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7. Electronics Design

  • Individual Assignment

    • Redraw an echo hello-world board
    • Add (at least) a button and LED (with current-limiting resistor)
    • Check the Design Rules
    • Make it!
    • Test it
      • Extra credit: simulate its operation

  • Group Assignment:

    • Use the test equipment in your lab to observe the operation of a micro-controller circuit board

Research

PCB design software: Eagle

Assistant lecturer: Antti Mäntyniemi. He introduced the basics of PCB design and Eagle PCB design software.

Local Class, contains Tutorials

  https://gitlab.fabcloud.org/academany/fabacademy/2020/labs/oulu/local/-/wikis/Classes/Electronics%20design

fab.lbr library for Eagle: contains components used which can be used for FabAcademy.

https://gitlab.cba.mit.edu/pub/libraries/-/tree/master/eagle

Schematics, as a starting point for redrawing an echo hello-world board

http://academy.cba.mit.edu/classes/embedded_programming/t412/hello.t412.echo.png

SnapEDA: A Free PCB Footprints and Schematic Symbols

Not all required parts are in fab.lbr library.

Other required libraries/parts:

Eagle

Adding Library to Eagle

Eagle Control Panel:

  • Find the Directory for Libraries
    • Options > Directories
  • Copy the Library file into that directory

library-dir

Library Manager can also be used to check if the library is in use!

library-manager

SparkFun Connectors Library can be installed using the Library Manager.

sparkfun-connectors

Schematics

Start a new Schematic:

Eagle Control Panel:

  • File > New > Schematic

On Schematic, the following editor commands were used

ADD command

  • Function

    • Add elements into a drawing.
    • Add symbols into a device.

  • Mouse keys

    • Center mirrors the part.
    • Right rotates the part.

MOVE command

  • Function

    • Moves objects.

  • Mouse keys

    • Ctrl+Left selects an object at its origin or modifies it (see note).
    • Shift+Left selects the whole polygon (see note).
    • Ctrl+Right selects the group.
    • Left&Drag immediately moves the object.
    • Ctrl+Right&Drag immediately moves the group.
    • Center mirrors the selected object or the group.
    • Right rotates the selected object or the group.
    • Shift+Right reverses the direction of rotating.

DELETE command

  • Function

    • Deletes objects.

  • Mouse keys

    • Shift+Left deletes higher level object.
    • Ctrl+Left deletes a wire joint or a port.
    • Ctrl+Right deletes the group.

NET command

  • Function

    • Draws nets on a schematic.

  • Mouse keys

    • Right changes the wire bend style (see SET Wire_Bend).
    • Shift+Right reverses the direction of switching bend styles.
    • Ctrl+Right toggles between corresponding bend styles.

ERC command

  • Function

    • Electrical Rule Check.

Tools > ERC

Figure below shows the list of required components.

components

A video showing adding, moving and netting components in order to build the schematic. ERC command was used to check electrical rules.

Figure below shows the final schematic.

final-schematic

Board

  • Generate/Switch to board

board

  • Rearrange components using the MOVE command.
  • Use RATSNEST command to calculate shortest path.

  • Draw routed wires using ROUTE command.

    • Set the width to 16mil.
    • Make sure that you are on the Top layer.

route

  • Use DRC command to checks design rules.

DRC

  • Modify the size of the board

    • Dimension layer (Layer 20)

  • Use DIMENSION command to check design dimensions.

    • save some space for the 6 Pin header positioning.

  • Use POLYGON command to connect Ground:

    • Select Top Layer.
    • Select POLYGON and draw.
      • A POLYGON with a dashed line will appear.
    • Connect the polygon to ground by naming the polygon GND.
    • Click on RATSNEST.

A Video showing the board modifications.

The commands used and results are explained below:

RATSNEST command

  • Function

    • Calculates the shortest possible air-wires and polygons.

ROUTE command

  • Function

    • Converts un-routed connections into routed wires (tracks).

  • Mouse keys

    • Left starts routing from any given point along a pad, via, wire, or air-wire -OR* commits currently displayed intermediate route segments (and via, if layer changed).
    • Shift+Left starts routing with the same width as an existing wire -OR* places a via and continues routing on the same layer.
    • Center selects the next routing layer (and initiates via placement).
    • Shift+Center presents start layer selection dialog when starting from a multi-layer object.
    • Right toggles left/right direction of current bend styles.
    • Shift+Right cycles to the previous wire bend style.
    • Ctrl+Right cycles to the next wire bend style (see SET Wire_Bend).

DIMENSION command

  • Function

    • Adds dimensioning to a drawing.

  • Mouse keys

    • Center selects the layer.
    • Right changes the dtype.
    • Shift+Right reverses the direction of changing the dtype.
    • Ctrl+Left when starting/ending a dimension does not select an object.

POLYGON command

  • Function

    • Draws polygon areas.

  • Mouse keys

    • Center selects the layer.
    • Right changes the wire bend style (see SET Wire_Bend).
    • Shift+Right reverses the direction of switching bend styles.
    • Ctrl+Right toggles between corresponding bend styles.
    • Ctrl+Left when placing a wire end point defines arc radius.
    • Left twice at the same point closes the polygon.

DRC command

  • Function

    • Checks design rules.

Tools > DRC

The final PCB outline, after connecting the ground properly.

final

Outline

  • Set Layer to Milling (layer 46).
  • Draw the outline using Line command.

Outline must be thicker than the diameter of the milling tool Therefore, for a 1mm milling bit, outline width can be 40mil (=1.016mm). We had to rearrange elements and do ground again.

final-2

Exporting

To export the traces:

  • Set the background to black

option > User interface… > Layout > Background.

  • Hide all the layers except the Top layer

View > Layer settings

  • Export the image:

File > Export > Image.

  • Set the resolution to 2400dpi and select the monochrome.

To export the outlines:

Same as steps as traces, except:

  • Set Background to white.
  • Milling layer (layer 46) visible only.

Milling

Producing .rml files

Using Mods Mods

Making an .rml file (Circuit tracing)

traces

traces-2

Making an .rml file (outline)

outline

outline-2

Soldering

Board Soldered

soldering-2

Programming and Testing

Using the programmer board fabricated in Week 4 Electronics Production

connect

  • Upload echo.ino program
  • Connect the new board to the programmer

  • Audrino setup:

    • Tools > Board: “ATtiny412/402/212/202”
    • Port: [COM Port]
    • Programmer:”jtag2updi(megaTinyCore)”
    • Upload!

  • Connect the board to PC

connect

  • PuTTY setup:

    • Serial Line > [COM Port]
    • Speed > 115200

Programming-1

Programming-2

  • Observe the communication interface!

Programming-3

Files

Eagle Schematic and Board, PNG files and .rml files

https://gitlab.fabcloud.org/academany/fabacademy/2020/labs/oulu/students/yazan-barhoush/tree/master/docs/images/week07/individual/resources

Group Work

https://fabacademy.org/2020/labs/oulu/students/zhengya-gong/assignments/week06/#group-assignment_1