Microcontroller Board Testing

Group Assignment: Team Botswana-Lesotho

For this group assignment, we used the test equipment available in our lab to observe and analyze the operation of a microcontroller circuit board. Specifically, we demonstrated the use of a multimeter and an oscilloscope to measure and visualize electrical signals on the board. This process is essential for debugging, validating, and understanding the behavior of embedded systems.

Overview of Test Equipment

• Multimeter: Used to measure voltage, current, and resistance at various points on the circuit board.
• Oscilloscope: Used to visualize time-varying signals, such as digital pulses or analog waveforms, on the microcontroller pins.

Step-by-Step Process

1. Preparing the Microcontroller Board:
   • We selected a microcontroller development board (Arduino UNO) and ensured it was programmed with a simple firmware that toggles an LED and outputs a PWM signal.

                                       int led = 6;           // the PWM pin the LED is attached to
   int brightness = 0;    // how bright the LED is
   int fadeAmount = 1;    // how many points to fade the LED by
   
   void setup() {
     pinMode(led, OUTPUT); // declare pwm pin to be an output:
   }
   
   void loop() {
     analogWrite(led, brightness); // set the brightness of led
   
     // change the brightness for next time through the loop:
     brightness = brightness + fadeAmount;
   
     // reverse the direction of the fading at the ends of the fade:
     if (brightness <= 0 || brightness >= 255) {
       fadeAmount = -fadeAmount;
     }  
     delay(30);  // wait for 30 milliseconds to see the dimming effect
   }
                                   

   • The board was powered using a regulated 5V supply.
   

   Microcontroller board prepared for testing

2. Using the Multimeter:
   • We measured the supply voltage at the VCC and GND pins to confirm the board was receiving the correct voltage (5.00V).
   • We checked the continuity of the ground and power rails to ensure proper connections.
   • We measured the voltage at the LED pin to verify its toggling state (0V when off, ~5V when on).
   

   Measuring voltage and continuity with a multimeter

3. Using the Oscilloscope:
   • We connected the oscilloscope probe to the microcontroller's PWM output pin.
   • The oscilloscope displayed the PWM waveform, showing the frequency and duty cycle generated by the firmware.
   • We adjusted the time base and voltage scale to clearly observe the digital transitions and pulse width.
   • We also probed the LED pin to visualize the toggling signal as a square wave.
   

   Observing PWM signal on the oscilloscope

4. Documenting Observations:
   • We recorded the measured voltages, continuity checks, and oscilloscope screenshots.
   • We noted the PWM frequency (e.g., 490 Hz) and duty cycle (e.g., 50%) as observed on the oscilloscope.
   

   Captured PWM waveform on oscilloscope

Summary Table of Measurements

Conclusion

By using both the multimeter and oscilloscope, we were able to verify the correct operation of the microcontroller board. The multimeter confirmed proper supply voltage and signal toggling, while the oscilloscope allowed us to visualize and measure the timing characteristics of the PWM output. These tools are essential for diagnosing issues, validating designs, and gaining deeper insight into embedded electronic systems.