Does anybody make a GPS receiver IC or module that only outputs 1PPS? - Page 1
Forum section: electronics / rf-microwave

author: smoothVTer
author_rank: Regular Contributor
timestamp: December 07, 2016, 09:02:47 pm
content: I've been scouring Digikey and Mouser for a manufacturer/part that only outputs the 1PPS GPS time sync pulse. I don't need positional data, but I do need this 1PPS sync pulse. There are some modules I've found that can directly output 1PPS on an I/O, but they are either too expensive or too big/bulky because they are meant to be integrated into a beefy uC and have very many pins.Does anyone know of a module or RF receiver for GPS that is very basic, has a decent lock speed and only outputs 1PPS? Or something close to what I am looking for?

author: jpb
author_rank: Super Contributor
timestamp: December 07, 2016, 09:24:12 pm
content: I don't know of any modules that only put out 1pps but a fairly cheap module with an accurate 1pps (they claim 10nsecs) and a connector for an external aerial (which are all things I wanted) was the one by sparkfun/AdaFruithttps://www.proto-pic.co.uk/ultimate-gps-breakout-66-channel-w10-hz-updates-mtk3339-chipset.htmlThat is the UK source but as you're in the States you could get one directly from AdaFruit at a cheaper price:https://learn.adafruit.com/adafruit-ultimate-gps/downloads

author: metrologist
author_rank: Super Contributor
timestamp: December 07, 2016, 09:29:50 pm
content: Would one of these modules work for you?https://www.u-blox.com/en/product/lea-m8f-module

author: smoothVTer
author_rank: Regular Contributor
timestamp: December 07, 2016, 09:38:44 pm
content: Great suggestions so far, everyone.The MTK3339 is perfect price point: I wonder if they make something under 10mm X 10mm square.I looked at the uBlox products also ... woah, expensive! But they have the correct form factor I need.Same old story of $$$ vs. Features vs. Size

author: hagster
author_rank: Frequent Contributor
timestamp: December 07, 2016, 09:48:17 pm
content: They all output positional data. Time is just a byproduct of the position solution. Without position you cant lock the 1PPS to UTC.Some receivers will let you do tricks where you set the position as static in order to improve the timing accuracy, but thats just tweaking the nav solution filters.Dont expect to be able to buy a receiver that costs less or is smalller because it doesnt support position. In fact i would expect a dedicated GPS timing engine to cost more and be larger as the market for these requires expensive large ovenised oscilators etc etc to acheive really accurate timing.

author: mojoe
author_rank: Frequent Contributor
timestamp: December 08, 2016, 04:53:54 pm
content: For inexpensive boards with uBlox modules, look on ebay for Reyax. I have two different models and they work great. As far as I can tell, the two boards that I have are using real uBlox modules, not counterfeits.Some of the uBlox modules can be programmed to output a signal from 0.25 Hz to 10 MHz (or more). The default is 1 PPS. If you don't need or want the serial data, just ignore it. Using uCenter software, you can disable any and all output messages that you don't want.

author: @rt
author_rank: Super Contributor
timestamp: December 11, 2016, 01:01:54 pm
content: There are some surplus Ublox on eBay for about $8 AU at the moment.Minimal connection for default PPS output is pretty easy.

author: lincoln
author_rank: Regular Contributor
timestamp: December 23, 2016, 06:29:33 pm
content: We use this guy in our timeing products :http://www.gtop-tech.com/product-detail.php?id=4in volume it is 15$ in 1's 2's it is 20 ~25$

author: smoothVTer
author_rank: Regular Contributor
timestamp: December 24, 2016, 10:50:21 pm
content: Thanks everyone! A lot of great options here. When I get my system working, I will respond back to this thread and update my findings.

author: eb4fbz
author_rank: Regular Contributor
timestamp: December 24, 2016, 11:46:05 pm
content: If this is for a timming application you should look for a proper GPS timming receiver. They have special capabilities like internal TCXO, quantization error report and overdetermined mode for maximum timming stability.

author: lincoln
author_rank: Regular Contributor
timestamp: December 25, 2016, 03:36:24 am
content: It really depends on what you are doing, The biggest advantage in the space i work to timing receivers is the ability to operate in "position hold" mode. That allows the receiver to maintain time with only one SV, good timing results can be had with cheap modules as well. The plots compares an 80$ (at the time) ublox vs a 10$ gtop.

author: fcb
author_rank: Super Contributor
timestamp: December 25, 2016, 09:48:14 am
content: L76 by Quecteli use the L76L (built in LNA)

author: eb4fbz
author_rank: Regular Contributor
timestamp: December 25, 2016, 09:44:21 pm
content: For a good timming receiver: Trimble Resolution SMT or SMT 360 ($20-$30)VCTCXOAntenna status monitoring<15ns quantization error with reports for error compensationOverdetermined/possition hold mode...

author: cdev
author_rank: Super Contributor
timestamp: January 15, 2017, 10:38:56 pm
content: There are some new quite inexpensive multi-constellation chips from Skytraq that seem very electronics hobbyist friendly, and which also appear to have fairly good timing performance. They are sold as "navisparc" because they use and include the sparc risc processor. With some of their deals you get to use the CPU for your projects as well. If I didnt already have several GPSs and not enough time I would definitely be checking that out.

author: jimdeane
author_rank: Regular Contributor
timestamp: January 24, 2017, 05:10:02 pm
content: The QuarkNet cosmic ray muon detector uses a modified GPS module to produce that high-precision 1pps signal. I don't know how modified it is.Here is info about the old version:http://inspirehep.net/record/1377167/files/0311079v1.pdfThe current version (Series 6000) uses a NavSync GPS module. There is some info in the manual. search for 1pps for info on the current GPS implementation.http://faculty.ucr.edu/~ellison/Quarknet/6000CRMDUserManual.pdfUnfortunately, I don't know which NavSync module we currently use. Mine is deployed near the roof in a place I can't easily reach.