Ashna Khemani

Waldo Worm

4 min read

MEAM 5100: Mechatronics (grad level)

Would you still look at my portfolio if I was a worm?

This class was a deep dive into things I previously took for granted (how does a motor keep a consistent speed, how do devices connect over wifi, how does a microcontroller work at the base level, etc). Basically my first look into embedded systems. It was really cool to dive under the hood and learn about the low-level hardware/circuitry and bit-level logic that tends to get abstracted away with platforms I’ve worked with in the past.

Snippet of code for this particular project is at the end.

Some other interesting projects from this class that I will probably add later include an IR remote and receiver, and my final project of a two-wheeled PID controlled robot controlled via wifi and based purely off this lower-level embedded code.

Code for Waldo Worm:

/* 
Project: MEAM 5100 Lab 3
Author: Ashna Khemani
Copyright (C) 2025 Ashna Khemani - All Rights Reserved
License: You may use, distribute and modify this code under the terms of the GNU GPLv3.0 license.
*/
 
 
#include "MEAM_general.h"  // includes the resources included in the MEAM_general.h file
#include "m_usb.h"
 
 
void initADC(int chan){
    /*
    chan: ADCchan port you wish to initialize
    */
 
    // set reference voltage to Vcc
    clear(ADMUX, REFS1); set(ADMUX, REFS0);
 
    // set ADC clock prescaling: 128
    set(ADCSRA, ADPS2); set(ADCSRA, ADPS1); set(ADCSRA, ADPS0);
 
    
 
    // disable digital input on desired port, and select as analog inp channel
    switch (chan){
        // ADC0, F0
        case 0: set(DIDR0,ADC0D); clear(ADCSRB,MUX5); clear(ADMUX,MUX2); clear(ADMUX,MUX1); clear(ADMUX,MUX0); 
            break;
        case 1: set(DIDR0,ADC1D); clear(ADCSRB,MUX5); clear(ADMUX,MUX2); clear(ADMUX,MUX1); set(ADMUX,MUX0); 
            break;
        case 4: set(DIDR0,ADC4D); clear(ADCSRB,MUX5); set(ADMUX,MUX2); clear(ADMUX,MUX1); clear(ADMUX,MUX0); 
            break;
        case 5: set(DIDR0,ADC5D); clear(ADCSRB,MUX5); set(ADMUX,MUX2); clear(ADMUX,MUX1); set(ADMUX,MUX0); 
            break;
        case 6: set(DIDR0,ADC6D); clear(ADCSRB,MUX5); set(ADMUX,MUX2); set(ADMUX,MUX1); clear(ADMUX,MUX0); 
            break;
        case 7: set(DIDR0,ADC7D); clear(ADCSRB,MUX5); set(ADMUX,MUX2); set(ADMUX,MUX1); set(ADMUX,MUX0); 
            break;
        case 8: set(DIDR2,ADC8D); set(ADCSRB,MUX5); clear(ADMUX,MUX2); clear(ADMUX,MUX1); clear(ADMUX,MUX0); 
            break;
        case 9: set(DIDR2,ADC9D); set(ADCSRB,MUX5); clear(ADMUX,MUX2); clear(ADMUX,MUX1); set(ADMUX,MUX0); 
            break;
        case 10: set(DIDR2,ADC10D); set(ADCSRB,MUX5); clear(ADMUX,MUX2); set(ADMUX,MUX1); clear(ADMUX,MUX0); 
            break;
        case 11: set(DIDR2,ADC11D); set(ADCSRB,MUX5); clear(ADMUX,MUX2); set(ADMUX,MUX1); set(ADMUX,MUX0); 
            break;
        case 12: set(DIDR2,ADC12D); set(ADCSRB,MUX5); set(ADMUX,MUX2); clear(ADMUX,MUX1); clear(ADMUX,MUX0); 
            break;
        case 13: set(DIDR2,ADC13D); set(ADCSRB,MUX5); set(ADMUX,MUX2); clear(ADMUX,MUX1); set(ADMUX,MUX0); 
            break;
    }
    set(ADCSRA, ADEN);
}
 
int readADC (int chan){
    /*
    chan: ADCchan to read from
    */
    initADC(chan);
 
    // ---- Dummy conversion ----
    set(ADCSRA, ADSC);
    while (!bit_is_set(ADCSRA, ADIF));
    set(ADCSRA, ADIF);
    (void)ADC;  // read and discard result
 
    set(ADCSRA, ADSC);  // enable adc; start conversion
    while(!bit_is_set(ADCSRA, ADIF));    // wait while conversion not done
    set(ADCSRA, ADIF);  // reset the flag
    int val = ADC;  // store the result
    return val;     // return value
 
}
 
int lin_interp (int x1, int x2, int y1, int y2, int x){
    return y1 + ((y2-y1) / (x2-x1)) * (x-x1);
}
 
int main(void)
{
    _clockdivide(0); //set the clock speed to 16Mhz
    m_usb_init();           // init printing
 
    // set motor output pins: DDR
    set(DDRB, 6); 
    set(DDRB, 7);
    set(DDRB, 5);
 
 
 
    // ------ Set Timer1 mode
    // Using timer1, set to mode14 for fastPWM which uses the ICR (the TOP value for counter)
    set(TCCR1B, WGM13); set(TCCR1B, WGM12); set(TCCR1A, WGM11); clear(TCCR1A, WGM10);
 
    // ------ Prescale Timer1 to 1/8 (want high-res)
    clear(TCCR1B, CS12); set(TCCR1B, CS11); clear(TCCR1B, CS10);
 
    // ------ Set ICR1 -- max or TOP value Timer1 can reach for mode14 pwm
    // f_des = f_timer / ICR --> 50 = 2MHz / ICR --> ICR = 40000
    ICR1 = 40000;
 
    // ------ Set COM (compare output mode)
    // what to do when timer matches compare reg/OCR: turn off ports
    // pins: PB6/OC1B/10 and PB7/OC1C/11
    set(TCCR1A, COM1B1); clear(TCCR1A, COM1B0);
    set(TCCR1A, COM1C1); clear(TCCR1A, COM1C0);
    set(TCCR1A, COM1A1); clear(TCCR1A, COM1A0);
 
 
 
    while (1){
        // Read and print out the pot values
        int leftPot = readADC(7);   // A0
        int rightPot = readADC(0);  // A5
        int headPot = readADC(1);   // A4
        
        // // Set the OCR values based on pot readings
        int pin11val = (int)lin_interp(675, 15, 1000, 5000, leftPot);   // "reversed"
        int pin10val = (int)lin_interp(120, 800, 1000, 5000, rightPot);
        int pin9val = (int)lin_interp(170, 900, 1000, 5000, headPot);
        // OCR1C = pin11val;    // 2000=5% of 40000 cycle=full CW. 4000=10% of 40000 cycle=full CCW
        // OCR1B = pin10val;
        // OCR1A = pin9val;
 
        m_usb_tx_uint(leftPot); m_usb_tx_string("\n"); //m_usb_tx_int(pin10val); m_usb_tx_string("\t");
        // m_usb_tx_int(rightPot); m_usb_tx_string("  "); m_usb_tx_int(pin11val); m_usb_tx_string("\n");
 
 
 
    }
    return 0;   /* never reached */
}

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