Difference between revisions of "GPS Frequency Standard"

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* Fits into Aluminum Project Box Enclosure DIY 100*76*35mm - [https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=100*76*35mm+aluminum&_sacat=0&LH_TitleDesc=0&_odkw=100*76*35mm+Aluminum+PCB+Instrument+Box+Enclosure+Electronic+Project+Case+Set&_id=174408274566 ebay search]
 
* Fits into Aluminum Project Box Enclosure DIY 100*76*35mm - [https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=100*76*35mm+aluminum&_sacat=0&LH_TitleDesc=0&_odkw=100*76*35mm+Aluminum+PCB+Instrument+Box+Enclosure+Electronic+Project+Case+Set&_id=174408274566 ebay search]
 
* Inspired by [http://www.scullcom.uk/design-build-a-gps-locked-frequency-standard-part-4/ Scullcom design]
 
* Inspired by [http://www.scullcom.uk/design-build-a-gps-locked-frequency-standard-part-4/ Scullcom design]
 
== Code ==
 
 
* Code runs on multiple CPUs on [[QTPy49]]
 
** [[QT Py (SAMD based)]] or
 
*** [https://www.seeedstudio.com/Seeeduino-XIAO-Arduino-Microcontroller-SAMD21-Cortex-M0+-p-4426.html?queryID=3273c05f7923d5ee5cbc677ce4892180&objectID=4426&indexName=bazaar_retailer_products SeeedStudio XIAO] or
 
*** [https://www.adafruit.com/product/4600 Adafruit QT Py]
 
** [[QT_Py_(RP2040_based)]]
 
*** [https://www.seeedstudio.com/XIAO-RP2040-v1-0-p-5026.html SeeedStudio XIAO]
 
*** [https://www.adafruit.com/product/4900 Adafruit QT Py]
 
* [https://github.com/land-boards/lb-Arduino-Code/blob/master/LBCards/GPSFreqStd/FreqStdCap/FreqStdCap.ino FreqStdCap.ino] - Tool that runs on Arduino to generate frequency bytestrings to send to GPS
 
* [https://github.com/land-boards/QT-Py/blob/main/CircuitPython/lbcards/GPS/GPS_004.py GPS_004.py] - Final working code
 
** Saved as code.py to auto-run
 
* [https://github.com/land-boards/QT-Py/blob/main/CircuitPython/lbcards/GPS/GPS_003.py GPS_003.py] - Capture data from GPS module a line at a time - helpful for debugging
 
* [https://github.com/land-boards/QT-Py/blob/main/CircuitPython/lbcards/GPS/GPS_002.py GPS_002.py] - Read 32 bytes at a time
 
* [https://github.com/land-boards/QT-Py/blob/main/CircuitPython/lbcards/GPS/GPS_001.py GPS_001.py] - Formatted stings output
 
  
 
== QTPy49 Card ==
 
== QTPy49 Card ==

Revision as of 08:04, 31 July 2022

GPS Freq Std P18490-720px.jpg

Build V2 Features

Stand-alone design does not require PC. Generates a 10 MHz output after satellite lock.

QTPy49 Card

GPS Card

  • 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.

GPS NEO-7M-03.PNG

50 Ohm Driver Card

Tindie-mediums.png

DRIVE50 P1080480-720PX.jpg

  • Uses DRIVE50 50 Ohm Driver
    • Able to drive long 50 ohm coax
    • 5 parallel 74AC14 outputs with 249 ohm series resistors on each output
    • Square wave output
    • Very fast edges
    • BNC is high quality (Amphenol) connector

Alternate (Original) Driver Design

  • Original design used modified PulseGen card to drive 50 Ohms at 3.3V level output
    • Remove oscillator circuit parts (R/C)
    • Only 1 BNC high quality (Amphenol) connector
    • Wire from GPS PPS pin attached as below
    • Use 1x2 pin header for power instead of 5MM Terminal Blocks

PulseGen Mod P18338-720px.jpg

  • Schematic

PulseGen Mods.PNG

Wiring

  • Dupont headers
    • GPS = 5-pin
    • LED = 3-pin
    • UART = 4-pin
    • DRIVE50 = 3-pin
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 DRIVE50 J1-3 GND Black
VCC QTPy49 J5-2 DRIVE50 J1-2 VCC Red
PPS GPU pin 1 DRIVE50 J1-1 In Purple
LED-VCC QTPy49 J9-3 D0 Red
LED-GND QTPy49 J9-1 GND Black

Build V1

Enclosure

  • Fits into Aluminum Project Box Enclosure DIY 100*76*35mm - ebay search
  • White-on-Black P-Touch labels

PulseGen P1080344-720px.jpg

Reference Materials

Videos