Re: [time-nuts] teensy as time capture device
On 9/24/15 11:02 AM, Hal Murray wrote: xne...@luna.dyndns.dk said: External Oscillator (the system clock clock) , or External Timer clock (limited to system clock/4) That sounds like they are running the external signal through a synchronizer and then doing all the logic on the system clock. That would add a lot of high frequency jitter but work as expected at longer time scales. It would be fun to see if you could pick up hanging-bridge type artifacts. Almost certainly. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] teensy as time capture device
On Thu, September 24, 2015 7:30 am, Jim Lux wrote: > What would be interesting is if there's a pin on the Arduino/Teensy that > you could feed a high quality oscillator to, and then do counting with > that. The K20 microcontroller has a mindbendingly large number of > features and alternate pin functions. The Beaglebone Black has that feature. I have been trying to figure out if having both the 10MHz to drive the counter and the PPS latching the count fed from the same Thunderbolt might cause some kind of systematic offset similar to a hanging bridge effect. Any guess? -- Chris Caudle ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] teensy as time capture device
In message <5602f65b.6050...@earthlink.net>, Jim Lux writes: >I've got a teensy3.1 hooked up to a 33120 function generator (not >exactly a super stable device) and generating period data for a 1 Hz >square wave. That is actually a particularly bad way of doing it, because the 33120 will generate a sine and run it through a zero-detector. You get much better performance by defining a ARB function which is a square. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] teensy as time capture device
On Thu, 24 Sep 2015 05:30:35 -0700, Jim Lux wrote: > > What would be interesting is if there's a pin on the Arduino/Teensy that > you could feed a high quality oscillator to, and then do counting with > that. The K20 microcontroller has a mindbendingly large number of > features and alternate pin functions. As i see it, from the DS. , it seems like there are 2 options. External Oscillator (the system clock clock) , or External Timer clock (limited to system clock/4) Electr. specs https://www.pjrc.com/teensy/K20P64M72SF1.pdf Family Ref https://www.pjrc.com/teensy/K20P64M72SF1RM.pdf Seems like the EXTAL pin (main oscillator) accepts an Oscillator signal (max VDD + 0.3v) (Electr specs pg.10) Ext Osc Connection (Family ref. pg. 526) Also see PLL jitter (Electr specs pg.27 table 14) There is a possibility to clock the FlexTimerModule by an external clock (FTM_CLKIN/EXCLK - Max freq is Mainclock/4) , see (Family Ref. pg. 113, 214 & 774) If using EXTAL and USB , you want to make sure that the USB part still gets it's 48Mhz (via the PLL mul/div). Maybe divide 10Mhz (XTAL) by 2 , and mul by 48, in the PLL. Rgds CFO - Denmark -- E-mail:xne...@luna.dyndns.dk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] teensy as time capture device
On 9/24/15 7:13 AM, cfo wrote: On Thu, 24 Sep 2015 05:30:35 -0700, Jim Lux wrote: What would be interesting is if there's a pin on the Arduino/Teensy that you could feed a high quality oscillator to, and then do counting with that. The K20 microcontroller has a mindbendingly large number of features and alternate pin functions. As i see it, from the DS. , it seems like there are 2 options. External Oscillator (the system clock clock) , or External Timer clock (limited to system clock/4) Electr. specs https://www.pjrc.com/teensy/K20P64M72SF1.pdf Family Ref https://www.pjrc.com/teensy/K20P64M72SF1RM.pdf Seems like the EXTAL pin (main oscillator) accepts an Oscillator signal (max VDD + 0.3v) (Electr specs pg.10) Ext Osc Connection (Family ref. pg. 526) Also see PLL jitter (Electr specs pg.27 table 14) There is a possibility to clock the FlexTimerModule by an external clock (FTM_CLKIN/EXCLK - Max freq is Mainclock/4) , see (Family Ref. pg. 113, 214 & 774) If using EXTAL and USB , you want to make sure that the USB part still gets it's 48Mhz (via the PLL mul/div). Maybe divide 10Mhz (XTAL) by 2 , and mul by 48, in the PLL. I would think that the FTM_CLKIN would be the way to go.. keep the core running at 48 and run 10 MHz in as EXCLK (since it's less than Mainclock/4) Not sure I'd want to fool with the PLL programming: that's something where there might be other stuff that makes assumptions about how it's configured. Now I have to look if the right pins come out to something I can see. This is the MK20DX256VLH7 configuration. Only FTM1 (0,1) and FTM2 (0,1) are configured I think. "There are two external FTM_CLKINx pins that can be selected by any FTM module via the SOPT4 register in the SIM module." Looks like pin 32 and 33 on the chip Tnx Jim ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] teensy as time capture device
xne...@luna.dyndns.dk said: > External Oscillator (the system clock clock) , or External Timer clock > (limited to system clock/4) That sounds like they are running the external signal through a synchronizer and then doing all the logic on the system clock. That would add a lot of high frequency jitter but work as expected at longer time scales. It would be fun to see if you could pick up hanging-bridge type artifacts. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] teensy as time capture device
I've got a teensy3.1 hooked up to a 33120 function generator (not exactly a super stable device) and generating period data for a 1 Hz square wave. The period is in "ticks" of the 48 MHz clock, so my thinking is that if I hook up a good 1pps, what I'm really measuring is the frequency of the CPU clock, so I can just accumulate some data, and then load it into timelab. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
