Diff: ledScreen.h

Revision:

0:8b26631e8c70

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ledScreen.h	Tue Mar 06 19:58:34 2012 +0000
@@ -0,0 +1,238 @@
+#include "mbed.h"
+
+/*
+    TODO: wasrunning - works as intended?
+    TODO: OPTIME - tweak value
+
+*/
+
+extern "C" void frameout(unsigned char dsVal[], unsigned char transformedSource[]);
+
+class ledScreen {
+public:
+    ledScreen();
+    ~ledScreen() {}
+
+    void transformFrame(unsigned char* imageSource);
+    void outputFrame();
+    void start();   // start outputting frames on an interrupt
+
+private:
+
+    int MAX_PULSE_WIDTH; // constant: max enable pulse duration
+    int pulseLength; // length of current pulse (used in delta-sigma pwm)
+    int OP_TIME;
+
+    static const int XPANS = 3; // number of panels horizontally
+    static const int YUNITS = 1;
+    static const int YPANS = 3; // 3* YUNITS
+    static const int PIXPERPAN = 256;
+
+    int running;
+    int subFrameCtr;
+
+    Timeout nextFrameTimer; // timeout routine
+
+    // Buffers to hold the RGB data after rearranging to match the LED shifting pattern
+    unsigned char transformedSource[3*PIXPERPAN*XPANS*YPANS];
+
+    // Error values for all 256 brightness levels
+    unsigned int dsErr[256];
+    unsigned int ssdsErr[256];
+
+    // On/off state per sub-frame for all 256 brightness levels
+    unsigned char dsVal[256];
+
+    // Precomputed gamma for all 256 brightness levels
+    unsigned short gamma[256];
+
+
+    DigitalOut flatch; // data latch (for all connected panels in parallel)
+    DigitalOut MA0; // module address 0
+    DigitalOut MA1;
+    DigitalOut NREN; // active low enable for red channel (low -> LED on). Note: need to have enable high when latching data
+    DigitalOut Rdat0; // red data
+    DigitalOut Gdat0; // green data
+    DigitalOut Bdat0; // blue data
+    DigitalOut Rdat1; // red data
+    DigitalOut Gdat1; // green data
+    DigitalOut Bdat1; // blue data
+    DigitalOut Rdat2; // red data
+    DigitalOut Gdat2; // green data
+    DigitalOut Bdat2; // blue data
+    DigitalOut sclk; // clock
+    
+    DigitalOut debug;
+
+};
+
+ledScreen::ledScreen() :
+        flatch(p10), // data latch (for all connected panels in parallel)
+        MA0(p18), // module address 0
+        MA1(p19),
+        NREN(p9), // active low enable for red channel (low -> LED on). Note: need to have enable high when latching data
+        Rdat0(p15), // red data
+        Gdat0(p16), // green data
+        Bdat0(p17), // blue data
+        Rdat1(p7), // red data
+        Gdat1(p6), // green data
+        Bdat1(p5), // blue data
+        Rdat2(p13), // red data
+        Gdat2(p12), // green data
+        Bdat2(p11), // blue data
+        sclk(p14),
+        debug(p27) { // clock
+
+    // precompute gamma for every possible RGB intensity value (0-255).
+    // Gamma correction with gamma = 3, downshifting by 8 to bring the range of values back to 0-65535
+    for (int i=0; i<256; i++) {
+        gamma[i] = pow(i, 2.2) * 0.33;//(i*i*i)>>8;
+    }
+
+    // initialising lines
+    flatch = 1;
+    NREN = 1;
+    sclk = 1;
+
+    // initialising values
+    MAX_PULSE_WIDTH = 512; //must currently be a power of 2, and when changing this, you must change the ssdsErr crossover masking
+    pulseLength = MAX_PULSE_WIDTH;
+    OP_TIME = 510; //Determined by scoping. Change this every time you change num screens
+    //NUM_PANELS = 3
+
+    running=0;
+    subFrameCtr=0;
+
+    // initialising errors for delta-sigma
+    for (int j=0; j<256; j++) {
+        dsErr[j] = 0;
+        ssdsErr[j] = 0;
+    }
+
+}
+
+void ledScreen::start() {
+    running=1;
+    outputFrame();
+}
+
+
+
+void ledScreen::transformFrame(unsigned char* imageSource)
+{
+    int i=0;
+    int panseqnum=0, t=0, out=0, x=0, y=0, MA=0;
+
+    for (int q=0; q < 256*3*3*3; q+=3)
+    {
+        i = q/3;
+        
+        x = i % (16*XPANS);
+        y = i / (16*XPANS);
+        
+        
+        int MA = (y/16) % 3;
+        panseqnum = x/16 + y/(16*3) * XPANS;
+       
+        if (y%2 == 0)
+        {
+                t = (y%16)/2*0x20 + ((x%16)/8*0x10+(7-(x%16)%8));
+        }
+        else
+        {
+                t = 8 + (y%16)/2*0x20 + ((x%16)/8*0x10+(x%16)%8);
+        }
+       
+        out = 3*(MA * YUNITS * XPANS * 256 + t * XPANS * YUNITS + panseqnum);
+        
+        transformedSource[out] = imageSource[q];
+        transformedSource[out+1] = imageSource[q+1];
+        transformedSource[out+2] = imageSource[q+2];
+    }
+
+}
+
+// Output one frame and call itself after a period of time if running is set to true
+void ledScreen::outputFrame() {
+
+    debug = 1;
+
+    if (pulseLength != MAX_PULSE_WIDTH)
+        NREN = 0; // turn off
+
+    if (subFrameCtr<=0) subFrameCtr=36;
+    subFrameCtr--;
+
+    if (subFrameCtr == 0) {                  // Every cycle of delta sigma we take a snapshot of the error that needs to be corrected by the short pulses.
+        for (int i = 0; i < 256; i++) {      // This is required to eliminate visible flicker due to beat frequencies otherwise created.
+            dsErr[i] += ssdsErr[i] & 0xFE000000;
+            ssdsErr[i] %= 0x10000;
+            ssdsErr[i] += dsErr[i] % (512 * 0x10000);
+            dsErr[i] &= 0xFE000000;
+        }
+
+        // Doing delta sigma for the snapshot
+        for (int i = 0; i <= 9; i++) {
+            int lpl = 1<<i;
+
+            if (ssdsErr[i]/0x10000 & lpl)
+                ssdsErr[i]-=(0x10000-gamma[i])*lpl;
+            else
+                ssdsErr[i]+=gamma[i]*lpl;
+        }
+
+    }
+
+    // produce pulse lengths of 1, 2, 4, ... 256, spread throughout all subframes (only one in four are not MAX_PULSE_WIDTH long)
+    pulseLength = ((subFrameCtr%4)?MAX_PULSE_WIDTH:(1<<(subFrameCtr>>2)));
+
+    for (int i = 0; i < 256; i++) {
+        if (pulseLength == MAX_PULSE_WIDTH) {
+            // Delta-Sigma modulation with variable pulse length weighting
+            // Based on energy dimensions (time * amplitude)
+            if (dsErr[i] > (0x10000-gamma[i])*pulseLength) {
+                dsVal[i] = 0;//-1; Invert as we are using inverting buffers
+                dsErr[i]-=(0x10000-gamma[i])*pulseLength;
+            } else {
+                dsVal[i] = (unsigned char)-1;
+                dsErr[i]+=gamma[i]*pulseLength;
+            }
+        } else { // if short pulse
+            if (ssdsErr[i]/0x10000 & pulseLength) {
+                //Doing proper least significant delta sigma live still causes flicker (but only for dim pixels)
+                //ssdsErr[i]-=(0x10000-gamma[i])*pulseLength;
+                dsVal[i] = 0;
+            } else {
+                dsVal[i] = (unsigned char)-1;
+            }
+
+        }
+    }
+
+    // output data
+    for (int i = 0; i < 3; i++) { //FIX
+        MA0 = !(i&1);
+        MA1 = !(i&2);
+
+        frameout(dsVal, &transformedSource[i*256*3*3]);
+    }
+
+    NREN = 0; // need to have enables high before every latch, (in case we are on a long pulse)
+    flatch = 0; // latching all data to LEDs
+    flatch = 1;
+    NREN = 1; // turn on LEDs
+
+    if (pulseLength < 4) { // short pulses done through wait
+        wait_us(pulseLength);
+        NREN = 0; //Turn off LEDs
+
+        bool wasrunning = running;
+        running = false;
+        outputFrame(); //this will recurse only once due to the distrubution of pulses. pulseLength of the next instance will be attached.
+        running = wasrunning;
+    }
+    // long waits done through attaching an interrupt that will turn off the LEDs at the start of next function call.
+    // Meanwhile, the main code can run between the interrupts.
+    if (running) nextFrameTimer.attach_us(this, &ledScreen::outputFrame, (pulseLength == MAX_PULSE_WIDTH) ? pulseLength - OP_TIME : pulseLength);
+    debug = 0;
+}