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google·mozc-devices·mozc-dial/board/main/main.kicad_pcb

Main PCB layout, top view — open source RP2040/RP2350 board by google

About the Main PCB

Main is an open source RP2040/RP2350 PCB design by google, published on GitHub under the Apache-2.0 license. It is a 2-layer board measuring 98 × 71 mm, with 102 components from 18 distinct parts.

Its main chip is the RP2040, from the RP2040/RP2350 family. Other key parts include the AMS1117-3.3, TBD62083AFNG, 74HC238 and W25Q128JVS. By type, the board carries 45 capacitors, 24 connectors, 14 ICs, 14 resistors, 3 switches and 2 crystals.

It belongs with the keyboards and sensors designs in this gallery.

From the project

Circuit diagrams and firmware source code for Gboard DIY keyboards

For the entire keyboard assembly, please refer to the Build Guide.

This explanation covers the case where all 3 bits are populated. However, for the 9-dial edition, some sensors may only require 1 or 2 bits. In that case, populate only the required number of components from the top (U1). For details, follow the instructions for the 9-dial edition.

Also, before making everything, it is recommended to check if the Gray code plate values can be read properly to reduce rework in case of problems. If it doesn't work well, populate resistors on R2, R4, and R6. For details, see Reading Sensor…

Main, from the project README
From the project README

Main components on the Main

AMS1117-3.3TBD62083AFNG74HC238RP2040W25Q128JVS

Main bill of materials (BOM)

102 components, 18 distinct parts — part numbers from the project's BOM.

QtyPartRefs
1
AMS1117-3.3
U101
5
TBD62083AFNG
U102, U103, U105, U107, U109
4
74HC238
U104, U106, U108, U110
2
RP2040
U201, U301
2
W25Q128JVS
U202, U302
2
12MHz_GND24
Y201, Y301
2
Conn_01x03
J102, J103
20
Conn_01x05_Pin
J106, J107, J108, J109, J110, J111, J112, J113 +12
2
USB_C_Receptacle
J201, J301
3
SW_Push
SW101, SW201, SW301
1
10u
C101
36
100n
C102, C103, C104, C105, C106, C107, C108, C109 +28
4
1u
C201, C209, C301, C309
4
20p
C210, C211, C310, C311
4
27.4
R201, R202, R301, R302
4
5.1K
R203, R204, R303, R304
4
1K
R205, R207, R305, R307
2
10K
R206, R306

Main design files

The KiCad project lives in the google/mozc-devices repository on GitHub; these links point at the commit this page was built from.

Main: common questions

What microcontroller does the Main use?

The Main is built around the RP2040, from the RP2040/RP2350 family.

How big is the Main PCB?

The Main measures 98 × 71 mm, has 2 copper layers and is 1.6 mm thick.

How many components are on the Main?

102 components, from 18 distinct parts, with part numbers taken from the project's own BOM. The full bill of materials is listed on this page.

Where can I download the Main design files?

From the google/mozc-devices repository on GitHub, which has the KiCad layout, the schematic and the BOM; the links under Design files point to each one.

Can I use the Main design in my own project?

Yes, under the terms of its Apache-2.0 license, which google chose for the repository.

Can I test firmware for the Main without the hardware?

Yes. HardLabs builds a simulation of the board from its netlist and BOM, so you can run and debug RP2040/RP2350 firmware against it before you order a PCB.

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