Week 6, Electronics Design¶

Assignment¶

Group Assignment¶

Use the test equipment in your lab to observe the operation of a microcontroller circuit board (as a minimum, you should demonstrate the use of a multimeter and oscilloscope)
Document your work on the group work page and reflect what you learned on your individual page

Individual Assignment¶

Use an EDA tool to design a development board that uses parts from the inventory to interact and communicate with an embedded microcontroller

Checklist¶

from Nueval

Linked to the group assignment page
Documented what you have learned in electronics design
Checked your board can be fabricated
Explained problems and how you fixed them
Included original design files
Included your hero shots

Group work¶

For my group work I used testing equipment in the lab to probe a microprocessor. In that work, I utilized both a multimeter and oscilloscope to probe a microprocessor at points running code that blinked an LED. With the multimeter, I was able to test that LED was installed in the correct orientation. At one point, I had a faulty LED, which failed to light with power from the multimeter (tested in both current directions). The multimeter helped me determine that I needed to remove this LED and install another. With a blinking LED, I was able to see periodic signals on the oscilloscope. I feel that I gained some very basic appreciation on the power of these tools, yet there is much more to learn and greater power to be harnessed.

Individual work¶

Set up for electronics design¶

I am totally unfamiliar with electronics design. Based on my instructors recommendation, I watched a playlist of how to work with KiCAD on YouTube.

Installing KiCAD was done via Homebrew. Homebrew is a package manager for MacOS, which makes installation of programs easy. Common opensource programs are easily installed and updated via Homebrew. The simple command to install is brew install kicad.

I then installed the FabLab KiCAD library. I used the instructions seen in this video (in Icelandic).

Then, I was set to go with KiCad.

Board Design¶

With KiCAD installed, I began a journey to design a very simple board. To start, I made a project in KiCAD.

Then, the schematic editor is opened, and components are added here. I am plan to make a simple board that blinks an LED when a button is pushed. My microcontroller is a XAIO RP2040, and I added that to the schematic (using the A key as shortcut). This is available in the FabLab KiCAD library.

Then the RP2040 is placed on the schematics after selection.

The board also requires a LED, a resistor, and a button switch. Each of these is added to the schematic.

Then, the componenets need to be wired in the schematic. The resistor and LED are connected in series from pin #0 to a ground. Switch is connected to pin #1 and the ground.

The connected code which sets the pins to be used.

from machine import Pin
import sys,select,time

led_pin = 1
button_pin = 0

led = Pin(led_pin,Pin.OUT)
button = Pin(button_pin,Pin.IN,Pin.PULL_UP)

This is the basis of the chosen wiring.

With the components wired, I then opened the PCB editor functionality. The “Update PCB from schematic” command adds all the components and expected wiring from the schematic.

A critical aspect of wiring the schematic is using the schematic electrical rules checker to verify the schematic. Most specifically, this can check that all the pins and components are connected or designated as not being connected.

This results in all the components tightly placed together.

These need to be arranged with space for the board wiring. Thin blue lines show the places where wiring is needed on the board.

With “route single tracks” command (shortcut X), the blue wires are replaced with the needed connections.

It is then important to check the design with the PCB Design Rule Checker. I received several warnings about the text, but is only important to check for errors. I then turned off the warnings, and I have one error. I need to define the edge of my board.

With the rectangle tool, an edge was defined.

Rerunning the Design Rule Checker resulted in no errors. This simple board is ready for a fabrication test.

Here are the KiCAD files for this board.

Here are the design files which can be used for fabrication. The zip archive contains the Gerber files, which could be used for ordering from a PCB manufacturer. And an SVG filefor the front copper traces from the board. This can be used to set up a milling process.