow=1;                         // trigger to  load low bank from SDcard to buffer ( currently reading from high bank )
83  Pixel++;                                                         // next pixel
84  if (Pixel  > ((1 << NumberOfPixelBits) - 1)) { Pixel = 0; } 
85}
86
87
88void loop() {
89if  (SyncLow)  { SyncLow=0;  myFile.read(buffer, 256); SubFrame++; }
90if (SyncHigh)  { SyncHigh=0; myFile.read(buffer+256, 256); SubFrame++;}
91if (!myFile.available())  Frame=0;
92if (SubFrame>7) { SubFrame=0; myFile.seek(2048*Frame); Frame++;}
93}       
94
95
96