AVR-Chat

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.

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.

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.
>
> 



[Non-text portions of this message have been removed]

Hi Philippe,
 
You need to check the datasheet for the intended devices you want to use.
Some of the later Tiny devices have debug wire to allow in circuit software
debugging. This uses the reset line so no IO lines need be used up.
 
As for sharing the I2C with programming, you can most often get away with
fitting a resistor in series with the I2C device to allow the lines to be
used for programming. 
 
As you will only be using the programming port for production, this won't be
an issue for you as during development the programming would be done via the
DebugWire interface so your IO pins will be fully available during source
level debugging.
 
Dave.

From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of Philippe Habib
Sent: 03 September 2010 10:48
To: AVR-Chat@yahoogroups.com
Subject: [AVR-Chat] ATTiny programming and debug
 
  
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.

No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 9.0.851 / Virus Database: 271.1.1/3107 - Release Date: 09/03/10
01:50:00


[Non-text portions of this message have been removed]

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"

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

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]

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"