GPS Frequency Standard
Build V2
Stand-alone design does not require PC. Generates a 10 MHz output after satellite lock.
- NEO-7M GPS
- QTPy49 card
- CircuitPython code fits into QT Py (SAMD based) but a QT Py (RP2040 based) could be used
- 3.3V, 48 MHz
- Modified PulseGen card
- Oscillator circuit removed (not used as pulse generator)
- Receives input from GPS output and drives 50 Ohm output on BNC
- Status LED
- Blinks in for 1 second at power up
- Goes off until serial communications are working
- Blinks on-off as data is received from GPS while waiting for Satellite signal lock
- LED is on solid once output is enabled
- Fits into Aluminum Project Box Enclosure DIY 100*76*35mm - ebay search
- Inspired by Scullcom design
Wiring
| Signal | From | To | Color |
|---|---|---|---|
| GND | QTPy49 J4-1 | GPS pin 4 | Black |
| VCC | QTPy49 J4-2 | GPS pin 5 | Red |
| QTPy>GPS | QTPy49 J4-3 | GPS pin 2 | Blue |
| GPS>QTPy | QTPy49 J4-4 | GPS pin 3 | White |
| GND | QTPy49 J5-1 | PulseGen GND | Black |
| VCC | QTPy49 J5-2 | PulseGen VCC | Red |
| PPS | GPU pin 1 | PulseGen In | Purple |
| LED-VCC | QTPy49 J9-3 | D0 | Red |
| LED-GND | QTPy49 J9-1 | GND | Black |
Code
- FreqStdCap.ino - tool to generate bytestrings
- GPS_004.py - Final working code
- Saved as code.py to auto-run
- GPS_003.py - Capture data from GPS module a line at a time - helpful for debugging
- GPS_002.py - Read 32 bytes at a time
- GPS_001.py - Formatted stings output
Build V1
Requires PC running ublox software on PC to set output.
- NEO-7M GPS
- FTDI-49MM card set to 3.3V signal levels
- PulseGen modified to receive output from GPS and drive 50 Ohm output out of the box
- Fits into Aluminum Project Box Enclosure DIY 100*76*35mm - ebay search
GPS
- GPS Satellite Positioning Module NEO7M UBLOX
- Specifications:
- Working Voltage: 3.3v-5.0v
- Color: As Picture Shown
- Description:
- With micro USB interface, you can debug GPS module with ordinary phone data cable, no longer need to use USB-TTL and other tools.
- TTL interface is reserved to facilitate the use of USB-TTL or external microcontroller to control and receive GPS information.
- Ceramic antenna on module board, no GPS external antenna can be used to search for stars.
- Reserved SMA antenna interface, can use external antenna, star search ability is stronger.
Reference Materials
- Design & Build a GPS locked Frequency Standard- Scullcom
- SIMPLE 10 MHZ GPS FREQUENCY STANDARD AND RF GENERATOR
- uses Arduino Nano as FTDI replacement
- An Arduino-based GPS Disciplined Oscillator
- An Arduino Version of Brooks Shera's GPSDO
- Simulating the Brooks Shera (W5OJM) GPSDO Algorithm
Videos
