How to use PulseIn() with small voltage up time reading ?!!

i want to use pulsein function to read the voltage up time note volt is variable between 1.2 : 3 :( :( :( :(


i want to use pulsein function to read the voltage up time

The pulseIn() function times how long between a pin going LOW (0V) and it going HIGH (5V) again, or between it going HIGH and it going LOW.

It is NOT useful for analog voltages, since it doesn't even know that analog pins exist.

yup, i know that so i want to edit the function body to read anloginput but need help wiz that :D

So, what have you got? (Remember that analogRead takes around 100us)

#include "wiring_private.h"
#include "pins_arduino.h"

/* Measures the length (in microseconds) of a pulse on the pin; state is HIGH
* or LOW, the type of pulse to measure.  Works on pulses from 2-3 microseconds
* to 3 minutes in length, but must be called at least a few dozen microseconds
* before the start of the pulse. */
unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout)
 // cache the port and bit of the pin in order to speed up the
 // pulse width measuring loop and achieve finer resolution.  calling
 // digitalRead() instead yields much coarser resolution.
 uint8_t bit = analogPinToBitMask(pin);
 uint8_t port = analogPinToPort(pin);
 uint8_t stateMask = (state ? bit : 0);
 unsigned long width = 0; // keep initialization out of time critical area
 // convert the timeout from microseconds to a number of times through
 // the initial loop; it takes 16 clock cycles per iteration.
 unsigned long numloops = 0;
 unsigned long maxloops = microsecondsToClockCycles(timeout) / 16;
 // wait for any previous pulse to end
 while ((*portInputRegister(port) & bit) == stateMask)
   if (numloops++ == maxloops)
     return 0;
 // wait for the pulse to start
 while ((*portInputRegister(port) & bit) != stateMask)
   if (numloops++ == maxloops)
     return 0;
 // wait for the pulse to stop
 while ((*portInputRegister(port) & bit) == stateMask) {
   if (numloops++ == maxloops)
     return 0;

 // convert the reading to microseconds. The loop has been determined
 // to be 20 clock cycles long and have about 16 clocks between the edge
 // and the start of the loop. There will be some error introduced by
 // the interrupt handlers.
 return clockCyclesToMicroseconds(width * 21 + 16); 


And how’s that working for you?

error at " uint8_t bit = analogPinToBitMask(pin); "

I’ve used a saturating preamp to a digital input for something similar - see the enclosed.

It works from about 50mV p-p upwards.


revpre.pdf (18 KB)