Re: [avr-chat] Crystals (was ATmega32 @ 16MHz : fuse bits ??)

[Joerg Wunsch]

"Graham Davies" <address@hidden> wrote:

>> Q2: since there are Mk1 clones, are there mk2 clones ?

> I don't know of any.  I don't think Atmel have released any
> information about DebugWIRE and I haven't come across any reverse
> engineering of the Atmel Mark II.

Well, the mkI has been reverse-engineered (the hardware, the software
not that much).  But then, the mkI is internally much simpler than the
mkII device (one ATmega16 plus stuff, compared to a couple of
ATmega128 plus stuff, each running their own firmware).  You can plug
an mkI clone together on an STK500 used as a breadboard, and connect
the `squid' cable (the one with the colored wires) to it as the JTAG
interface.  All you need in addition is a 7-dot-something crystal.

> If so, why not restrict
> yourself to AVRs with JTAG interfaces?

AFICT, all the newer AVRs won't be supported by the mkI JTAG ICE
anymore (regardless of whether you're going to use dW or JTAG).

>> [the internal RC oscillator] is not accurate ...

> I think you are right to insist on a crystal if you're using the
> UART.

For UART communication, the precision of the internal RC oscillator is
sufficient.  The only tricky thing is if you want to use it on Vcc
other than 5 V, because the factory-shipped calibration values are all
provided for 5 V only.  For other voltages, you've got to find your
own calibration method.

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

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