[minima] Re: About running ATmega328 at 3v3
- From: farhanbox@xxxxxxxxx
- To: minima@xxxxxxxxxxxxx
- Date: Thu, 6 Feb 2014 14:00:10 +0000
Paolo,
I have tried to use parts that are universally available. The commonly
available parts are the 5v 328P chips.
I have used the Si570 with the 3.3v pullups in several projects without any
problems. They continue to putter along without a hitch.
- f
Sent from BlackBerry® on Airtel
-----Original Message-----
From: Paolo Cravero <paolo.cravero@xxxxxxxxx>
Sender: minima-bounce@xxxxxxxxxxxxx
Date: Thu, 6 Feb 2014 14:10:41
To: <minima@xxxxxxxxxxxxx>
Reply-To: minima@xxxxxxxxxxxxx
Subject: [minima] About running ATmega328 at 3v3
Hello.
I have been playing with bare AVR ATmega chips in the past (no Arduino
bootloader) and gave a thought about running it at 3v3 in this project.
While clocking at 8 MHz most probably wouldn't be a performance issue, the
following has to be taken in consideration.
The pre-loaded Arduino bootloader has been designed to run at 16 MHz clock.
This includes timings for the serial port. While halving the clock should
result in half baud rate, "you'll need to change the serial.download_rate
in your preferences file <http://arduino.cc/en/Hacking/Preferences> to
9600." (quoted from
http://arduino.cc/en/Hacking/Bootloader?from=Main.Bootloader). Also the
sketch/programm will need to be aware of the new clock speed. Another
option would be to program the ATmega outboard at 16 MHz/5V and then move
the chip in MINIMA (not too practical either).
AVR chips have electronic "fuses". See them as an invisible set of
DIP-switches. Fuses control few things in the chip, including the type of
clock to be used. 8 MHz is at the border betweek two XTAL ranges, and an
experiment needs to be done in order to confirm that default Arduino/chip
reseller settings are fine. As far as I know Arduino IDE does not touch
fuses.
As a sidenote, I was thinking whether the serial board is really needed.
Nowadays it is hard to find a computer with true RS232, while a
USB-to-TTLserial costs 3-4-5 USD shiipped, and is universal.
Paolo IK1ZYW
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