7. Electronics Design - Week 6¶

7.1. Assignments¶

Electronics Design

group assignment

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

extra credit: try another design workflow

extra credit: simulate your design

extra credit: design a case around your design

7.2. Group Assignment¶

TODO

7.2.1. Notes¶

Arduino
- not precice voltage, if from laptop

7.3. Individual Assignment¶

7.3.1. KiCAD¶

7.3.1.1. Tutorial Notes¶

KiCAD version 8 because in Version 9 SVG-Export does not work with the fab-libraries

Tutorial

7.3.1.1.1. General¶

VSS .. digital ground
VSSA .. analog ground (usually same ground as VSS)
R == Ohm
VDDA most more sensitive (analog voltage)
NRST .. Reset Pin, where N denotes negated
Crystal usually GND24 (ground on 2 and 4)
FootPrints .. physical layout of components used on PCB
- importend for buying parts and very importend for connectors

decopling capacitor

close to circuit
for small local energy storage
- e.g. when MCU switches, needs quick switch in transient of currents

Filtering

done by resistor, inductor, ferrite bead
- ferrite bead behaves resistant at a high frequency (e.g. 120Ohm at 100MHz)

USB

Power rails typically very noisy -> additional filtering (above)

Gerber Files/Manufacturer Output

on project -> export

7.3.1.1.2. Schematic Editor¶

General

Layout in different, logically fitting sections
Flags used to indicate for ERC (below)
- like e.g. PWR_FLAG used to indicate a power source from e.g. a filter actual power source

Keys

middle mouse .. Move plane
a .. (A)dd components
ESC .. Cancel KiCAD command
p .. add (P)ower component
- e on a component .. (E)dit component
w .. draw a (W)ire (connection)
double click on value symbol (C for capacity, R for resistance etc) .. edit value
double click on component -> click in footprint -> next to it ‘library’
r .. rotate
l .. add (L)able (help when creating a layout)
x/y .. flip symbol layout vertical/horizontal
q .. places ‘DO NOT CONNECT’ flag (used for rule-check)
m .. (M)ove selected components
‘Insert’-Key .. repeats (only?) dont connect
t .. insert (T)ext

Top Buttons

‘Annotate Schematics’-Button .. change labels of components automatically
‘Electrical Rules-Checker’ .. check for sanity of schematic (ERC)
‘Assign FootPrints’ .. choose the footprints used for your components
- in view, right-click on footprint -> view footprint
  - in view, top left ‘3D View’ (alt+3) -> opens 3D-Model of footprint with component
‘Bill of Material’ to generate Items needed for board

7.3.1.1.3. PCB Editor¶

General

first set board details, like how many layers, have powerlanes?,etc.
‘Ratsnest’ -> lines showing the connection not routed yet
for cutting the board, choose layer ‘Edge.Cuts’
- then just draw lines, those then cut the board
you can change the footprint of only the instance clicked on
- double click component -> ‘Edit FootPrint’
when near the MCU, try to ‘fin out’ the lanes, so that they are as far from each other
no vias on silkstream
copper zone solid pad -> prevent ‘Tombstoning’??
- help connectivity and lower inductions

Board Setup

top left ‘Board Setup’-button
Layers:
- Fab .. for assembling the board
- Silkscreen .. for text and outlines on the PCB
- Mask .. prevent solder bridging
- Cu .. copper layer
  - lower layer mostly power layer -> keep high from low voltage separated
Board finish
- Copper finish usually Gold -> ENIG .. Emersion Nickle Gold
Design Rules
- dependent on the producer
- IMPORTANT to copy those into KiCAD
Predefined Sizes
- can be used while editing
- good defaults: [IMAGE]

Keys

Alt+3 .. open (3)D-Viewer
m .. (M)ove components
Ctrl+Shift+m .. (M)easurement
r .. (R)otate
Shift+Leftklick .. select multiple, as usual
double click on component -> in 3d tab, you can change/add 3d models to footprints
Ctrl+Shift+z .. draw a filled zone, used for ground?
- set some settings for fill, select, which lane (e.g. ground)
- draw outline for zone
- when finished, press ‘b’
- left buttons ‘Draw Zone Fills’ and ‘Draw Zone Outline’ to toggle zone
x .. start routing
v .. make a hole to another layer and then x to create a trace, and v again to go back up, x to trace again (vxvx)