Week 07: Electronics Design

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Assignment

Group Assignment

Multimeter

We used a multimeter to do the continuity test of the hello-board as shown in the video. We turned the knob to select ohm and pressed the orange setup button to change the mode to make a beeping sound when two ends connect.

Power Supply

We used two jumper wires to connect the power supply machine to FTDI on the board. One wire connected to the ground pin and the other connected to VCC. In this case, the power supply replaces the FTDI connector.

Oscilloscope

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The introduction of the oscilloscope could be found here. An oscilloscope is an electronic test instrument that graphically displays varying signal voltages. By using it, we could know how electricity works in reality.

This video shows the voltage wave from the TX pin of a PCB which was programmed with the code by Kirs. It is sending 1 (pressed button) and 0 (released button) to the serial monitor. So what we see in the oscilloscope is the visualization of the 1 and 0 bytes.

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With the same program, we attached the oscilloscope pins on GND and LED. The different frequencies between the on and off of the button are obvious. While we pressed the button, the frequency of voltage went to 2 periods / 500ms, so that the LED blinked slowly. While the button was released, it boomed up to around 22 periods/ 500ms, which led to LED blinks really quick.

Individual Assignment

Demonstration

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1 3D view
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KiCAD

Preparation

This week we designed a PCB hello-world board by ourselves. KiCAD is free software that allows us to do it. To start the KiCAD smoothly, we need a library created by Krisjanis Rijnieks. Thank you, Kris

ATtiny412 is our starting point. For that we need the datasheet of it, we could find it here.

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The most important picture we need from the datasheet is this.

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Picture from SpenceKonde.

All the green pins are programmable. UPDI is a programing pin that we use for programming. PA6 and PA7 are also important because TX and RX stand for communication.

Setting for Library

  1. Preferences → Manage Symbol Library 1

  2. Preferences → Manage Footprint Library 1

  3. Preferences → Configure Paths 1

!Start

  1. Collect all the elements we need by Add and search by Fab+name. By right-clicking on the symbol, we can see Symbol Properties which include Datasheet, Footprint… andso on. 1

  2. Then start to specify all the connections by Wires and Labels. It’s an elegant way to connect the wires. During this procedure, we can check the picture from SpenceKonde that we showed before to understand the connection. 1 Hints: Labels need to connect on the end of Wires.
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  3. Once we have done this, we can see this. Red squares are the additional parts that I did for the assignment 1 Hints: TX and RX need to be swapped for correct communication between computer and chips.
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  4. To debug our board, we need to Annotate and Check electrical rules
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Hints: Add power flags on input and output to pass the electrical checker.
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  1. Assign PCB footprints
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  2. Generate Netlist and Open PCB editor
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  3. Puzzle time! We need to find out the best layout for our PCB by practice and experience. 1 Hints: Edit Net Classes into our bits thickness 1

  4. After continuously trying we got this!
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  5. Manage ground (GND) in the last step
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  6. Check the design rule and Ready to export
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  7. Export into the SVG file with margin
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  8. Follow the same procedure we did in week05, use mods to create the rml files. 1 1 1 1

  9. Milling with stronger bits is more efficient.

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  1. Soldering patiently and gently.
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Load a program and test my board

The setting up UPDI Programming Toolkit tutorial could be found from here.
Test file could be found from here.
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Confirm the connection of both PCBs.
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Download the megaTinyCore from the library.

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Select the correct board and programmer.

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Challenges

  1. Couldn’t find the power flag in the library.
    Solution: The power flag library could be found here.

  2. Wrong switch symbol.
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    Solution:
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  3. The mounting holes of the switch need to be drilled additionally.
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    Elegant Solution: pick out the yellow circles from the SVG file with Inkscape and create a rml file with mods to drill it with the CNC machine.
    Tips: Illustrator doesn’t work really well with SVG files.
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Download

The Week 07 zip file includes: