Arduino Compatible Mega

Does anyone know what the difference Arduino Compatible Mega2560 ATmega2560-16AU USB Board to the Arduino USB Board Compatible ATmega2560 Mega2560 sold on DealExtreme. The first is U.S. 17.99 and U.S. 20.30 the second. Noted that it seems that the plate has two crystals. Grateful for help.
LINK Prime,
LINK second,

the first one has a ceramic resonator in place of the crystal

Thank you for your attention. I am wanting to purchase my first Arduino, but honestly do not know which model to choose the "Mega" who has the best cost / benefit ratio.

Actually, for you your first, either just an Uno or get the Uno and Mega.

There are infinitely more projects that are turnkey for an Uno that take a bit more work for the Mega. Only the UAV community and HTML users use the Mega to any degree.

That said. I got the one with the 16u2 since that is closest to the Mega2560 R3 (Still missing the SDA SCL pins). I could not tell if the other was a 8u2 or 16u2. But that using of the crystal instead of the resonator is intriguing. The Uno R3 clone looks real good and even has the extra SDA SCL pins.

Thank Spcomputing.

I would suggest a uno for your first, mega has many more pins and 4x the memory but for most of your projects your not going to need it, and it adds a extra bit of complexity as you run across things here and there that didnt take the mega's into consideration

And I would suggest a genuine Arduino as your first arduino :slight_smile: hehe so you support the project

the first one has a ceramic resonator in place of the crystal

noob question, whats the difference between the resonator and a crystal?

For all intents and purpose, a resonator "was" a cheaper option over a crystal, but the accuracy is approximately:

Crystal Frequency +/-0.002%
Resonator Frequency +/-0.5%

its not THAT big of a deal for most projects, unless you need like super fine critical timing ... I can run a TV display off of a resonator, that's about as fine as I get

Hi Guys (or maybe gals as well !)

I have started using an Arduino UNO R3 with some success but have run out of I/O particularly analogue inputs. I have thought of three possible approaches:

  1. Multiplex the analogues
  2. Use the Mega 2560 R3
  3. Use two UNOs “talking” to each other.

3 may be good as I can separate user interface from processing etc. Maybe use I2S ? although I’m already using an I2S LCD display.

I wonder if any more experienced members could advise. I would also like to know if my UNO software will run with minimal mods on a Mega. Obviously I/O pins would need mods. How about conditional compilation. I think I’ve seen some in a library package - I think it was Servo.

Any further advice or comments gratefully received.

Thanks in advance