Week 6
Assignment - Electronics Design
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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 logic analyzer)
- Document your work on the group work page and reflect what you learned on your individual page
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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
Note: fabacademy page text adds:
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simulate a circuit
- check its design rules for fabrication
- extra credit: try another design workflow
- extra credit: design a case
KiCAD.
I decided to start with KiCAD.
I also followed this tutorial series, by @HTMWorkshop to familiarise myself with the interface.
I found and installed the KiCAD FabLib Library. Thanks Krisjanis, Miriam, Saheen and Aapo!
Drew Schematic
And, tadaa. 2 hours later:
1. Finding the right part...
The part I think I need is a 3-volt regulator, but from what I can determine in the library. There are a lot of similar ones.
So, I have a look at the datasheet.
Conclusion is that I'm more likely looking for a BD33FC0EFJ, or BD33FC0FP.
And the updated schematic (based on the example from the Datasheet) should look like this now:
2. Making your own symbol...
Save and close your schematic Editor. Open the Symbol Editor.
Go to File > New Library. And give it a name. You can choose whether it is available globally or just for this project.
Also, when you right-click, Pin Library is to keep it to the top in your various editors. Very handy.
Draw Rectangle, centred on the origin. Big enough to fit pins you're going to add. You can adjust the size later.Draw Pins (P),- Pin name: VCC, or GND, or SDA, or MOSI etc.
- Pin number: If you know, put it here. Keep it unique.
- Electrical type: Used in error-checking later, possibly SPICE export files.
- And then click
OK. The circle is where the wires attach, so the other end should touch the rectangle, with the label outwards. Placement isn't important, but convention seems to be GND connections at the bottom, and power at the top.
This is the item I want to draw up.
And using the steps above, I've added it as follows to the library:
And added it into the schematic:
Schematic to PCB
There is a button on the top menu, Update PCB From Schematic.
Initially your components import at the same location:
Drag them around. Use R to rotate, and try and untangle your components. The blue lines are your Rat's Nest, or Nets, that indicate the connections that need to be turned into your routed traces.
It seems that the missing Footprints warning, above - not only with the custom Symbols - may explain why many components haven't come through.
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I followed this post: How can i assign a footprint to a symbol?
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From the Schematic Editor, and then go to
Tools>Assign Footprints
Tip, keep the Preview panel open, while selecting from the list.
I didn't have a Footprint for the SSD1306 OLED panel that I drew the Symbol for. This was the closest. I am going to have to draw it.
In the meantime, this is already looking better:
Download the Xiao library from the Getting Started page:
Add Footprint library:
Routing
Apparently recent versions of Kicad have dropped support for autorouting. :(
So the rest of this was manual.
The shortcut to add a trace is X.
- First, I moved components, but that only got me a few routes;
- Then, I rotated components to the way that their nets indicated they wanted to be - a few more;
- Then, I rotated the screen upside-down - still 12(!);
- Then, went back to the Schematic Editor, and I changed GPIO14 to GPIO6, and so on - still 6...;
- Then I gave up on a one-sided board, but the only use of the second side is under the buttons, where I joined the like-legs to make them into a jumper!
And that was all! Fully routed!
Simulate
TODO
Check the Design Rules, check the Electronics Rules
TODO