Electronics design

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Design a development board to interact and communicate with an embedded microcontroller.

• Select and use software for circuit board design
• Demonstrate workflows used in circuit board design
• Explained problems and how you fixed them, if you make a board and it doesn't work; fix the board (with jumper wires etc) until it does work.
• Included original design files (Eagle, KiCad, etc.)
• Included a hero shot of your board
• Loaded a program and tested if your board works

Group assignment:

• Use the test equipment in your lab to observe the operation of a microcontroller circuit board (in minimum, check operating voltage on the board with multimeter or voltmeter and use oscilloscope to check noise of operating voltage and interpret a data signal)
• Document your work to the group work page and reflect on your individual page what you learned
• Link to the group assignment page.

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Group assignment

Now we're going to use this sketch (simple blink):

This version of the sketch is truly the simple blink sketch. It uses digitalWrite to write HIGH for 1 second and then LOW for 1 second to a pin:

							
// the setup function runs once when you press reset or power the board
void setup() {
	// initialize digital pin LED_BUILTIN as an output.
	pinMode(7, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
	digitalWrite(7, HIGH);   // turn the LED on (HIGH is the voltage level)
	delay(1000);                       // wait for a second
	digitalWrite(7, LOW);    // turn the LED off by making the voltage LOW
	delay(1000);                       // wait for a second
}
							
						

This sketch is slightly modified: It uses analogWrite to write an analog signal (number between 0-255) to a pin:

							
// the setup function runs once when you press reset or power the board
void setup() {
	// initialize digital pin LED_BUILTIN as an output.
	pinMode(7, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
	analogWrite(7, 128);   // 128 is the pwm signal
}
							
						

Here, we're connecting the oscilloscope to pin number 7 (as described in the sketch above) and to GND. You can see, that the oscilloscope measures the HIGH and LOW very accurately. Jumping from 0V to 3V3 every second as described in the code.

Trying to measure the same thing with the multimeter is very inaccurate.

What we can can conclude from this is that the multimeter and the oscilloscope excel in distinct areas. The oscilloscope is most effective for thoroughly examining signal complications and characteristics due to its wide-ranging capabilities. Meanwhile, the multimeter is useful for verifying errors after soldering or ensuring continuity. Furthermore, the multimeter is more user-friendly and can be set up much more rapidly than the oscilloscope.

_{End of group assignment}

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Board Features

I'm designing this PCB to work with my XIAO Seeduino SAMD21. To see its' features, go to my Embedded programming assignment. This SAMD21 can be programmed via USB and doesn't need pins for that. The following I/O-devices will have to connect to the board, since I want to use it for my final project:

• 2x HC-SR04 ultrasonic distance sensor
• 1x peristaltic pump

Also needed:

• 1x MOSFET to drive the pump
• 1x button to test its' functionality
• 1x 5V regulator
• Resistors, Capacitors, LEDs etc

My circuit needs different voltage supplies for the pump (12V) and the microcontroller (5V), but I only want to use one power supply. The solution is a 5V regulator. This component can be connected to any DC supply voltage between 7 and 35 volts. It has three pins: Pin one is the input for unregulated voltage. Pin 2 is the ground pin and pin 3 is the regulated 5 volt output. The manufacturer recommends a capacitor on the input and the output. It notes that the input capacitor is required if the regulator is far away from the power supply filter. The capacitor is going to help smooth out interruptions to the supply and also low frequency distortions.

The board also includes a programmable button and an LED that turn on on receiving power (plus the needed capacitors and resistors).

Designing the PCB in KiCad

Library preparation:

Creating a new project and working with it:

What to do after you added all of your components: From logic to layout

Download my KiCad project file