[time-nuts] PIC processor CTMU module used for sub-ns TIC applications?
I see Microchip application note AN1375 at http://ww1.microchip.com/downloads/en/AppNotes/01375a.pdf suggests that the CTMU module included in some recent PIC parts, for example PIC18F46J11 can be used as a TIC building block for interpolating time intervals with sub-ns resolution. I gather this module was originally designed for touch sensing applications; they also mention measurement of absolute and relative capacitance. The application note merely asserts the possibility, but neglects to present a specific design. Has anyone here attempted to use a PIC CTMU in that way? I've been studying Richard McCorkle's PICTIC-II design (1) with an eye to implementing the digital parts in a CPLD, and so far have a start/stop counter working (2). I haven't yet started on the analog part of the circuit, but now I'm wondering if Microchip has already done the work for me, in a $4 part ? (3) (1) http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:pictic (2) http://bealecorner.org/best/measure/time/CPLD-TIC/ (3) http://parts.digikey.com/1/parts/1671850-ic-pic-mcu-flash-64kb-44-tqfp-pic18f46j11-i-pt.html ___ 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] PIC processor CTMU module used for sub-ns TIC applications?
Le 17/04/2011 00:20, beale a écrit : The application note merely asserts the possibility, but neglects to present a specific design. Has anyone here attempted to use a PIC CTMU in that way? The app note doesn't give a complete design, but the principle of precision time measurement is explained with a corresponding block design under Precision Time Measurement. It relies on A/D sample and hold capacitor charging between 2 edge detections. Worth looking into though. I expect the data sheets will show how to implement it and define its limitations. ___ 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 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] PIC processor CTMU module used for sub-ns TIC applications?
beale wrote: I see Microchip application note AN1375 at http://ww1.microchip.com/downloads/en/AppNotes/01375a.pdf suggests that the CTMU module included in some recent PIC parts, for example PIC18F46J11 can be used as a TIC building block for interpolating time intervals with sub-ns resolution. I gather this module was originally designed for touch sensing applications; they also mention measurement of absolute and relative capacitance. The application note merely asserts the possibility, but neglects to present a specific design. Has anyone here attempted to use a PIC CTMU in that way? I've been studying Richard McCorkle's PICTIC-II design (1) with an eye to implementing the digital parts in a CPLD, and so far have a start/stop counter working (2). I haven't yet started on the analog part of the circuit, but now I'm wondering if Microchip has already done the work for me, in a $4 part ? (3) (1) http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:pictic (2) http://bealecorner.org/best/measure/time/CPLD-TIC/ (3) http://parts.digikey.com/1/parts/1671850-ic-pic-mcu-flash-64kb-44-tqfp-pic18f46j11-i-pt.html Spotted that feature several months ago. It should work well to within the limits of the CTMU module design. IIRC the external capacitance needs to be kept low for sub ns resolution. Crosstalk from within the PIC chip as well as ground and Vcc bounce may be an issue. A statistical fill the buckets linearity test will allow evaluation the integral and differential nonlinearities in such a TDC. In this case a relatively unstable source is required to enable such testing. One of the resistance tuned silicon oscillators available from LTC and elsewhere should work well. Bruce ___ 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] PIC processor CTMU module used for sub-ns TIC applications?
In message 4daa7be5.5060...@sfr.fr, cook michael writes: Le 17/04/2011 00:20, beale a =E9crit : The application note merely asserts the possibility, but neglects to present a specific design. Has anyone here attempted to use a PIC CTMU in that way? I tried it when I had a pic18f25j50 in my breadboard anyway, but failed to get reliable results. If you want to play with it, I suggest you make an actual PCB and clean/coat it very carefully to avoid leaking current or electrostatic fields. -- 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.
