HardLabs

JRWatch

jadenrhee·JRWatch·hardware/jrwatch.kicad_pcb

JRWatch PCB layout, top view — open source Nordic nRF board by jadenrhee

About the JRWatch PCB

JRWatch is an open source Nordic nRF PCB design by jadenrhee, published on GitHub. It is a 4-layer board measuring 36 × 36 mm, with 46 components from 24 distinct parts.

Its main chip is the C5118826, from the Nordic nRF family. Other key parts include the C7501206, BMI270 and USBLC6-2SC6. By type, the board carries 23 capacitors, 8 resistors, 4 ICs, 3 connectors, 2 switches and 2 diodes.

It belongs with the iot & wireless, wearables and displays & leds designs in this gallery.

From the project

Low-power BLE wearable: nRF52840 module + nPM1300 PMIC + BMI270 IMU + Sharp MIP display. 36 mm 4-layer board, ~15 µA projected sleep current, Zephyr firmware.

A smartwatch designed from scratch, board included. 36 mm across and 4 layers, with an nRF52840 for Bluetooth, an nPM1300 handling charging and the power rails, a BMI270 for motion, and a Sharp memory-in-pixel LCD that holds a static image on about 12 µW. Firmware runs on Zephyr.

Most of the design work went into idle current, meaning what it draws while sitting on a wrist doing nothing.

JRWatch, from the project README
From the project README

Main components on the JRWatch

C5118826C7501206BMI270USBLC6-2SC6

JRWatch bill of materials (BOM)

46 components, 24 distinct parts — part numbers from the project's BOM.

QtyPartRefs
1
C5118826
MDBT50Q-1MV2
U1
1
C7501206
nPM1300-QEAA-R7
U2
1
BMI270
U3
1
USBLC6-2SC6
U4
1
32.768KHZ
32.768kHz
Y1
1
TYPE-C-31-M-12
J1
1
C5139870
FH12A-10S-0.5SH
J2
1
SM02B-SRSS-TB
J3
1
C77131
10k NTC
RT1
1
C110293
PWR/SHIP
SW1
1
C110293
USER
SW2
1
ESD9B5.0
D1
1
ESD9B3.3
D2
2
2.2UH
2.2uH
L1, L2
6
10UF
10uF
C1, C2, C5, C7, C8, C12
1
2.2UF
2.2uF
C3
9
100NF
100nF
C4, C11, C13, C14, C15, C18, C19, C21 +1
5
1UF
1uF
C6, C9, C10, C20, C22
2
12PF
12pF
C16, C17
1
47K
47k
R1
Show 4 more
QtyPartRefs
1
150K
150k
R2
2
4.7K
4.7k
R3, R4
2
100K
100k
R5, R6
2
100R
R7, R8

JRWatch design files

The KiCad project lives in the jadenrhee/JRWatch repository on GitHub; these links point at the commit this page was built from.

JRWatch: common questions

What microcontroller does the JRWatch use?

The JRWatch is built around the C5118826, from the Nordic nRF family.

How big is the JRWatch PCB?

The JRWatch measures 36 × 36 mm, has 4 copper layers and is 0.8 mm thick.

How many components are on the JRWatch?

46 components, from 24 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 JRWatch design files?

From the jadenrhee/JRWatch repository on GitHub, which has the KiCad layout and the BOM; the links under Design files point to each one.

Can I use the JRWatch design in my own project?

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

Can I test firmware for the JRWatch without the hardware?

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

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