Difference between revisions of "EAGLE Style Guide"

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| Plug (most moveable connection part)
 
| Plug (most moveable connection part)
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| Potentiometer
 
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=Schematics=
 
=Schematics=
 
==Grid==
 
==Grid==

Latest revision as of 17:01, 1 August 2020

Part Creation

Symbol

Grid

  • Size: 0.1 in
  • Alt: 0.01 in

Name

  • Should be manufacturer part/family number (eg. ATTINY167-SU)

Description

  • Leave blank

Style

  • Origin
    • Center origin (crosshair) on symbol center
  • Text
    • Keep text horizontal
    • Size: 0.07 in
    • Line Distance: 50%
    • Font: proportional
  • Name
    • Locate in top left of symbol
    • Align: bottom-left
    • Layer: 95 Names
    • Value: >NAME
  • Value
    • Locate in bottom-left of symbol
    • Align: top-left
    • Layer: 96 Values
    • Value: >VALUE
  • Outline
    • Use Lines
      • Width: 0.01 in
      • Style: continuous
      • Layer: 94 Symbol
      • Curve: 0
    • Try to have a length/width that is a 0.1 in multiple (eg. 0.4 in by 0.4 in)

Functionality

  • Pins
    • Label pins to allow the symbol to be applied to parts in similar families
    • Name: Based on part datasheet
    • Direction: pas (passive)
    • Swap Level: 0
    • Length: middle
    • Function: none
    • Visible: both
  • Pin Placement
    • Power (VCC): top left
    • Ground (GND): bottom right
    • Inputs: left edge
    • Outputs: right edge
  • Passive Pins
    • Specifically resistors, capacitors, inductors, fuses, diodes
    • Visible: off
  • Connector Pins
    • Try to reuse an existing symbol for the size of connector
    • If need to make a new one, for pins:
      • Visible: pad
  • Decimal Labeling
    • For fractional values include the decimal point (eg. 3.3V, 4.5K)

Footprint

Grid

  • Size: 1 mm
  • Alt: 0.1 mm

Name

  • Should be manufacturer footprint name (eg. SOIC-20)

Description

  • Link to datasheet for part/family for pad layout

Style

  • Origin
    • Center origin (crosshair) on footprint center
  • Text
    • Keep text horizontal
    • Size: 1 mm
    • Ratio: 10%
    • Line Distance: 50%
    • Font: vector
  • Name
    • Locate in top left of footprint
    • Align: bottom-left
    • Layer: 25 tNames
    • Value: >NAME
  • Value
    • Locate in bottom-left of symbol
    • Align: top-left
    • Layer: 26 tValues
    • Value: >VALUE
  • Outline
    • Use Lines
      • Width: 0.2 mm
      • Style: continuous
      • Layer: 21 tPlace
    • Draw package outline per part/family datasheet
    • Used for part placement
  • Keepout
    • Use Rectangles
      • Layer: 39 tKeepout
    • Size 0.1 mm larger than the package
    • Used to prevent overlapping parts
  • Details
    • Capture more part details, extensions beyond outline, etc
    • Use
      • Width: 0.2 mm
      • Style: continuous
      • Layer: 51 tDocu

Functionality

  • Pad (Through-hole)
    • Name: name based on datasheet pin number
    • Diameter: auto
    • Drill: size based on datasheet
    • Shape: circle
    • Locked: unchecked
    • Thermals: checked
    • Stop: checked
    • First: unchecked
  • Smd (Surface Mount)
    • Name: name based on datasheet pin number
    • Smd Size: size based on datasheet
    • Layer: 1 Top (usually)
    • Roundness: 0%
    • Locked: unchecked
    • Thermals: checked
    • Stop: checked
    • Cream: checked
  • Polarity Indication
    • Through-hole
      • Make pin 1 visually different
      • Shape: square
    • Indicate polarity, when necessary
      • Prevents backwards installation
      • Direction or cathode indicators for diodes
      • Stripe or plus-minus for capacitors
    • Indicate Pin 1 for ICs
      • Use a circle (dot)
        • Width: 0 mm
        • Layer: 21 tPlace
        • Radius: 0.2 mm (at minimum)
    • Avoid overlapping pads with silkscreen, cut a section out

Device

Name

  • Should be manufacturer part number (eg. ATTINY167-SU)
  • Wildcards
    • Allows devices with multiple technologies (specifications) or packages
      • Uses wildcards in device name
      • Technology Name: *
      • Package Name: ?
    • Example
      • Regulator with two voltage (3.3V and 1.8V) technologies
        • AP2138N-3.3TRG1 for 3.3V
        • AP2138N-1.8TRG1 for 1.8V
        • Becomes AP2138N-*TRG1 with technology 3.3 and 1.8

Description

  • One sentence part function overview (valid for all variants)
  • Datasheet link

Value

  • Off unless its a passive part (resistors, capacitors, inductors, fuses, diodes)
  • If its a specific passive part with a value, add an attribute
    • Name: VALUE
    • Value: the value
    • Type: variable

Symbol

  • Use specific symbol for that part/family
  • Connectors are an exception
    • Generic symbol used for all connectors of a certain size

Footprint

  • Use specific footprint if unique
  • Try to reuse a footprint if it matches

Attribute (non-Passives)

  • Part number
    • Name: DKPN
    • Value: the Digi-Key Part Number (eg. ATTINY167-SU-ND)
    • Type: variable

Attribute (Passives)

  • Part number
    • Name: DKPN
    • Value: blank unless specific to part
    • Type: variable
  • Resistors
    • Should have tolerance and power ratings that is blank by default
    • Value is for resistance only
    • Tolerance
      • Name: Tolerance
      • Value: blank unless specific to part
      • Type: variable
    • Power
      • Name: Power
      • Value: blank unless specific to part
      • Type: variable
  • Capacitors
    • Should have tolerance and voltage ratings that is blank by default
    • Value is for capacitance only
    • Tolerance
      • Name: Tolerance
      • Value: blank unless specific to part
      • Type: variable
    • Voltage
      • Name: Voltage
      • Value: blank unless specific to part
      • Type: variable
  • Inductors
    • Should have tolerance and current ratings that is blank by default
    • Value is for inductance only
    • Tolerance
      • Name: Tolerance
      • Value: blank unless specific to part
      • Type: variable
    • Current
      • Name: Current
      • Value: blank unless specific to part
      • Type: variable
  • Fuses
    • Value is for current rating
  • Diodes
    • LEDs
      • Value should be color
    • Normal Diode
      • Value should be reverse voltage
    • TVS Diode
      • Value should be [Working Voltage]-[Breakdown Voltage] (e.g. 8V-8.5V)

Prefix

Chart for Prefix Designators
Letter Part Type
A Separate Assembly or Subassembly
C Capacitor
D Diode or LED
F Fuse
FB Ferrite bead
J Jack or Connector (least moveable connection part)
JP Jumper
K Relay or Contactor
L Inductor
LS/BZ Loudspeaker or Buzzer
M Motor
P Plug (most moveable connection part)
POT Potentiometer
PS Power Supply
Q Transistor
R Resistor
RN Resistor Network
S/SW Switch
T Transformer
TP Test Point
U Integrated Circuit
X Crystal
XF External Fuse

Schematics

Grid

  • Size: 0.1 in
  • Alt: 0.01 in

Sheets

Overall

  • Group related subsystems into a sheet
  • Have only 1 frame per sheet

Frames

  • A 11 x 17" frame with the following attributes
    • TEAM: RoboJackets team name
    • SCH_DESC: Short summary of content in the frame
    • REVISION: Schematic version
  • Group related subsystems into boxes
    • Use Lines
      • Width: 0.006 in
      • Style: shortdash
      • Layer: 97 Info
      • Curve: 0
    • Label using Text
      • Size: 0.07 in
      • Ratio: 8%
      • Line Distance: 50%
      • Font: proportional
      • Align: bottom-left
      • Layer: 97 Info

Description

  • Should match the SCH_DESC from the frame

Nets

Style

  • Text
    • Size: 0.05 in
    • Ratio: 8%
    • Line Distance: 50%
    • Font: proportional
    • Align: bottom-left
    • Layer: 97 Info

Signals

  • Should have a name if possible
  • Label every net:
    • Size: 0.05
    • Ratio: 8%
    • Font: proportional
    • Align: bottom-left
    • Layer: 95 Names
    • Xref: checked

Power

  • Use symbols with appropriate name as necessary
  • Label with the voltage range and max current at driver
  • Use Text

Busses

  • Should have a name and description
  • Use Text

Notes

Computed Values

  • Note values derived from a datasheet with a short explanation
  • Use Text within the box of the part in question

Specific Parts

  • Note optional parts
  • Note 0ohm isolation resistors and 0ohm jumper resistors
  • Use Text within the box of the part in question

Boards

Grid

  • Size: 1 mm
  • Alt: 0.1 mm

Board Fab

  • Load design rules before placement and routing
    • Allows spacing constraints to be known to tool
  • Check this repo for common EAGLE DRC files per fab

Placement

General

  • LEDs
    • Locate power status LEDs near power sources
  • Noise prevention
    • Keep analog electronics far from high power electronics
    • Provide adequate spacing for via stitching/shielding if needed
  • Decoupling capacitors
    • Recommended 1 per power pin on an IC
    • Place as close as possible to the power pin
    • Use multiple if necessary
      • Reduces noise
      • Place smallest value closest to the pin

Mechanical Considerations

  • Plan for board mounting holes
    • Figure out size of the hole and necessary clearance
    • Prevent components and traces from being near bolt heads
  • Plan for board cutouts and shape
    • Mark these before placement and routing
      • Use 51 tDoc / 52 bDoc to indicate cutout
    • Prevent components and traces from being near the cutout
  • Prevent components and traces from overlapping
    • Use 39 tKeepout / 40 bKeepout to block components
    • Use 41 tKeepout / 42 bKeepout to block copper and traces

Routing

General Practices

  • For two layer boards, try to keep components, signals, and power on the top layer and a ground plane on the bottom layer
    • Use Polygon
      • Width: 0.2mm
      • Cap: round
      • Layer: 16 Bottom
      • Curve: 0
      • Polygon Pour: solid
      • Spacing: 0.05
      • Isolate: 0
      • Rank: 1
      • Orphans: unchecked
      • Thermals: unchecked
  • Use extra internal layers when necessary
    • Allows for simplified power routing
    • Leaves more space for signal traces
    • Put power planes internally
      • Layer 2 and 15 on 4 layer boards
      • Layer 2, 3, 14, and 15 on 6 layer boards
  • Route signals orthogonally to avoid cross-talk between different layers (for boards >2 layers)
  • Differential signals
    • Do not split differentially routed pairs unless impedance and arrival time can be matched
  • High frequency
    • High frequency signals should have continuous low impedance return path directly beneath trace.
    • Keep high frequency signals isolated from other signals to minimize crosstalk

Traces

  • In general
    • Style: continuous
    • Cap: round
    • Curve: 0
  • Signals
    • Width: 0.3mm
  • Power
  • Avoid minimum sizing (based on the DRC) when possible

Vias

  • At minimum
    • Diameter: 0.65mm
    • Drill: 0.35mm
    • Shape: round
    • Layer: 1-16
  • Avoid minimum sizing (based on the DRC) when possible
  • Avoid vias on signals above 1GHz
  • Use the same number of vias on differentially routed traces

Silkscreen

  • Far more important than most people realize and can take a significant amount of time to get right
  • Makes a board easier to use, easier to debug, and harder to break

Style

  • Text
    • Size: 1 mm (at minimum)
    • Ratio: 8% (Important text can be bolded using 15%)
    • Line Distance: 50%
    • Font: vector
    • Layer: 21 tPlace / 22 bPlace
  • Markings (anything not already in footprints)
    • Will be in final board output
    • Use Lines
      • Width: 0.2 mm
      • Style: continuous
      • Layer: 21 tPlace / 22 bPlace
  • Extra Details
    • Will not be in final board output
    • Capture more details, extensions beyond outline, etc
    • Use Lines
      • Width: 0.2 mm
      • Style: continuous
      • Layer: 51 tDocu / 52 bDocu
  • Measurements
    • Will not be in final board output
    • Useful to mark critical distances
    • Can mark outer board dimensions
    • Use Dimension
      • Size: 2 mm
      • Ratio: 8% (Important dimensions can be bolded using 15%)
      • Layer: 47 Measures
      • DType: parallel
      • Line Width: 0.2mm
      • Ext. Line Width:v auto
      • Ext. Line Length: auto
      • Ext. Line Offset: auto
      • Unit: mm
      • Precision: 3
      • Show unit: checked

Labels

  • Label all power inputs with name and voltage (current optional)
  • Label all connectors with name
  • Label all switches with position values (e.g. on or off)
  • Label all debug LEDs (e.g. MCU Status)
  • Label all fuses with current rating

General

  • Aesthetics
    • Don’t place silkscreen on vias (even tented vias) unless absolutely unavoidable
    • Have your team logo on the board (e.g. RoboBuzz)
  • Versioning
    • Have a "vMAJOR.minor" version text label on the board (e.g. v2.1)
    • Have your team name and year on the board (e.g. RoboCup 2020)
  • Board ID
    • White square to allow for a board ID (e.g. written 2 means board 2)
    • Recommended if more than three boards will be fabricated
    • Use Rectangle
      • Make width and height 5mm by 5mm (minimum)
      • Layer: 21 tPlace / 22 bPlace