GitHub - idlehandsdev/pps-watch: An extremely accurate watch that doesn't tell time. · GitHub
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idlehandsdev
pps-watch
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PPS Watch
The Most Accurate Watch that Doesn't Tell Time.
What it does
Receives GPS , achieves position/time fix
Outputs 1PPS (one pulse per second) on the GPS module's hardware TIMEPULSE pin, silent until locked, active at 1Hz once locked
Distributes that PPS signal across a BNC connector via buffered outputs
Accepts an external PPS reference, compares it against the GPS PPS via a hardware XOR phase comparator, with LED indicators for PPS presence and phase offset
No microcontroller. No firmware. The GPS module's hardware PPS pin drives the LEDs and BNC outputs directly through logic buffers.
Hardware
GPS module: u-blox MAX-M10S
Antenna: External via SMA, no onboard antenna. Direct-mount stub antennas (Quectel YEGT001AA right-angle / YEGT002AA straight) screw directly onto the SMA connector, no cable
Buffering: 2x 74HC125 quad buffer (GPS output side, external input side)
Comparator: 74AHC1G86 single XOR gate
Indicators: 0805 SMD LEDs -- 1x red (PPS), 2x green (fix / external PPS)
Power: CR2450 coin cell, switched via SW1, V_BCKP always connected
Config port: Qwiic (I2C) for one-time setup via u-center if needed
Connectors: 2x BNC, 1x SMA (antenna), 1x Qwiic
See the schematic for full signal flow and the BOM for part numbers.
CAD
This is a KiCad project. PCB mechanical design and 3D assembly were done in Fusion 360.
Fusion 360 share link: https://a360.co/4xXmWnG
BOM
** BOM needs updated missing a few components! - https://www.digikey.ca/en/mylists/list/XIH163JVIJ
Watch Assembly
3D Printed Parts
Print the following files from the CAD/ folder:
CAD/pcb_frame_mount.stl -- frame that holds the PCB
CAD/watch_band_mount.stl -- mounts the band to the frame
Watch Band
Any standard 22mm watch band works. Tested with:
Bandini Nylon Sports Watch Band Strap 22mm
Hardware
2 x M2x6mm Flat Head Plastic Threading Screws to mount body to strap mount. - https://www.mcmaster.com/90485A415/
2 x M3x6mm Pan Head Plastic Threading Screws for mounting PCB to Body - https://www.mcmaster.com/99461A939/
2 x M3x35mm Round Head Machine Screws to mount strap. Just Thread into the plastic snugly https://www.mcmaster.com/92000A134/
Felix Corp -- Idle Hands Dev R&D Division<br>Asset Tag: FC-IDH-UTC-001
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An extremely accurate watch that doesn't tell time.
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AGPL-3.0 license
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