Re: [avr-gcc-list] newbie trying to get at90s8515 to work on breadboard

[Chris Donovan]

On Sat, 8 Jan 2005 11:34:49 +0000
Richard Urwin <address@hidden> wrote:

> >  I am trying to get an at90s8515 to work on a breadboard.  Basically
> > I have an atstk500 and the chip(at90s8515) works just fine on that
> > board but when I move it to a breadboard I can't get it to work
> > correctly. The C code for it is below.  portb0-7 are being used to
> > activate/de-activate the LED's on the stk500 board, and they work
> > just fine when the chip is inserted into the stk500.
> >
> >  I have connected pin 40(vcc) to the +9V supply(tried 5-9V) with
> >  misc
> > resistance to lower it to 5V.  When I connect up portb0 on the
> > breadboard to the +LED terminal, it does not work as expected.  It
> > just keeps the LED on all the time instead of blinking like it
> > should. If I connect pin20 to the  the 9V it doesn't activate the
> > LED at all, and the LED just stays off.
> 
> It would be worth checking that the LED still lights when you connect
> it to portb0. Feeding voltage directly to an LED will kill it in 
> milliseconds. It's also worth putting the 8515 back into the STK500
> and checking that it still works too.

Yes it does work when I put it back on the stk500.  The LED does work as
I am reducing the voltage via a 410ohm resistor.  I am trying to get to
a target voltage of roughly 5V.  I think that is what I need since the
VCC in the spec sheet says 5V I am not sure of the amperes though but I
am guessing .01?

> >  I really haven't the slightest clue of why it isn't working but I
> >  am
> > thinking perhaps I need to connect more pins on the breadboard to
> > more things?
> 
> Could you tell us the full connections you are making to the
> processor? You don't mention 0V or RESET. These are required, as is
> XTAL1 and XTAL2 if you haven't set the fuses to use an internal clock.

I don't have either XTAL1|2 connected to anything at the moment.

Ok so basically I have the following:

+9V --> 410ohm --> pin40(VCC)
pin20(GND) --> -9V
pin1(PB0) --> 40ohm --> LED(2V)

When I connect the GND the LED goes out but when disconnected the LED is
on, and I don't exactly understand why as yet.

> If the same chip works in the STK500, and the clock speeds are 
> comparable, then the software is working well enough at the moment,
> and you don't want to change it.

I am trying to use the internal clock(oscillator?), but from what I have
read so far from a couple of emails sent to me already I will need to
buy a crystal(4Mhz?).  I might have to adjust the delay because of the
different speeds.  I think the internal clock runs at 3.68 roughly.  Do
I just need a crystal or a full oscillator?  Which one is more
efficient?  I saw on page 6 of the spec sheet that it can be done either
way but I don't have either the oscillator or the crystal with 2 caps,
so what is a good way to go?  I was thinking of just getting an
oscillator(4 pin?) and using that instead of getting the crystal with 2
caps.

I hope this is the appropriate mailing list for such queries and if not
what is an appropriate list to send these queries to?  As I am sure this
email shows I am quite new to all of this electrical stuff (:

Thanks Again,

Chris-