arduino mega != 650khz

Projects Programming
1

I couldn't generate 650khz with arduino mega

using write High,
write Low,

The highest frequency was 47khz,
even with arduino Uno,
pls help

2

Try a different method:

byte PINx = XX; // where XX is whatever pin PORT D bit 2 is for example
void setup(){
pinMode (PINx, OUTPUT);
}
void loop (){
PIND = 0b0000100; // toggle PORT D bit 2 by writing a 1 to input register
}

650 KHz = 1.538uS, or 24.6 clocks not a lot of time to do much else.
You may also want to look into using a PWM output for this.

3

Thanks I ll try that too

4

It seems all my efort prove abortive, I couldn't generate the 650khz,
I think I need detailed help thanks

5

What frequency do you see with the PIND code?

6

I couldn't count any number of cycles on the PIND, maybe I couldn't fit in that sketch
I need more detail

7

In fact I do not generate frequency with PIND library,
I always generate square wave frequency by,
digitalWrite pin High and Low,
that's all
I don't know about PIND

8

Then your getting top speed for software only.

Anything more? if yes then

POST YOUR CODE!!!!!

Mark

9

If you put an infinite loop inside the loop function, you'll cut out all the serial "event" stuff in main.

10

Yes I generated 10khz with the delayMicrosecond (100),
When I have to make 650khz, I didn't delay it at all, but my top speed
Was only 47khz

11

ulobab:
When I have to make 650khz...

Precisely 650 kHz? If yes then you are not going to get it with a typical Arduino board. You can have...

16000000/(21(11+1)) = 666666.666667 Hz

...or you can have...

16000000/(21(12+1)) = 615384.615385 Hz

Which does not account for any inaccuracy in the resonator / crystal.

Edit: corrected the frequency possibilities

12

code CODE CODE CODE CODE CODE

Mark

13

Not exactly 650khz but anything close, 640khz is ok , as well as 660khz ,
how can I generate that with my Uno, I need help with complete sketch
thanks

14

ulobab:
how can I generate that with my Uno

Configure a timer (timer 1 or timer 2) to run in CTC mode with a prescaler of 1 and an appropriate TOP value. Don't forget to change the pin to an output.