7. Electronics design

Browse through the NuEval Handbook to review the evaluation criteria.

Group Assignment

Use the test equipment in your lab to observe the operation of a microcontroller circuit board

Multimeter

Logic Analyzer

Anna

Albert

I used testing equipment to examine a microprocessor.

The multimeter certainly earns its name, as it is capable of measure many different properties associated with electronics. The meter can be used with both A/C and D/C current. In our electronics settting, we are relying upon D/C current. The multimeter can measure voltage, resitance, current, and more. Additionally, the multimeter in the lab can produce small amounts of current to test components, for example testing an LED. As LEDs have a polarity, a multimeter might help test that the LED is in the correct orientation.

With my RP2040 board connected to USB (consequently, power), I used the multimeter to test several of the pins on the microprocessor. In the photo, I am connecting the 3.3V pin with the ground pin. The multimeter gives a reading of 3.3V, as expected. On the multimeter, the black wire is connected as ground, while using the red to probe.

It was a little awkward with the small chip to hold two probes and touch a pin. It would be better to use a clamp to hold the chip while doing this.

Reading voltage from connected microprocessor

I also tried examining electrical signals with an oscilloscope. An oscilloscope is a test instrument that displays varying voltages of signals as a function of time. I tried hooking up the power microprocessor, which was running code, to the oscilloscope. While I can see signal it was not well tuned to fully interpret the output. Further work (and instruction) is needed to fully harness the power of an oscilloscope. This is wth ith a running program (blinking an LED, as seen in my embedded programming group work).

Periodic signal seen on oscilloscope

With the small microprocessor, it was tricky to probe the microprocessor. There was a small hook on the probe which could be attached to a pin hole on the chip.

Probe from oscilloscope and microprocessor

In my oscilliscope work, I didn’t tune the instrument properly to see the expected square wave. Another key instrument in analyzing electronics is a logic analyzer. For this, I took a board which had an LED connected to the first pin (pin 0 in code) and wrote code to make it blink on one second intervals. I then connected this pin to a logic analyzer, and observed the output via the logic analyzer.

The Logic Analyzer used was an inexpensive HiLetGo USB Logic Analyzer. For software, I was able to connect this to Logic 2 from Saleae.

Blinking LED seen with square wave on Logic Analyzer

The code used to blink the LED.

// Pin assignments
const int led1 = D0;  // LED1 on pin 0

// Timing intervals (in milliseconds)
const unsigned long interval1 = 1000;

// Last toggle times
unsigned long previousMillis1 = 0;

// LED states
bool ledState1 = LOW;

void setup() {
  pinMode(led1, OUTPUT);
}

// loop turning LED off and on
void loop() {
  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis1 >= interval1) {
    previousMillis1 = currentMillis;
    ledState1 = !ledState1;
    digitalWrite(led1, ledState1);
  }
}

So far I have only slightly tapped the power of instruments to assist electronics work, and further work is needed to fully appreciate their benefit. I have already seen some benefit, and now know that these are power tools available to utilize in electronics work.

Evert

What Is a Multimeter?

A multimeter is an electronic tool used to measure voltage (V), current (A), and resistance (Ω). It can be digital or analog, but digital ones are more common and easier to read.

How to Use a Multimeter

When useing a multimeter then the first thing you need to analyse is what are you going to measure, when you know what you ar going to do you can start setting upp the meter for the measure ment you are going to do. I am going to do capasitor measure ment and find out how big capasitor i have in my hands. I am aslo going to do Voltages measurment.

Here is a picture of a multimeter that can do various measurment.

Now i am going to make capasitor measurment and find out how big this capasitor)see picture below) is in farad

To measure the capasitor the first thing we need to do is adjust the settings of the meter, on the picture below we can see how the settings are supposed to be.

Then it´s time to do the measurment, we take the red and the black probe and put them on each side of the capasitor and then we get the value of the capasitor. it is demonstratet in the video below how it´s done.

video code

In this video we can see that the capasitor is 950nF that egals to 1µF

how to measure voltage

We set the meter on DC voltage setting then we take the red probe and put it on the pluse side of the circut and the black probe on ther negative side of the circut.

Magnus

Oscilloscope PWM Sine Wave. Magnus

As an experiment on the oscilloscope we made a Simple Program using CHATGPT to get a PWM sine-wave. The schematic is very simple:

Xiao RP2040 Pin D0 --> Oscilloscope Probe CH2 --> 1k Resistor --> Oscilloscope Probe CH1 --> 105nF Capacitor --> RP2040 GND 

This allows us to measure the PWM output before and after running through the resistor for smoothing.

We played around with the autoset, Manual adjustment, Comparisons and display modes.

Here’s the board setup:

And here’s the measurements we got.

First is the standalone sine wave:

And the comparison of smoothed with the resistor and unsmoothed:

Here’s a video playing around with the settings on the Oscilloscope: