HardLabs

Lemon

rianadon·Cosmos-Keyboard-PCBs·lemon-wired/lemon-pcb.kicad_pcb

Lemon PCB layout, top view — open source RP2040/RP2350 board by rianadon

About the Lemon PCB

Lemon is an open source RP2040/RP2350 PCB design by rianadon, published on GitHub. It is a 2-layer board measuring 31.9 × 36 mm, with 49 components from 23 distinct parts.

Its main chip is the RP2040, from the RP2040/RP2350 family. Other key parts include the ZD25WQ80CTIGT, USBLC6-2SC6 and XC6206P332MR-G. By type, the board carries 17 capacitors, 13 resistors, 5 ICs, 4 connectors, 2 transistors and 2 switches.

It belongs with the keyboards designs in this gallery.

From the project

Open-Source keyboard PCB designs for the Cosmos Keyboard Generator

Notes for v0.0: Due to an error in routing, GP25 and GP11 got are in the wrong spot in the FPC connector (FPC1) to be compatible with the Skree PCBs. This is why they are swapped in the pinout and don't match the schematic. The reset button didn't get wired in the PCB, so to upload you need to hold down BOOT while plugging in the microcontroller.

In V0.3, the LED data pin (5V logic) is broken out as a pad in place of GP2 (3.3V logic).

Lemon, from the project README
From the project README

Main components on the Lemon

ZD25WQ80CTIGTUSBLC6-2SC6RP2040XC6206P332MR-G

Lemon bill of materials (BOM)

49 components, 23 distinct parts.

QtyPartRefs
1
ZD25WQ80CTIGT
U1
2
USBLC6-2SC6
U2, U5
1
RP2040
U3
1
XC6206P332MR-G
U4
1
Q_NMOS
Q1
1
Q_PMOS_SGD
Q2
1
12MHz
Y1
2
USB_C_Receptacle_USB2.0
J1, J2
1
Conn_01x11
J3
1
Conn_01x11
J5
1
Fingers
FPC1
1
Thumbs
FPC2
2
SW_Push
SW1, SW2
1
VIK Conn
VIK1
1
WS2812B-2020
D1
1
LED_Small
D2
10
100nF
C1, C5, C6, C9, C10, C11, C12, C13 +2
2
22pF
C2, C3
4
1uF
C4, C8, C16, C17
1
10uF
C7
Show 3 more
QtyPartRefs
4
1k
R1, R2, R7, R16
5
5k1
R3, R4, R10, R11, R14
4
27R
R5, R6, R8, R9

Lemon design files

The KiCad project lives in the rianadon/Cosmos-Keyboard-PCBs repository on GitHub; these links point at the commit this page was built from.

Lemon: common questions

What microcontroller does the Lemon use?

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

How big is the Lemon PCB?

The Lemon measures 31.9 × 36 mm, has 2 copper layers and is 1.6 mm thick.

How many components are on the Lemon?

49 components, from 23 distinct parts. The full bill of materials is listed on this page.

Where can I download the Lemon design files?

From the rianadon/Cosmos-Keyboard-PCBs repository on GitHub, which has the KiCad layout and the schematic; the links under Design files point to each one.

Can I use the Lemon design in my own project?

The repository has no license, so all rights stay with rianadon. Use it as a reference, and ask the author before reusing the design.

Can I test firmware for the Lemon 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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