Operating atmega328 at 3.3volts, rather than 5v ?

[u]http://www.atmel.com/dyn/products/product_card.asp?PN=ATmega328P[/u]

Atmega 328 Description: Key Parameters: picoPower technology AVR Microcontroller. 32KB self-programming Flash Program Memory, 2KB SRAM, 1024 Bytes EEPROM, 8 Channel 10-bit A/D-converter(TQFP/MLF). debugWIRE On-chip Debug System. Up to 20 MIPS throughput at 20 MHz. Operating Voltage: 1,8V - 5.5V

Many arduino boards operate at 5. volts. Since some of the newer cards operate at 3.3v, and atmel states that the operating voltage of an atmega 328 lies between 1.8v - 5.5v, would it be possible to use an atmega328, with arduino bootloader, at 3.3v? I could put a board together, maybe an RBBB, and use a 3.3v regulator instead of a 5v reg.

Doing so would eliminate the need for voltage dividers when connecting an arduino to devices that need to be operated at 3.3v. (devices such as SD cards)

Or should I just go ahead and try, And see what will fry? ;D

PO'T

I've powered a no-bootloader 328 and 168 from two and three AA batteries. I believe the Arduino fuse settings enable the Brown Out Detector for just over 4 volts. You may not be able to use 3.3V unless you can change the fuses.

Check the ATmega328p specs for the maximum clock speed for a given voltage... At 1.8V you can clock upto 4MHz, at 2.7V upto 10MHz and 4.5V upto 20MHz.

You also need to check the brown-out detection is setup correctly - you may get away with using one of the 3.3V board settings (Mini, Pro Mini) to get the Arduino IDE to setup the brownout settings right, but I'm not sure - failing that you can create your own board settings (delve in the hardware/boards.txt file - but back it up first just in case)

Okay, that doesn't sound like such a good idea. I don't think I'll try it. Sounds like one would have to relearn WinAVR, fuses, etc. Bah. ::)

PO'T

No its not hard, just try one of the 3.3V board settings - or look in hardware/boards.txt to see how they are defined. 3.3 volts is so common these days for sensors it makes a lot of sense (unless you need the MIPs that 5V gives you).

Since SD cards operate at 3.3v, I would like to be able to connect an arduino directly to a card without using a voltage divider. I'm not sure what MIPS stands for. Frequency of operation? Something to do with baud rate?

I know that there are 3.3v arduino boards for sale, now. (SparkFun has an arduino w/atmega328, which operates at 3.3v)

I have the makins' for an RBBB from: ([u]http://www.moderndevice.com/products/rbbb-pcb[/u]), minus the atmega168 or 328. I am also able to burn an arduino bootloader on one, but I am not sure if I could just use a 3.3v regulator or a five volter.

PO'T

You do know the Duemilanove offers a 3.3V power line. So sending power to an SD card wouldn’t be an issue. The board doesn’t run off of the 3.3V but the voltage regulator on the board was made to off 3.3V to support ad-dons that needed 3.3V rather then 5V.

digimike Re: Operating atmega328 at 3.3volts, rather than 5v ? Reply #6 - Yesterday at 22:36:35 | You do know the Duemilanove offers a 3.3V power line. So sending power to an SD card wouldn't be an issue. The board doesn't run off of the 3.3V but the voltage regulator on the board was made to off 3.3V to support ad-dons that needed 3.3V rather then 5V.

True, but 5v outputs from the arduino to an SD card need to be reduced as well. (arduino pins 10, 11, and 13).

I guess a voltage divider isn't such a problem, such as the one shown in this thread: u[/u]

I also realized (just) that an arduino operating at 3.3v, would also need a programmer for that voltage. :-?

PO'T

You just need to reduce the clock frequency to apx 12MHz or lower. Change the CPU frequency setting in the Makefile and add a new configuration to boards.txt Information on the bootloader changes I do is at http://wiblocks.luciani.org/docs/app-notes/bootloader.html I will be adding the information on the boards.txt updates in the next few weeks.

All of my board run at 3.3V / 12MHz (see http://www.wiblocks.com ) In the next few weeks I am hoping to release my PICO1-TR 2.1" x 0.975" ('328, TH components) adjustable regulator -- can be trimmed to voltages from 3.3V to 5V by changing one resistor.

(* jcl *)


www: http://www.wiblocks.com twitter: http://twitter.com/wiblocks blog: http://luciani.org

Standard Duemilanove running at 3.03 volts : http://www.youtube.com/watch?v=g1K-hbsyfAU admittedly its only blink.