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Using ESP32 and Neo-7N for precise frequency measurement
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ogden:

--- Quote from: tggzzz on September 15, 2018, 08:24:32 pm ---See my previous messages. Read what they contain. Do not read what they don't contain.

--- End quote ---

You informed me well. When I will need hard realtime multicore MCU - I will look into xCORE. For simple tasks depending on various requirements I will use either msp430, AVR, stm32 or Zynq.

[edit] Don't worship chips. Actually don't worship anything. Get a life.
ogden:

--- Quote from: tggzzz on September 14, 2018, 09:32:51 pm ---How fast a data stream can you capture? While also doing USB connection to a host PC?

--- End quote ---

How many opamps and comparators xCORE MCU's have?

[edit] If you think you found "THE microcontroller" - you are mistaken.
tggzzz:

--- Quote from: ogden on September 15, 2018, 08:58:08 pm ---
--- Quote from: tggzzz on September 14, 2018, 09:32:51 pm ---How fast a data stream can you capture? While also doing USB connection to a host PC?

--- End quote ---

How many opamps and comparators xCORE MCU's have?

[edit] If you think you found "THE microcontroller" - you are mistaken.

--- End quote ---

Yet more strawman points. (Or perhaps you can point to where I claimed the xCORE devices are "THE microcontroller" - or anything vaguely similar)

Please stop wasting our time.
ogden:

--- Quote from: tggzzz on September 15, 2018, 09:37:31 pm ---
--- Quote from: ogden on September 15, 2018, 08:58:08 pm ---
--- Quote from: tggzzz on September 14, 2018, 09:32:51 pm ---How fast a data stream can you capture? While also doing USB connection to a host PC?

--- End quote ---

How many opamps and comparators xCORE MCU's have?

[edit] If you think you found "THE microcontroller" - you are mistaken.

--- End quote ---

Yet more strawman points. (Or perhaps you can point to where I claimed the xCORE devices are "THE microcontroller" - or anything vaguely similar)

Please stop wasting our time.

--- End quote ---

As you are not addressing my arguments, I do not want to waste my time addressing yours. Have a good time using just your affiliate chip.


--- Quote ---perhaps you can point to where I claimed the xCORE devices are "THE microcontroller"

--- End quote ---

When you carefully re-read your posts - you will see. In case you do not see how "fan boy" you are about xCORE, then I will have no further comments
edigi:
After some silence I've thought that I give some update about this project.

The ESP32 is suitable to create reciprocal frequency counter with exactly the 7-8 digit precision I was looking for.
For this one has to use one of the MCPWM capture feature + PCNT as counter.

The capturing is required so that:
- Gating for the counting can be made synchronous with the signal to be measured (so that one knows the amount of integer number of input signal cycles)
- The time between integer number of input signal cycles can be measured (in 12.5ns steps as capture counter is driven by a 80 MHz signal)

As the capture unit saves the actual value of the 12.5ns stepping capture counter in HW this is the resolution that can be achieved.
Thus for 7 digit resolution around 100ms measuring time is required and for 8 digits around 1 sec.  The precision is independent of the signal to be measured that can range roughly from 1/measuring time - 35 MHz (this was a bit higher with RMT gating).

As I have not figured out how to make a one shot capture triggering (if possible at all) very tight ISR timing is required so that the value captured by the HW is not overwritten by the next edge (next HW capturing). This seems to limit the upper frequency to 35 MHz down from the slightly higher theoretical limit (I'm actually even surprised that ~28.6ns is enough for the ISR to save the captured counter...). Also higher priority interrupts may interfere with this (not an issue for my hobby project, but for serious use it may be an issue).

Due to the capture functionality, measuring several cycles of the GPS 1pps signal could not be simpler. However I've also realized that GPS receiver is disturbed by the ESP32 RF noise, so that an active antenna that can be remotely placed is required (what I've received only recently).

So in short: While ESP32 may not be the best possible platform to make a precise reciprocal frequency counter, it's entirely possible with moderate cost.

More update later on, when I've explored this a bit more (and fully integrated the 1pps output of the GPS receiver).
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