AVR-Chat

On Sep 2, 2010, at 9:36 PM, Jim Wagner wrote:

> That argues for an external pullup on the SS line to make sure it is  
> not asserted during reset.

That is precisely what I started thinking about as I wrote that.  The only system I designed where it might have been an issue had another way to inhibit outputs off the SPI so I haven't had to deal with it yet.

> 
> Jim Wagner
> Oregon Research Electronics
> 
> On Sep 2, 2010, at 9:20 PM, Clark Martin wrote:
> 
>> 
>> 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"
>> 
>> 
>> 
> 
> 
> 
> [Non-text portions of this message have been removed]
> 
> 
> 
> ------------------------------------
> 
> Yahoo! Groups Links
> 
> 
> 

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

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