

Simplest cpu
A collection of PCBs that I've made for various projects.
- Size
- 85.7 × 54 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 100
- Nets
- 119
- Pads
- 472
- Tracks, vias
- 1,698, 170
- Pours
- 1
- Routed
- Yes
- KiCad
- KiCad 7 (file 20221018)
- Created
- 5 Nov 2022
- Updated
- 13 Mar 2023
Overview
Simplest cpu is an open-source printed circuit board by bweston6, from the bweston6/pcbs repository on GitHub. It is a 2-layer board of 85.7 × 54 mm with 100 parts on 119 nets, routed with 1,698 tracks and 170 vias.
It is built around the 74HC245D, SA39-11EWA and 74HC273D, with the 74HC86D, 74HC164 and 74LVC3G14DC among its other parts. Its parts include 51 resistors, 24 diodes, 17 ICs, 4 switches and 3 capacitors.
Main components
674HC245D
SO-20-300mil-40℃~+125℃ 1 160uA 2V~6V 7.8mA 7.8mA 74HC 8 9ns@4.5V,50pF Bidirectional Tri-State SOIC-20-300mil Buffers, Drivers, Receivers, Transceivers ROHSNexperiaBuffers, Drivers, Receivers, TransceiversSA39-11EWA
DIP-100.39 1 13mmx10mmx7mm 7 Segment 75mW Common Anode Red DIP-10 LED Segment Displays ROHSKingbrightLED Segment Displays74HC273D
SOIC-20-300mil-40℃~+125℃ 1 12ns 15ns@4.5V,50pF 2V~6V 3.5pF 30MHz 3ns 74HC Series 8 8uA D-Type Reset Rising Edge SO-20-300mil Flip Flops ROHSNexperiaFlip Flops74HC86D
SO-14-40℃~+125℃ 1.5V~4.2V 20ns@6V,50pF 2V~6V 2uA 4 5.2mA 5.2mA 500mV~1.8V 74HC Series XOR Gate SOIC-14 Logic Gates ROHSNexperiaLogic Gates74HC164
SOP-140℃~+70℃ 1 24ns@5V,16pF 2V~6V 74HC 8 Serial-to-Parallel SOP-14 Shift Registers ROHSGRShift Registers74LVC3G14DC
VSSOP-8-0.5mm-40℃~+125℃ 1.65V~5.5V 2.4ns@5.5V,50pF 24mA 24mA 3 4uA 74LVC Schmitt trigger VSSOP-8-0.5mm Inverters ROHSNexperiaInverters
README
README.mdPCBs
PiKVM
The PiPVM project requires some additional hardware for ATX system control.
This PCB implements the circuit from this section: https://github.com/pikvm/pikvm#setting-up-the-v2 in a Raspberry Pi uHat footprint, per the specification at https://github.com/raspberrypi/hats.

Parts
100| Qty | Value | Footprint | References |
|---|---|---|---|
| 32 | 4K7 | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R10, R11, R12, R13, R14, R15, R16, R23, R24, R25, R26, R27, R28, R29, R30, R31 +16 |
| 24 | LED | LED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolder | D1, D2, D10, D11, D12, D13, D14, D15, D16, D17, D18, D19, D20, D21, D22, D23 +8 |
| 19 | 10K | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R1, R2, R3, R4, R5, R17, R18, R19, R20, R21, R22, R39, R40, R49, R50, R51 +3 |
| 4 | 74HC245 | Package_SO:TSSOP-20_4.4x6.5mm_P0.65mm | U5, U6, U7, U12 |
| 3 | SA39-11EWA | Display_7Segment:Sx39-1xxxxx | U9, U10, U11 |
| 2 | 1uF | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C1, C3 |
| 2 | 74HC273 | Package_SO:TSSOP-20_4.4x6.5mm_P0.65mm | U1, U2 |
| 2 | 74HC86 | Package_SO:TSSOP-14_4.4x5mm_P0.65mm | U16, U17 |
| 2 | 74LS283 | Package_DIP:DIP-16_W7.62mm | U3, U8 |
| 1 | 330nF | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C2 |
| 1 | 74HC164 | Package_SO:TSSOP-14_4.4x5mm_P0.65mm | U14 |
| 1 | 74LS08 | Package_SO:TSSOP-14_4.4x5mm_P0.65mm | U13 |
| 1 | 74LVC3G14 | Package_SO:SSOP-8_2.95x2.8mm_P0.65mm | U4 |
| 1 | Battery_Cell | Battery:BatteryHolder_Keystone_3034_1x20mm | BT1 |
| 1 | Clock | Button_Switch_Keyboard:SW_Cherry_MX_1.00u_PCB | SW3 |
| 1 | SST39SF020 | Package_LCC:PLCC-32_THT-Socket | U18 |
| 1 | SW_Coded_SH-7010 | Button_Switch_THT:Nidec_Copal_SH-7010C | SW5 |
| 1 | SW_DIP_x04 | Button_Switch_THT:SW_DIP_SPSTx04_Slide_6.7x11.72mm_W7.62mm_P2.54mm_LowProfile | SW2 |
| 1 | SW_DIP_x08 | Button_Switch_THT:SW_DIP_SPSTx08_Slide_6.7x21.88mm_W7.62mm_P2.54mm_LowProfile | SW1 |
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Questions
How big is the Simplest cpu PCB?
It measures 85.7 × 54 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Simplest cpu use?
100 parts, built around the 74HC245D, SA39-11EWA, 74HC273D and 74HC86D. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Simplest cpu KiCad files?
From the bweston6/pcbs repository on GitHub, at the commit this page was made from: the board is simplest-cpu/simplest-cpu.kicad_pcb and its schematic PiKVM uHat/PiKVM.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Simplest cpu design in my own project?
Its repository states no licence, so its author keeps all rights: ask bweston6 before reusing the design.