Re: [avr-chat] Using the /Reset line for I/O on a Tiny85

[Joerg Wunsch]

"Alex Shepherd" <address@hidden> wrote:

> My real question is how easy is it in practice to configure the
> Dragon or JTAG MkII to reconfigure the /Reset pin all the time using
> HV ICSP so I can develop/debug the code while the /Reset line is
> used for I/O as well as debugWire?

The JTAG ICE mkII cannot perform HV programming, only the Dragon and
the STK500 offer that feature.  Naturally, using the pin for debugWire
and for IO is mutually exclusive.  HVSP is not designed as an
in-system programming protocol, but as long as your remaining
circuitry does not interfere with the signals used for HVSP (including
the +12 V pulse on /RESET), I don't see why it couldn't work.
Obviously, an alternative option would be to place the controller in a
socket for development work, and then take it out into the programmer
socket for HV programming.

Yet another option is to implement a bootloader.

> I could only use the /Reset pin for an infrequent use that I can
> live without while developing and then re-enable when I'm done if
> that makes a difference.

Either that, or use a chip with more pins for development, and then
downscale to the ATtiny85 once the application is basically debugged.

-- 
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)