Re: [avr-chat] New Programmer, Small Program, F_CPU for Atmega644

[Marge Coahran]

You mentioned before that you intend to blink an LED with this, right?
You can connect the LED portion of your circuit as either of the 
following, and the resistor can go on either side of the LED. (The long 
leg of your LED should be toward power, or away from ground.)

  AVR output pin -> LED -> resistor -> ground

  AVR output pin -> LED -> resistor -> power (VCC)

You can expect the LED to drop about 1.7V, so if you are supplying 5V, you 
have 3.3V to be dropped by the resistor. Ohm's law (which applies to 
resistors, but not everything) tells us that V = I * R. You want a current 
of about 20mA to light the LED. Thus, use a resistor with
R = 3.3/.02 = 165 Ohms.  These numbers are rough enough that you should 
be fine with any similar resistor you happen to have.

Forgive me if this is more detail than you wanted.
-Marge

On Sun, 23 Mar 2008, Robert L Cochran wrote:

> Joerg Wunsch wrote:
> > Since it's small enough to post, here's the hex file when compiling
> > for an ATmega644:
> >
> > :100000000C9438000C9455000C9455000C94550039
> > :100010000C9455000C9455000C9455000C9455000C
> > :100020000C9455000C9455000C9455000C945500FC
> > :100030000C9455000C9455000C9455000C945700EA
> > :100040000C9455000C9455000C9455000C945500DC
> > :100050000C9455000C9455000C9455000C945500CC
> > :100060000C9455000C9455000C9455000C945500BC
> > :1000700011241FBECFEFD0E1DEBFCDBF11E0A0E065
> > :10008000B1E0ECE6F1E002C005900D92A030B107BE
> > :10009000D9F711E0A0E0B1E001C01D92A330B10793
> > :1000A000E1F70E94AB000C94B5000C9400001F9285
> > :1000B0000F920FB60F9211242F933F938F9380913D
> > :1000C0000001882379F420910101309102012F5F12
> > :1000D0003F4F309302012093010183E02F3F380707
> > :1000E000D9F417C0813029F020910101309102012B
> > :1000F00013C0209101013091020121503040309312
> > :100100000201209301012115310531F41092000103
> > :1001100003C081E080930001309389002093880020
> > :100120008F913F912F910F900FBE0F901F901895B8
> > :1001300083E880938000E1E8F0E080818160808343
> > :10014000109289001092880080E28AB981E0809341
> > :100150006F00789408950E94980083B7816083BFF0
> > :0C016000889583B78E7F83BFF8CFFFCF58
> > :00000001FF
> Thanks Joerg for posting this. I have a breadboard circuit ready to test
> with this hex file. I was planning to use a lithium polymer battery that
> pumps out 12v at 1300 mA. I connected that to a power supply board which
> will give me 5v output and 1100 mA current. That is way too much current
> for the Atmega644, isn't it? The absolute maximum ratings on the
> datasheet list 200 mA as the maximum on VCC and GND. Of the "wall wart"
> power supplies I am using, I have one that puts out 5v and I've measured
> 350 mA current. So I need to cut down the current for the AtMega 644
> device, right? I can reduce the current with resistors? I will Google to
> learn how to do this.
>
> Thanks
>
> Bob Cochran
>
>
>
>
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