Hello TNutters, maybe new thread?
you can have a look at two specsheets of the MT3339 chipset on my FTP-site 1) http://nixie.ramdac.be/TNutstuff/MT_IT530_Data_Sheet_rev_1_0.pdf on page 8 "PPS output 100 ms high pulse, rising edge +/-1 μs @ full second GPS epoch..." so it states +/-1 μs 2) http://nixie.ramdac.be/TNutstuff/gtop module application note -a00 _mt3339 series_.pdf on page 32 "The accuracy level of 1PPS for GlobalTop GPS module is within 100ns (same for majority of MTK GPS modules). The reference design below can help improving this accuracy to within 80ns." but on page 14 "1PPS signal is an output pulse signal used for timing application, its electronic characteristic are listed below: 1PPS signal and its pulse width with 100ms duration Low Voltage level: 0~0.4V High Voltage level: 2.8~3.1V Duration: 100ms (Firmware customization for duration is available) Period: 1s Accuracy (jitter):10ns" So what shall we believe? The rest of the PDF's make a good read. 73's Jacques Message: 4 Date: Fri, 23 Nov 2012 16:44:27 +0100 From: Jacques Tiete <[email protected]> To: "[email protected]" <[email protected]> Subject: Re: [time-nuts] time-nuts Digest, Vol 100, Issue 95 Message-ID: <[email protected]> Content-Type: text/plain; charset=us-ascii About: { Date: Thu, 22 Nov 2012 22:26:24 +0100 From: Fabio Eboli <[email protected]> To: [email protected] Subject: [time-nuts] MT3339 chipset in Globaltop's FGPMMOPA6H Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1; DelSp="Yes"; format="flowed" Hello, while asking info about the FE5682, I realized that for another project (model plane data logging) I will buy some cheap gps modules built around an MT3339 chipset. In my mind somewhere I stored the fact that in the datasheet of these module is mentioned the pps output, so I checked and the manufacturer is claiming that it has "High accuracy 1-PPS timing support for Timing Applications (10ns jitter)" This is the module I'm talking about: http://www.mirifica.it/store/gps/342-globaltop-fgpmmopa6h-pa6h.html http://www.alcom.be/binarydata.aspx?type=doc/GTop-FGPMMOPA6H-Datasheet-V0A.pdf Has anybody used this chipset or similar for GPSDO? I have no experience with discipled oscillators but if there is any hope that the pps out of these modules is good for the task maybe it's time for me to start reading more about the subject. The final goal will be to check the timing of the Rb I have around. Thanks, Fabio. } Hello TNutters, I did some test with this module from Adafruit (http://www.adafruit.com/products/746) and it seems not a bad unit. Tested it together with my TBolt and the PPS seems quite stable most of the time, I did not do any logging and math on the result, just letting the TBolt trigger the scope and apart from the cable offset I guess 80% of the time the module was within 10 to 15 ns. However the specs are not very clear and it is a typical chip for mobile use in eg. carnav stuff. I also saw some other specs where the jitter was specified as 100ns. and even one with a 1 microsec. so I'm a little confused. As soon as I have some time I plan to connect this module to a BeagleBone and do some testing for an NTP server I think the Beagle is better for this than the RaspBerry because of the "real" ethernet port. Greetz, Jacques Tiete 0499 99 83 78 [email protected] Op 23-nov.-2012 om 00:19 heeft [email protected] het volgende geschreven _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
