File content as of revision 16:976a1d0ea897:

/// 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 "main.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?]

char show_ir_debug_info = 0;            // Set to 1 to display (via PC) the list of IR readings & visible robots every timestep

/// The locate beacon function samples the IR radiation from all 8 side sensors over a period of 1 second in [BEACON_PERIOD / 2.5] (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()
{
    int sample_period = (BEACON_PERIOD * 2) / 5;
    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 ();
        if(i%2 == 0){
            set_center_led(1, 0.5);
            set_leds(0xAA,0x55);
        }else{
            set_center_led(2, 0.5);
            set_leds(0x55,0xAA);
        }
        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+=sample_period;
        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 = (sample_period * mid_point) - sample_period - (sample_period / 4);
                //out("MS Offset:%d Midpoint:%f\n Current Time:%d\n",microseconds_offset,mid_point,beacon_timer.read_us());
                int cycle_period = (BEACON_PERIOD * 10);
                if(microseconds_offset < 0) microseconds_offset += cycle_period;
                //If we have missed the start of the beacon this cycle, wait until the next cycle
                while(beacon_timer.read_us()% (cycle_period) > microseconds_offset){};
                //Now wait until the start of the beacon pulse
                while(beacon_timer.read_us()% (cycle_period) < 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 %dms after first block not detected\n",(BEACON_PERIOD / 100));   
            }
        }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 > 6) 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);
    }
    if(beacon_found == 0){
        set_leds(0x00,0x00);
        set_center_led(1, 1);
        display.clear_display();
        display.set_position(0,0);
        display.write_string("BEACON NOT FOUND");   
    }
}

// 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(BEACON_PERIOD / 10);  
    ir_emitter_ticker.attach_us(emitter_ticker_block,BEACON_PERIOD);
    wait_us(((BEACON_PERIOD * 4) / 10)); //Wait for middle of pulse
    ir_sample_ticker.attach_us(sample_ticker_block,BEACON_PERIOD);
}


//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 && disable_ir_emitters == 0){
        IF_set_IR_emitter_output(0, 1);
        IF_set_IR_emitter_output(1, 1);
        ir_emitter_timeout.attach_us(emitter_timeout_block,(BEACON_PERIOD * 8)/10);
    }  
}

//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;
                    //Debug--
                    //out("Robot %d: [%d][%d][%d][%d][%d][%d][%d][%d]\n",test_robot,ir_sensor_data[i][0],ir_sensor_data[i][1],ir_sensor_data[i][2],ir_sensor_data[i][3],ir_sensor_data[i][4],ir_sensor_data[i][5],ir_sensor_data[i][6],ir_sensor_data[i][7]);
                    robots_heading[test_robot] = get_bearing_from_ir_array (ir_sensor_data[i]);
                    robots_distance[test_robot] = highest;
                }else robots_found[test_robot] = 0;   
            }  
         }
      }
      if(show_ir_debug_info == 1)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");
}

//Returns a 0 if turn is likely to complete in a single timestep, 1 if it is beyond range for single timestep and 2 if the beacon is not found so bearing unknown
char turn_to_bearing(int bearing)
{
    if(beacon_found == 0){
        out("Beacon not found: cannot turn to specific bearing");   
        return 2;
    }else{
        //First calculate the bearing using the angle of beacon relative to robot
        int current_bearing = 360 - beacon_heading;
        //Now work out turn needed to face intended heading
        int target_turn = (bearing - current_bearing) % 360;
        //Adjust to take 10% off turn, stops overshoot
        target_turn = (target_turn * 9) / 10;
        if(target_turn > 180) target_turn -= 360;
        if(target_turn < -180) target_turn += 360;
        //We can't reliably turn more than 280 degrees per second, so set a limit for the turn to that
        char beyond_limit = 0;
        int turn_limit = BEACON_PERIOD / 358;
        if(target_turn > turn_limit) {target_turn = turn_limit; beyond_limit = 1;};
        if(target_turn < -turn_limit) {target_turn = -turn_limit; beyond_limit = 1;};
        out("Turning %d degrees\n",target_turn);
        time_based_turn_degrees(1, target_turn,1);
        return beyond_limit;
    }
}