Part selection

• NMOS:
  • SI2302: €0.0062, SOT-23, https://jlcpcb.com/partdetail/Jsmsemi-SI2302/C5296725
  • JSM2301S: €0.0063, SOT-23, https://jlcpcb.com/partdetail/Jsmsemi-JSM2301S/C916399
  • 2N7002: €0.0074, SOT-23, https://jlcpcb.com/partdetail/Jsmsemi-2N7002/C916396
  • smaller packages: (sadly more expensive?)
    • SOT-323 == SC-70, SOT-563
    • VML0806 (€0.0556)
    • DFN0603
• Resistor: 1k(?), footprint 0402 (smallest)
  • €0.0005, https://jlcpcb.com/parts/basic_parts
• LED
• RAM chip
• Regfile chip?
• Clocking stuff

PCB Capabilities

https://jlcpcb.com/capabilities/Capabilities

• minimum via size?

  • hole: 0.15mm, diameter: 0.25mm

• minimum trace size?

  • width: 0.09mm, spacing: 0.09mm
  • do we ever need to care about the resistance?

• parasitic capacitance in wires, transistors, resistors, ...

• Figure out t_hold and t_setup!

  • analog SPICE simulation?

PCB cost estimate:

JLCPCB board cost: 400x100mm => 18.37 400x400mm => 73.46 300x200mm => 27.59 cost per mm2: 0.000459

SOT-23 size: 3.4x3.84 = 13.1 mm2 extra cost per SOT-23: 0.006

0402 size: 1.86x0.94 = 1.75 mm2 extra cost per 0402: 0.0008

Conclusion: board space costs the same as the component, double the price of everything (and some margin for routing space)

Resources

Kicad file format:

• https://dev-docs.kicad.org/en/file-formats/
• https://github.com/mvnmgrx/kiutils

Other similar kicad interactions:

• https://github.com/devbisme/skidl/blob/master/src/skidl/schematics/place.py
• https://github.com/devbisme/skidl/blob/master/src/skidl/schematics/route.py
• https://jeffmcbride.net/programmatic-layout-with-kicad-and-python/
• https://jeffmcbride.net/kicad-component-layout
• https://github.com/inventree/InvenTree

Place & Route algorithms:

• Intro placement in Rust: https://stefanabikaram.com/writing/fpga-sa-placer/
• Manhattan spanning tree: https://www.topcoder.com/thrive/articles/Line%20Sweep%20Algorithms

Final processor design

• 8/16/32 bit?
• RISCV? Something else? Something custom?
• RAM/ROM embedded or via pins?
• clock generation on-board?
• VGA out? audio out?
• GPIO pins?
• Leds?

Simulation

• logic level with custom waveform
  • TODO: show initial values, maybe offset the rest? think about how to offset LUTS and FFs in time, maybe stagger?
• net level with spice
  • caps, resistors, proper transistor models for timing analysis
• how to handle/express/constrain timing requirements?

Transistor level design

• resistor size? should we use difference ones depending on the situation?
• do we worry about buffers/fanout/stray capacitance?
• add async reset to FF
• global nets:
  • signals:
    • vdd, gnd
    • reset (or reset_pull)
    • clk (or clk_pull and (~clk)_pull)
  • layout:
    • plane for each? that's a lot of planes!
    • all on single shared plane, striped
    • all on 2 shared planes, striped/crossed?
  • make sure to add caps for gnd and vdd
  • make sure to add good clk tree