GPS Frequency Standard

Build V2

Stand-alone design does not require PC

• Hard coded 10 MHz output after lock
• NEO-7M GPS
• QTPy49 card
  • QT Py (SAMD based)
  • Running CircuitPython
  • 3.3V, 40 MHz
• PulseGen modified to receive input from GPS output and drive 50 Ohm output on BNC
• Fits into Aluminum Project Box Enclosure DIY 100*76*35mm - ebay search
• Inspired by

Wiring

# Wiring
# Signal   Color  From          To
# GND      Black  QTPy49 J4-1   GPS pin 4
# VCC      Red    QTPy49 J4-2   GPS pin 5
# QTPy>GPS Blue   QTPy49 J4-3   GPS pin 2
# GPS>QTPy White  QTPy49 J4-4   GPS pin 3
# GND      Black  QTPy49 J5-1   PulseGen GND
# VCC      Red    QTPy49 J5-2   PulseGen VCC
# PPS      Purple GPU pin 1     PulseGen In
# LED-VCC  Red    QTPy49 J9-3   D0
# LED-GND  Black  QTPy49 J9-1   GND

Code

• 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 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.

OLED Display

Description

• OLED display, no need backlight, self-illumination.
• The display performance is better than the traditional LCD display, also lower consumption.

Specifications

• Driver IC: SSD1306
• Size: 0.91 inch OLED
• Resolution: 128 x 32
• Size: 38 * 12 mm
• Number of pins: 4 Pin
• Interface Type: IIC interface
• Display Color: White
• Operating temperature:-40 ~ 85 ℃

I2C Pin Out

1. GND: Power Ground
2. VCC: Power + (DC 3.3 ~5v)
3. SCL: Clock Line
4. SDA: Data Line

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