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[Reply #15 on:]

There is a difference between being a hobby product and being a toy.

The only thing different between a man and a boy is the size (price) of their toys.

Now, who's belittling the Arduino?

No at all
Tiny = baby
I am very new to the Arduino line of micro controllers and I know that tiny is in one of their board names.  I did not want someone to think I was talking about a specific board.

[Reply #16 on:]

I used this opportunity to check the digital...Fast routines.
This here is around the limit

Code:

#define ledPin 13
 Timer1.initialize(12);         // called every 12 us

 Timer1.attachInterrupt(callback);
 pinMode(ledPin, OUTPUT);

 int i;
 int pWidth = 0;
 void callback() {
   digitalWriteFast(ledPin, HIGH);   // set the LED on
   i = pWidth;
   while (i>0)  --i;
   pWidth +=4; //delay is 0, 4, 8, or 12 loops = 1.5, 3, 4.5, or 6us
   if(pWidth>12) pWidth=0;
   digitalWriteFast(ledPin, LOW);  
}

This uses nearly half of the processor time. It was not possible to make much faster interrupts; around those 83kHz seems to be the limits.
Pulses generated are 1.5, 3, 4.5, and 6us long, a much better fine tuning is possible here; my delay code is a little bit clumsy...

Remember that the pins for digital...Fast have to be constants!!

[Reply #17 on:]

Thank you for the code.  I have printed it out and will look over it.  There are a few things I don't understand yet.

Is there a way or a function to output a byte to port D, pins 0-7?  It seems that the Duemilanove only manipulates bits.

[Reply #18 on:]

Manipulation of "bits only" is a feature of the Arduino HAL. You can of course use the register layer below, as with any AVR chip!

----

You have to change my code in at least two ways
- the pulse must be output to four different lines during four succeding interrupts.
- each fourth interrupt must be delayed for 2 us to make exact 20kHz.

However it should be possible to change the timer initialization (prescaler) to have 12.5us interrupts

[Reply #19 on:]

It seems that the Duemilanove only manipulates bits.

No see:-

http://www.arduino.cc/en/Reference/PortManipulation

[Reply #20 on:]

Mike,

Thank you for pointing that out to me.  How about this, Is there a windows based cross asembler that will work with the Duemilanove?

[Reply #21 on:]

A cross-assembler in addition to the C++ compiler?

[Reply #22 on:]

Stand-alone would probably be better as it is intimidating to most people.  I have experience with 6502, 6809, 68705, 6811, and 8088.  You have better access and control of registers and memory and it is the ultimate in execution speed.