Difference between revisions of "GPS Frequency Standard"

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== QTPy49 Card ==
 
== QTPy49 Card ==
  
 
+
* CPU choices are
 +
** [[QT Py (SAMD based)]]
 +
*** [https://www.adafruit.com/product/4600 Adafruit QT Py SAMD21 Product Page]
 +
*** [https://www.seeedstudio.com/Seeeduino-XIAO-Arduino-Microcontroller-SAMD21-Cortex-M0+-p-4426.html?queryID=3273c05f7923d5ee5cbc677ce4892180&objectID=4426&indexName=bazaar_retailer_products Seeeduino XIAO]
 +
*** 48 MHz
 +
** [[QT Py (RP2040 based)]]
 +
*** [https://www.adafruit.com/product/4900 Adafruit QT Py RP2040 Product page]
 +
*** [https://www.seeedstudio.com/XIAO-RP2040-v1-0-p-5026.html Seeed XIAO RP2040 Product page]
 +
*** 133 MHz
 +
** [[XIAO ESP32C3]]
 +
*** [https://www.seeedstudio.com/Seeed-XIAO-ESP32C3-p-5431.html?utm_source=mailchimp&utm_medium=edm&utm_campaign=bazaar_0707&ct=t%28%29&mc_cid=3303ccf0f9&mc_eid=e1825627f2 SeeedStudio XIAO ESP32C3] (New 2022-07)
 +
*** RISC-V Single Core
 +
*** Up to 160 MHz
 +
*** 400 KB SRAM
 +
*** 4 MB Flash
 +
*** 2.4GHz Wi-Fi subsystem
 +
*** [https://wiki.seeedstudio.com/XIAO_ESP32C3_Getting_Started/ Wiki]
 +
*** [https://files.seeedstudio.com/wiki/Seeed-Studio-XIAO-ESP32/esp32-c3_datasheet.pdf?ct=t()&mc_cid=87cf985ac5&mc_eid=1dd4876369 ESP32C3 Datasheet]
 +
* Connectors/Headers
 +
** DC Power
 +
** AD0 GVS
 +
** AD1 GVS
 +
** AD2 GVS
 +
** AD3 GVS
 +
** I2C with ground/VCC
 +
** TX/RX with ground/VCC
 +
** SPI with ground/VCC
 +
* QTPy49 can be powered from with either the USB C or DC jack
 +
** Automatic Schottky diode power switching between
 +
*** 5V from USB C
 +
*** 5V on external DC jack
 +
*** 7-12V on DC jack
 +
* 49x49mm ODAS form factor
 +
* (4) 4-40 mounting holes
  
 
== GPS ==
 
== GPS ==

Revision as of 08:02, 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.

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

Code

QTPy49 Card

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.

GPS NEO-7M-03.PNG

50 Ohm Driver

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

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