hi!!
i'm beginner here 
, can anyone tell me about how to generate square pulses having freq range 1hz-100hz & am working on stimulator for human body & for this i want to generate using potentiometer, also having variable amplitude.
your help will be very helpful for me.
Thanks in advace
Blink without delay.
Use micros()
Other than a learning experience, a terrible waste of a duino.....
How about a 555, some resistors, a cap, and some simple math?
Generating the squarewave is pretty easy using blink without delay style programming. We'll use an analog input to select the frequency.
int analogIn; // hold pot value
byte squareOut = 2; // output pin, PORTD bit 2 on an Uno
unsigned long halfPeriod; // 32 bit data to hold frequency = halfPeriod x 2
unsigned long currentMillis; // 32 bit value for time comparison
unsigned long elapsedMillis; Â // 32 bit value for time comparison
unsigned long previousMillis; // 32 bit value for time comparison
void setup(){
pinMode (squareOut, OUTPUT);
// Serial.begin(115200); // send messages to serial monitor for debugging
}
void loop(){
// read the pot, which has one outer leg wired to +5, the other to Gnd, the wiper to A0
analogIn = analogRead(A0); Â // number from 0 to 1023
// 100 Hz = 10mS period, change level every 5mS, or 5,000uS
// 1Hz = 1000mS period, change level every 500mS, or 500,000uS
// everything else is in between
if (analogIn <=10){
analogIn = 5; // max speed
}
if (analogIn >=1000){
halfPeriod = 500; // min speed
}
if ( (analogIn >10) & analogIn<1000){
halfPeriod = analogIn/2; // everything else
}
// see if time to change output level
currentMillis = millis(); // capture the current 'time'
elapsedMillis = currentMillis - previousMillis; // how much 'time' has passed since last capture
if (elapsedMillis >= halfPeriod){ // enough has passed: do something
previousMillis = previousMillis + halfPeriod; // set up for next level change
PIND = 0b00000100; // flips D2 from Hi to Lo, or Lo to Hi
}
// do other stuff while waiting for next half period
} // end loop
For amplitude variation:
Connect D2 to one leg of a 1k or 5K pot, other leg to Gnd, wiper is the variable level output.
Thank you soo much 
Let me try to understand it and practically implement this then if i'll have any query i'll ask you again.
thanks again for this great help:)
I didn't compile that, but it should be fairly close.
i'll fix those minor issues thanks
@
CrossRoads
I want to ask, can i use any value of potentiometer for frequency selection let say 1k, does it matter on values in code?
No, does not matter.
Lower value will just use more current.
5V/1000 ohm = 5mA.
Voltage level at analog input will be the same.
Thank You soo much for your guidance
You're welcome.
@
CrossRoads
Hi!!
one thing more i want to ask can i used the above code output for mega on digital pin 45(PORT D bit 2) ?
Sure.