AVR-Chat

It  should also be a circuit that does not care about the
signals during programming.

If it is an SPI peripheral, make sure the Select line is
pulled high with an external resistor because all the other
processor pins are tri-stated with no internal pullup while
ISP is running.

Jim


On Fri, 02 Nov 2007 06:32:39 +1100
 John Samperi <samperi@ampertronics.com.au> wrote:
> At 05:45 AM 2/11/2007, you wrote:
> >What can you
> >"hang off" of the SPI lines to allow the chip to be
> programmed
> 
> Pretty much anything above 1K, but make it as high as
> possible.
> 
> 
> Regards
> 
> John Samperi
> 
> ********************************************************
> Ampertronics Pty. Ltd.
> 11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
> Tel. (02) 9674-6495       Fax (02) 9674-8745
> Email: john@ampertronics.com.au
> Website  http://www.ampertronics.com.au
> *Electronic Design * Custom Products * Contract Assembly
> ********************************************************
> 

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Hi Folks,

I'm planning on using the ATtiny13 chip because of cost and space
constraints.  I need 2 outputs and 1 A/D input to read the battery
voltage (3V coin cell Lithium) every so often to signal to the end
user that the battery should be changed.  

The chip has 6 I/O pins but one needs to be saved for the RESET pin,
and 3 are used for the SPI lines to program the chip.  I've been using
the Dragon to program/debug other designs so I'd like to keep using that.

So now to my question -(sorry for being long winded) - What can you
"hang off" of the SPI lines to allow the chip to be programmed via the
SPI lines but then after the program starts change the pins to an
output and an A/D input?  I'd like to use one of the pins as an output
to drive a resistor divider with the middle connected to one of the
A/D inputs.

Thanks again,

Richard Cooke

At 05:45 AM 2/11/2007, you wrote:
>What can you
>"hang off" of the SPI lines to allow the chip to be programmed

Pretty much anything above 1K, but make it as high as possible.


Regards

John Samperi

********************************************************
Ampertronics Pty. Ltd.
11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
Tel. (02) 9674-6495       Fax (02) 9674-8745
Email: john@ampertronics.com.au
Website  http://www.ampertronics.com.au
*Electronic Design * Custom Products * Contract Assembly
********************************************************

--- In AVR-Chat@yahoogroups.com, "Richard Cooke" <rcooke@...> wrote:

> ... What can you "hang off" of the
> SPI lines to allow the chip to be
> programmed ...

Not answering your question at all ... if you're not totally committed 
to the ATtiny13, consider the pin-compatible ATtiny25, ATtiny45 / 
ATtiny85 and program them using just the reset pin using debugWIRE.

Graham.

At 11:51 AM 2/11/2007, you wrote:
>program them using just the reset pin using debugWIRE.

...except the fuses and lock bits of course as DW does not do them.



Regards

John Samperi

********************************************************
Ampertronics Pty. Ltd.
11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
Tel. (02) 9674-6495       Fax (02) 9674-8745
Email: john@ampertronics.com.au
Website  http://www.ampertronics.com.au
*Electronic Design * Custom Products * Contract Assembly
********************************************************