Need help to use microseconds delay outsite void loop

Using Arduino Project Guidance
#1

Hi!

Need help to get my delay in milliseconds to microseconds, have tried google this problem but I am not much of an programmer and haven´t found anything that could help me.

My problem is that I want to use an delay outside the void loop in microseconds instead of milli. This is my code:

#include <util/delay.h>
//-----------------------------------------------
int const valve_in = 8;
int const valve_ut = 9;
int const matgaffel = 3;

volatile byte matskiva_plats=1;
volatile int pressure=55;
volatile int unsigned time = 30 ;
byte desiredmax = 70;
byte desiredmin = 55;

int start=0;

unsigned long timeold = 0;

//------------------------------- ----------------
void setup()
{
Serial.begin(9600);

pinMode(valve_in,OUTPUT);
pinMode(valve_ut,OUTPUT);
pinMode(matgaffel,INPUT);
attachInterrupt(1, valve_ut_fun, RISING);
pinMode(A0,INPUT);
}
//-----------------------------------------------
void loop()
{
if(matskiva_plats==1)
attachInterrupt(1, valve_in_fun, RISING);
else
attachInterrupt(1, valve_ut_fun, FALLING);

}
//-----------------------------------------------
void valve_in_fun()
{
Serial.println(pressure, DEC);

if(start>20)
{
if(pressure<desiredmin)
time++;
else if(pressure>desiredmax)
time–;
}
else
start++;

digitalWrite(valve_ut, LOW);
digitalWrite(valve_in, HIGH);

delay_ms(time);

digitalWrite(valve_in, LOW);

attachInterrupt(1, fix, CHANGE);
matskiva_plats=0;
}
//-----------------------------------------------
void valve_ut_fun()
{
pressure=analogRead(A0);
digitalWrite(valve_ut, HIGH);

attachInterrupt(1, fix, CHANGE);
matskiva_plats=1;
}
//-----------------------------------------------
void delay_ms(unsigned int time)
{
while (time–)
_delay_ms(1);
}
//-----------------------------------------------
void fix()
{
delay_ms(1);
}

//-----------------------------------------------

What my program does is controlling two inlets/ outlets for an air engine depending on the pressure when the piston reaches its lowest point. But when putting this to practical use the engine/ car hacks forward because changing 1ms makes to much differense in air inlet.

Pls help, thanks

#2

Have you tried the function delayMicroseconds()? The value you pass is an "unsigned long".

#3

What I have found is that I can´t have delay function in the attachinterupt, that´s why I have delay_ms, I wonder if there is something similar to delay_ms but for microseconds, Like can I just replace ms with us and it will work?

#4

The delayMicroseconds() function will work in an ISR.

Oops, the input value is an unsigned int, not unsigned long. The longest usable delay is about 16000 microseconds.

#5

So you are saying that I could rewrite my code as follow aslong as I dont exceed time = 16000?

#include <util/delay.h>
//-----------------------------------------------
int const valve_in = 8;
int const valve_ut = 9;
int const matgaffel = 3;

volatile byte matskiva_plats=1;
volatile int pressure=55;
volatile int unsigned time = 30 ;
byte desiredmax = 70;
byte desiredmin = 55;

int start=0;

unsigned long timeold = 0;

//------------------------------- ----------------
void setup()
{
Serial.begin(9600);

pinMode(valve_in,OUTPUT);
pinMode(valve_ut,OUTPUT);
pinMode(matgaffel,INPUT);
attachInterrupt(1, valve_ut_fun, RISING);
pinMode(A0,INPUT);
}
//-----------------------------------------------
void loop()
{
if(matskiva_plats==1)
attachInterrupt(1, valve_in_fun, RISING);
else
attachInterrupt(1, valve_ut_fun, FALLING);

}
//-----------------------------------------------
void valve_in_fun()
{
Serial.println(pressure, DEC);

if(start>20)
{
if(pressure<desiredmin)
time++;
else if(pressure>desiredmax)
time–;
}
else
start++;

digitalWrite(valve_ut, LOW);
digitalWrite(valve_in, HIGH);

delayMicroseconds(time);

digitalWrite(valve_in, LOW);

attachInterrupt(1, fix, CHANGE); //
matskiva_plats=0;
}
//-----------------------------------------------
void valve_ut_fun()
{
pressure=analogRead(A0);
digitalWrite(valve_ut, HIGH);

attachInterrupt(1, fix, CHANGE); //
matskiva_plats=1;
}
//-----------------------------------------------
void fix()
{
delayMicroseconds(1);
}

//-----------------------------------------------

Kind regards

#6

If you put a delay much more than 900 microseconds in an ISR you will start to lose timer interrupts and the millis() function will lose time.

I’m not sure I follow the logic. I don’t see how the delay in the ‘fix’ ISR does anything useful.

You don’t need “#include <util/delay.h>” anymore.

You shouldn’t use .print() or .println() in an ISR. If the buffer is full your code will lock: .print() will be waiting for the buffer to empty but since the interrupts are disabled the buffer can’t empty.

#7

It seems to me that switching interrupt handlers repeatedly as you're doing is not a good strategy, and imo it would be clearer and simpler just to write an interrupt handler that implemented the logic you need, using state variables if necessary. Additionally, I can't see the purpose of fix(). Conventional wisdom is that interrupts should do as little as possible and especially not do any delays. In this case a short delay is all it does - how is that useful?

#8