If we want to use arduino with 3V, could we just change the chip and the clock of the Serial version or we have to consider other things?
Is there an example of an Arduino built with the ATMEGA8L ?
Hi gll!
The IC called "7805" in the board make a 5V voltage for Arduino , in one of my projects , I need work with 3V , so I add a IC called "LM317" to provide 3V from 5V [ch65292]the data of LM317 : Intelligent Power and Sensing Technologies | onsemi
hope it is helpful
hi there,
me too, was thinking about designing kind of a micro-arduino running on 3,3 V. i don't know either if the atmega8 and atmega8L are fully exchangable.
does anyone know if burning the bootloader (for example) would just work using arduino IDE ?
i would have already tried it if i had an avr-isp :-/ but since i couldn't find a cheap one that works on a mac & with arduino (serial port+ STK500), i decided to just wait for someone with a windows pc.
i'm glad the forum has gotten reorganized.
@mellis: maybe we can get devolopment section in the hardware category, to start working on arduino variants?
best,
kuk
I think another solution is to hook up a 3V source in the power connector...
and be sure to change the jumpers near the usb board
but I don't know how the microcontroller will feel about receiving the 5V from the USB if you plug it in fo programming
fallen...how do you do that? did you solder the LM317 on the board instead of the 7805?
cheers
b.
beltran : No, I need both 5V and 3V , I add LM317 after 7805 [ch65292] and it give 3V power to one IC in my board which need 3V. I can't get the circuit now ( I'm in school , the draft of circuit is at home) , I will post it next time.
and you can see this circuit in my flickr , is a very easy way to get Atmega8 work in 3.3V:
i am also interested in the atmega8(L). the only problem i see is that the (L) version only runs at 8Mhz... not sure what impact this would have on the IDE (i'm more of a hardware guy ;)) if someone who knows the IDE well could chime in i would appreciate it greatly.
also, if you look at the datasheet for the atmega8: http://www.atmel.fi/dyn/resources/prod_documents/doc2486.pdf
you'll see that it supports 7 power modes, and i'm extremely interested in how one could access these through arduino/C. IMO, sleep modes would be essential to making a tiny battery powered version of arduino successful... or usefull/worthwile depending on your point of view.
Hej guys,
the problem is obviously that the ATMEGA8 on the Arduino board has a 16MHz clock, while the ATMEGA8(L) running on 3V has a maximum clock of 8MHz. This requires hacking the "wiring.c" library and others into the "/lib/targets/arduino" folder. And, of course, getting rid of the Xtal.
If anyone does it, please post it so that we have it documented. I've done it once, but I am too busy until July to document any new hacks.
/David
We did it with Low Power version. It works well. It's fast enough and I'ven't worked with the normal (16Mhz) yet, so I can't see the difference. There was some tricks about the clock in the preferences files and you have to lie to the arduino about the baud rates (while it's twice slower). But it works.
But it's still battery hungry, while we haven't found the way to put arduino in a sleep mode. From the test, it was around 30mA. Did someone had found how to turn the arduino in sleep mode?
can you post the changes needed in the prefs? very interested in this!
still stuck on the sleep mode though... perhaps one of the creators or IDE programmers could shed some light?
All you have to change in preference file it's
build_cpu = 16000000L (to)
build_cpu = 8000000L
That's it. You don't have to recompile arduino.
You'll have to use your programmer to load the bootloader on (it works with 5v).
We did recompile the bootloader, but it was to turn off a pin for our Wifi device during the boot sequence. Otherwise, the Atmel go in reprogramming mode.
Now, you may have problems to communicate with the board, because you have to consider that baudrates are twice slower. You might tweak the baudrates by a factor twice more rapid.
thanks for the pointer... have you run arduino with the baud set at 38400?
concerning communications problems, did you encounter problems when loading your program from arduino, or general serial communication to the cpu?
also, regarding your tests and the draw of 30mA... was this while a program was looping or idle. it occurred to me that the draw shouldn't be that different between standard and low power revisions of the atmega8, just the supply voltage... but to be honest its just speculation 
I should verify, but I guess it was 38400.
We tried many different combinations, I guess it was 38400 for bootloading.
We had issues also with the serial device that we used.
30mA was when looping. I don't know how to do idle ( you mean using delay() )?
BTW we had problems with Baudrates with the USB arduino. I tried different baudrates, but we couldn't get better than a certain rate. Is there a known issue with the serial baudrate from Processing. I think that it could be a general problem because I had a similar problem with Wiring once.
not sure of a "known issue" with processing, but i'll look into it on my end. the ideas i have for this are really just stand alone intelligent objects, so i'm not sure if i'll be interfacing it with processing yet.
as far as idling goes, i believe the C funtions "abort" or "exit" will halt a program so you can measure the idle draw. haven't done much C though so i'm not positive... i'll check on my wiring board tonight though.
found this link, but i'm at work at the moment and don't have time to read it thoroughly... might help with the sleep issue.
Thanks so much for posting this. I was able to boot load and run the low voltage version just fine. With Arduino 5, in the prefrences I changed:
build.f_cpu=16000000L
to
build.f_cpu=8000000L
Cool. It's possible a few things (e.g. analogRead()) may not work (or not work properly) if you're running at a different clock speed. Let us know if you have any problems.