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| Using ESP32 and Neo-7N for precise frequency measurement |
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| edigi:
--- Quote from: ogden on September 13, 2018, 12:06:12 pm --- --- Quote from: edigi on September 13, 2018, 11:50:54 am ---Note: multi channel high frequency measurement can have issues due to the massive amount of interrupts generated --- End quote --- This means that gating (timer capture) interrupts --- End quote --- Nope, gating is full HW without any interrupts, please try to read the specs before you make such bold statements and also there is no 32 bit counter either that you seem to miss also from my earlier post in this very topic (not to mention the spec again). |
| ogden:
--- Quote from: edigi on September 13, 2018, 12:34:29 pm --- --- Quote from: ogden on September 13, 2018, 12:06:12 pm --- --- Quote from: edigi on September 13, 2018, 11:50:54 am ---Note: multi channel high frequency measurement can have issues due to the massive amount of interrupts generated --- End quote --- This means that gating (timer capture) interrupts --- End quote --- Nope, gating is full HW without any interrupts, please try to read the specs before you make such bold statements --- End quote --- Oh my :palm: Please try to read as well. I said "gating (timer capture) interrupts". Don't you see timer capture mentioned? For someone familiar with hardware timers it shall be obvious what actually I did mean. I mean timer capture and it's following interrupt initiated by gate timer (hardware) signal. Comprehendo? --- Quote ---and also there is no 32 bit counter either that you seem to miss also from my earlier post in this very topic (not to mention the spec again). --- End quote --- I love when people create unnecessary problems just to struggle solving them. Some form of EE masochism? Why don't you just pick MCU with 32bit timer?! |
| edigi:
Let's cut this discussion short: I don't have any issue with the counting and it's precision (it's already 7-8 digits). The issue is that the gating signal currently from XCO does not have long term (due to e.g. aging) or even mid/short term stability (due to temperature change). Actually counting precision is so good that I can see even the sub KHz warm up drift of the signal in 2 GHz range. That is what the pps signal from GPS expected to solve as it has super long/mid term stability. |
| ogden:
--- Quote from: edigi on September 13, 2018, 01:25:20 pm ---That is what the pps signal from GPS expected to solve as it has super long/mid term stability. --- End quote --- You have other option as well - use 8MHz (or other integer ratio to 48 MHz), reciprocally measure your reference oscillator against GPS freq. Such way you possibly can have faster lock times after power-on. While local oscillator is not locked, you can use GPS freq as reference frequency source. |
| edigi:
--- Quote from: ogden on September 13, 2018, 01:42:52 pm --- --- Quote from: edigi on September 13, 2018, 01:25:20 pm ---That is what the pps signal from GPS expected to solve as it has super long/mid term stability. --- End quote --- You have other option as well - use 8MHz (or other integer ratio to 48 MHz), reciprocally measure your reference oscillator against GPS freq. Such way you possibly can have faster lock times after power-on. --- End quote --- OK, it can be done, not exactly the way as you've described (as internal XCO is not surprisingly also the measurement limit + I'd like to stick to ready made dev board, without extra discrete components, and also there is no easy access to the internal XCO signal in case of most boards as due to WiFi there is shielding) but I can measure in this way the gating precision and correct based on that, all SW again). A bit of flexibility gained probably but via some more complexity (not much by its own, but I have many other things to do as well). I'll decide when the GPS module arrives if it worth for my case the extra effort. I also would not like to loose the possibility of WiFi as it can have also its own advantages (like wireless logging, control etc). |
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