AVR-Chat

On Sep 2, 2010, at 9:02 PM, Jim Wagner wrote:

> Most of the ATtinys that that have debugging have DebugWire which uses  
> the reset pin, only. Check the processor you are interested in for  
> DebugWire. If it does not have it, then no debugging on that chip.
> 
> You might need a way to isolate the other lines during operation if  
> you need to actively use one of those lines. I seem to recall folks  
> using a series resistor between the programming connector and the  
> micro, in that case.

On the ATMegas I use a 1K ohm resistor between the shift register and the MISO pin on the chip (and the pin to the programmer).  AFAIK the Tinys should work the same way.  None of the other pins need any isolation since only the MISO is an input to the chip.  You do have to watch out for the serial stream affecting the SPI device(s) but that isn't likely since SS shouldn't be driven low (although it might float low since it will be hi impedance until the SPI is initialized).

> 
> Jim
> 
> On Sep 2, 2010, at 8:48 PM, Philippe Habib wrote:
> 
>> I'm considering an ATTiny part but I'm not totally clear on the
>> programming and if source level debug is supported. My reason for the
>> ATTiny is the physical size I can have is very constrained.
>> 
>> The programming data line is also the I2C data line. Does that mean
>> no I2C if I want in circuit programming?
>> 
>> Is source level debugging possible on the part?
>> 
>> I'm guessing that I can't have source level debug and I2C at the same
>> time since they share a pin.

Clark Martin
Redwood City, CA, USA
Macintosh / Internet Consulting

"I'm a designated driver on the Information Super Highway"