Diff: beacon.cpp

Revision:

6:ff3c66f7372b

Child:

7:ef9ab01b9e26

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/beacon.cpp	Thu Oct 22 00:46:14 2015 +0000
@@ -0,0 +1,333 @@
+/// PsiSwarm Beautiful Meme Project Source Code
+/// Version 0.1
+/// James Hilder, Alan Millard, Homero Elizondo, Jon Timmis
+/// University of York
+
+// Beacon.cpp - Functions for detecting the beacon and taking IR readings of the robots
+
+#include "psiswarm.h"
+
+int pulse_step = 1;                     //Pulse-step corresponds to which timeslot (0-9) is currently active, where beacon=0 and robots=2-8
+int low_threshold;                      //Set to be 2x mean background IR
+int beacon_threshold;                   //Set to be 4x mean background IR
+unsigned short ir_sensor_data[9][8];    // The raw sensor data from all 9x 50ms sample windows
+Ticker ir_sample_ticker;                // Ticker for the IR data sampling and processing; runs every 50ms in middle of timeslot
+Ticker ir_emitter_ticker;               // Ticker for turning on the IR emitters; runs every 50ms near start of timeslot
+Timeout ir_emitter_timeout;             // Timeout for turning off the IR emitters after 40ms
+Timer beacon_debug_timer;               // Timer for debug information only [remove later?]
+
+
+
+/// The locate beacon function samples the IR radiation from all 8 side sensors over a period of 1 second in 20ms blocks.
+/// The infrared beacon is set to give a 50ms burst of IR every 500ms.  We should thus see in the sampled radiation 2 blocks
+/// of samples, 2 or 3 samples in duration, when a significant peak occurs; the blocks should be 25 samples apart.
+void locate_beacon()
+{
+    out("1) Searching for IR beacon...");
+    unsigned short samples[50][9];
+    Timer beacon_timer;
+    beacon_timer.start();
+    int offset = 0;
+    //This loop samples the background IR values at 50Hz for 1 second and stores in an array
+    for(int i=0; i<50; i++) {
+        store_background_raw_ir_values ();
+        samples[i][8]=0;
+        for(int j=0; j<8; j++) {
+            samples[i][j] = get_background_raw_ir_value(j);
+            samples[i][8] += get_background_raw_ir_value(j);
+        }
+        offset+=20000;
+        while(beacon_timer.read_us() < offset) {}
+    }
+
+    //Print values: for testing [comment out]
+    /*
+    for(int i=0; i<50; i++) {
+        out("IR %d:",i);
+        for(int j=0; j<8; j++) {
+            out("[%d:%d]",j,samples[i][j]);
+        }
+        out("  [SUM:%d]\n",samples[i][8]);
+    }
+    */
+
+    //Bubble sort sums to find (6) highest values
+    unsigned short sorted_array[50];
+    for(int i=0; i<50; i++) {
+        sorted_array[i]=samples[i][8];
+    }
+    for (int c = 0 ; c < 49; c++) {
+        for (int d = 0 ; d < (50-c-1); d++) {
+            if (sorted_array[d] > sorted_array[d+1]) {
+                unsigned short swap = sorted_array[d];
+                sorted_array[d] = sorted_array[d+1];
+                sorted_array[d+1] = swap;
+            }
+        }
+    }
+
+    //Print sorted values: for testing [comment out]
+    /*
+    out("Sorted values:");
+    for (int c = 0 ; c < 50 ; c++ ) {
+        out("%d", sorted_array[c]);
+        if(c<49)out(",");
+    }
+    out("\n");
+    */
+
+    // Calculate mean background sum value by looking at 44 lowest sum values
+    int background_mean = 0;
+    for(int i=0;i<44;i++)background_mean += sorted_array[i];
+    background_mean /= 44;
+    
+    //out("Background mean value: %d\n",background_mean);
+    
+    //Our beacon threshold will be 4x the background mean value; find all instances where this occurs
+    low_threshold = background_mean * 2;
+    beacon_threshold = background_mean * 4;
+    char beacon_detected_indices[50];
+    for(int i=0;i<50;i++){
+        if(samples[i][8] > beacon_threshold) beacon_detected_indices[i]=1;
+        else beacon_detected_indices[i]=0;
+    }
+    //Count and display matches
+    int beacon_detected_count = 0;
+    char output_string[251] = "";
+    for(int i=0;i<50;i++){
+        if(beacon_detected_indices[i] == 1){
+            beacon_detected_count++;
+            char index_string[6];
+            sprintf(index_string,"[%d],",i);   
+            strcat(output_string,index_string);
+        }
+    }
+    //out("%d samples are above threshold:%s\n",beacon_detected_count,output_string);
+    
+    //We will use this array to store average values for each sensor when the beacon is detected
+    unsigned short beacon_averages[8];
+    char beacon_averages_count = 0;
+    for(int i=0;i<8;i++)beacon_averages[i]=0;
+    
+    //Now determine if the beacon is correctly found: must adhere to a set of rules
+    //Firstly, we should have not less than 4 and not more than 6 positive matches 
+    if(beacon_detected_count>3 && beacon_detected_count<7){
+        // Now verify that the positive samples are in valid places...
+        // Find first positive sample
+        int first_index = 0;
+        //out("Here\n",first_index);
+        
+        while(beacon_detected_indices[first_index]==0)first_index ++;
+        
+        //out("First index:%d\n",first_index);
+        
+        
+        // Check if first index is zero: if so, we need to check index 49 (and 48) to see if they are also high
+        if(first_index == 0){
+            if(beacon_detected_indices[49]>0)first_index = 49;
+            if(beacon_detected_indices[48]>0)first_index = 48;   
+        }
+        
+        beacon_averages_count++;
+        for(int i=0;i<8;i++){beacon_averages[i]+=samples[first_index][i];}
+        
+        // Now count the length of the 'block' of positive hits: must be equal to 2 or 3
+        char block_length = 1;
+        int end_index = first_index + 1;
+        if(end_index == 50) end_index = 0;
+        while(beacon_detected_indices[end_index]>0){
+            beacon_averages_count++;
+            for(int i=0;i<8;i++){beacon_averages[i]+=samples[end_index][i];}
+            block_length ++;
+            end_index ++;
+            if(end_index == 50) end_index = 0;   
+        }
+        if(block_length==2 || block_length == 3){
+            //We have found the first correct block and it is valid; now calculate its mid-point and check that the second block is also present 500ms later
+            float mid_point;
+            char second_block_okay = 0;
+            if(block_length == 2){
+                mid_point = first_index + 0.5;
+                char second_block_low = first_index + 25;
+                char second_block_high = first_index + 26;
+                if(second_block_low > 49) second_block_low -= 50;
+                if(second_block_high > 49) second_block_high -= 50;
+                beacon_averages_count+=2;
+                for(int i=0;i<8;i++){beacon_averages[i]+=samples[second_block_low][i]+samples[second_block_high][i];}
+                if(beacon_detected_indices[second_block_low]>0 && beacon_detected_indices[second_block_high]>0) second_block_okay = 1;
+            }
+            if(block_length == 3){
+                mid_point = first_index + 1;
+                if(mid_point == 50) mid_point = 0;
+                char second_block_single = first_index + 26;
+                if(second_block_single > 49) second_block_single -= 50;
+                beacon_averages_count++;
+                for(int i=0;i<8;i++){beacon_averages[i]+=samples[second_block_single][i];}
+                if(beacon_detected_indices[second_block_single]>0) second_block_okay = 1;
+            }   
+            if(second_block_okay >0){
+                beacon_found = 1;
+                beacon_heading = get_bearing_from_ir_array(beacon_averages);
+                out("Found at %d degrees\n",beacon_heading);
+                //for(int i=0;i<8;i++){
+                //    beacon_averages[i] /= beacon_averages_count;
+                //    out("[%d]",beacon_averages[i]);   
+                //}
+                out("2) Synchronising...\n");
+                // Calculate the offset to the expected start of the next beacon pulse
+                int microseconds_offset = (20000 * mid_point) - 25000;
+                //out("MS Offset:%d Midpoint:%f\n Current Time:%d\n",microseconds_offset,mid_point,beacon_timer.read_us());
+                if(microseconds_offset < 0) microseconds_offset += 500000;
+                //If we have missed the start of the beacon this cycle, wait until the next cycle
+                while(beacon_timer.read_us()%500000 > microseconds_offset){};
+                //Now wait until the start of the beacon pulse
+                while(beacon_timer.read_us()%500000 < microseconds_offset){};
+                /*
+                out("Now:%d",beacon_timer.read_us());
+                Timer test_timer;
+                test_timer.start();
+                for(int i=0;i<50;i++){
+                    store_background_raw_ir_values ();
+                    out("Time %d: %d\n",test_timer.read_ms(),get_background_raw_ir_value(2));
+                    while(test_timer.read_ms() % 10 < 9){};
+                }
+                */
+            }else{
+                beacon_found = 0;
+                out("Beacon not found: a matching second block 500ms after first block not detected\n");   
+            }
+        }else{
+            beacon_found = 0;
+            if(block_length == 1) out("Beacon not found: a single sample [%d] was high but not its neighbours\n",first_index);
+            if(block_length > 3) out("Beacon not found: a block of %d high samples was detected\n",block_length);   
+        }
+    } else {
+        beacon_found = 0;
+        if(beacon_detected_count > 7) out("Beacon not found: too many high samples [%d]\n",beacon_detected_count);
+        else out("Beacon not found: too few high samples [%d]\n",beacon_detected_count);
+    }
+    wait(1);
+}
+
+// The start_infrared_timers() function is called as soon as the beacon has been detected and synchronised to
+// It launches 2 tickers at offset times; the first is responsible for turning the robots IR emitters on in its proper timeslot
+// The other reads the values given from the IR sensor in the middle of each timeslot and processes that information in the final timeslot  
+void start_infrared_timers()
+{
+    // At this point we should be exactly at the start of a beacon cycle.
+    // We want the emitter ticker to start in approx 5ms (this will let us set a 40ms pulse)
+    // We want the sample ticker to start in approx 25ms (this will let us sample in the middle each step
+    out("3) Starting TDMA infrared timers\n");
+    beacon_debug_timer.start();
+    wait_us(4000);  //Adjusted down for PC message
+    ir_emitter_ticker.attach_us(emitter_ticker_block,50000);
+    wait_us(20000); //Wait for middle of pulse
+    ir_sample_ticker.attach_us(sample_ticker_block,50000);
+}
+
+
+//Return the max value in IR array
+unsigned short get_highest_sample(unsigned short * ir_array){
+    unsigned short highest = 0;
+    for(int i=0;i<8;i++){
+        if(ir_array[i]>highest) highest=ir_array[i];
+    }   
+    return highest;
+}
+
+//Return the sum total of IR array
+unsigned short get_sum_sample(unsigned short * ir_array){
+    unsigned short sum = 0;
+    for(int i=0;i<8;i++){
+        sum+=ir_array[i];
+    }   
+    return sum;  
+}
+
+//The emitter_ticker_block function runs every 50ms and turns the IR emitters on when pulse_step-1 matches the robot ID
+//It then starts a timeout to run emitter_timeout_block after 40ms, which turns off the emitters
+void emitter_ticker_block(){
+    //If the time-step (-1) equals my ID, turn on my emitters for 40ms
+    if(pulse_step-1 == robot_id){
+        IF_set_IR_emitter_output(0, 1);
+        IF_set_IR_emitter_output(1, 1);
+        ir_emitter_timeout.attach_us(emitter_timeout_block,40000);
+    }  
+}
+
+//Turn off the emitters
+void emitter_timeout_block(){
+     //Turn off IR emitters
+     IF_set_IR_emitter_output(0, 0);
+     IF_set_IR_emitter_output(1, 0);
+}
+
+//The function sample_ticker_block() is called every 50ms, and should run close to the middle of every timeslot
+//There are 10 time slots in each 500ms period
+//Slot 0 is when the beacon is flashing
+//Slot 1 should be IR-free and is used to measure background IR data, stored in background_sensor_data[]
+//Slot 2-8 are for the 7 robots; slot-1 = robot_id
+//In slot 9, the robot processes the data [and doesn't store and new readings]
+//It checks if the beacon is visible, if any robots are, calculates their bearings if they are, and transfers the background and active IR data for the robot
+void sample_ticker_block(){
+    //If we are in time-step 0 to 8, store the background data in an array
+    if(pulse_step < 9){
+    store_background_raw_ir_values ();
+    for(int i=0;i<8;i++)ir_sensor_data[pulse_step][i]=get_background_raw_ir_value(i);
+    }else{
+      //If not, process the data   
+      for(int i=0;i<9;i++){
+         unsigned short sum = get_sum_sample(ir_sensor_data[i]);
+         unsigned short highest = get_highest_sample(ir_sensor_data[i]);
+         //Check if beacon is visible
+         if(i==0){
+             if(sum > beacon_threshold){
+                 beacon_found = 1;
+                 beacon_heading = get_bearing_from_ir_array (ir_sensor_data[0]);
+             }else beacon_found = 0;
+             //out("Beacon sum:%d 0:%d 4:%d\n",sum,ir_sensor_data[0][0],ir_sensor_data[0][4]);
+         }
+         if(i==1){
+            for(int j=0;j<8;j++)background_sensor_data[j]=ir_sensor_data[1][j];   
+         }
+         if(i>1){
+            char test_robot = i-1;
+            if(test_robot == robot_id){
+                for(int j=0;j<8;j++)reflected_sensor_data[j]=ir_sensor_data[i][j];   
+            }else{
+                if(sum > low_threshold){
+                    robots_found[test_robot] = 1;
+                    robots_heading[test_robot] = get_bearing_from_ir_array (ir_sensor_data[i]);
+                    robots_distance[test_robot] = highest;
+                }else robots_found[test_robot] = 0;   
+            }  
+         }
+      }
+      display_ir_readings();
+    }
+    //Increment pulse step
+    pulse_step++;
+    if(pulse_step == 10) pulse_step = 0;
+}
+
+
+//Testing function to print out lines showing what robot can currently see in terms of beacon, other robots and obstacles
+void display_ir_readings()
+{
+    out("____________________________________\nInfrared Detection at %d ms\n",beacon_debug_timer.read_ms());
+    if(beacon_found==1){
+        out("Beacon detected at %d degrees\n",beacon_heading);
+    }  
+    for(int j=1;j<8;j++){
+        if(robots_found[j])out("Robot %d detected at %d degrees, %d distance\n",j,robots_heading[j],robots_distance[j]);       
+    }   
+    out("Reflected values:");
+    for(int i=0;i<8;i++){
+        out("[%d,%d]",i,reflected_sensor_data[i]);
+    }
+    out("\nBackground values:");
+    for(int i=0;i<8;i++){
+        out("[%d,%d]",i,background_sensor_data[i]);
+    }
+    out("\n\n");
+}
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