Arduino Fio 1.8V voltage supply

Dear All, I would like to supply Arduino Fio with 1.8V instead of 3V. I simply tried to supply 1.8V without success; after read ATMega328 datasheet I saw that: Speed Grade: ̶ 0 - 4MHz@1.8 - 5.5V, 0 - 10MHz@2.7 - 5.5.V, 0 - 20MHz @ 4.5 - 5.5V So I think if I would like to use 1.8V I should substitute oscillator 8MHz with 4Mhz. Some questions about above: 1) Is it right my idea? 2) If I changed oscillator value, how can I redefine the oscillator value into Arduino firmware?

Thanks for your answer, bye

1) Is it right my idea?

Yes.

2) If I changed oscillator value, how can I redefine the oscillator value into Arduino firmware?

I don't know, but if you are not doing anything involving time it won't matter.

I assume there is a variable in the compiler or linker so the timing functions are appropriately scaled for the actual clock.

You won't be able to use the regular IDE/bootloader to download your program (or the serial monitor) if the clock frequency is "wrong".

Or if you are using millis() or micros() you can write a function that multiplies the returned values by two.

New boards.txt entry is needed. This will need to set F_CPU to 4000000L to get the speed right.

Also, you will need to change the fuses to disable BOD, in addition to replacing the crystal (alternately, you could leave the crystal, but set the fuses to divide it by 8, then change the clock prescaler to 2 at the start of the sketch). Actually, you may find that it just works at 8mhz with BOD disabled... (though this is out of spec, ofc)

The Fio is all about XBee isn't it though? Does the XBee stuff you connect to it work at 1.8v?

Thanks for your replies. I would like to heart rate monitor chip Maxim MAX30100. It works at 1.8V power supply, that's why I wish to use 1.8V for Ardunio Fio. MAX30100 will connect to Arduino by I2C. An alternative could be to supply Arduino with 3.3V and MAX30100 with 1.8V: in this way do you think that it could work or I could damage the input line of MAX30100. Thanks Best regards

Hi ,I am a chip designer. I am new to the arduino world recently. And I am also trying to put together the design for max30100.

From the datasheet of max30100 ,it requires 2 power supply ,~3.3v for LED and ~1.8v for IO and control. So I am preparing to use the 3.3v supply from the "Arduino" board (actually I will use cc3200 development board instead) and use one of its(cc3200) pin to provide 1.8V to max30100. Basically the datasheet says it can not tolerate vdd above 2.2V or it would fail. Also I bought a LDO chip which can do 3.3v to 1.8v in case I need to .

And for the SDA/SCL/INT_bar ,they can also take only 1.8v ,so I bought a voltage level converter board to do the work. So it can help the logic pins talk to the CC3200(or Arduino) GPIO pins.

For the rest is the coding part that I am about to start.

Welcome to write message to me if you have hardware related issues for discussion.

Good luck.

Randy

(P.S. I do not think you can change the clock to apply 1.8v to Arduino ,it won't work like this generally with the electronics "chips" ,so that is the general need to use LDO or DCDC circuit for setting up voltage supply)

We are using MAX30100 with CC3200 texas instrument ARM kit. The power supply to the ARM kit is 3.3 volts and to MAX30100 is 3.3volts for Ir sensors and 1.8 volts for the IC. We have connected ARM with MAX using a level translator from MAXIM. We use seperate power supply for 1.8 and 3.3. MAX 30100 IC failed often and we donot know the reason?