Is my atmega2560 schematic correct?

Question

I'm designing a custom board with an atmega2560. It will be programmed using ArduinoISP. I want to be sure that i have made no mistakes on my schematic design before I order it. I folloud the schematic for the arduino mega 2560 from the arduino website. For the basic function of uploading a sketch is my design correct?

I can upload the full schematic on pdf if you need it but it just contains some ICs for the final board.enter image description here

This is the pcb design as asked in the comments!

• Ignacio Vazquez-Abrams: You want us to evaluate a board you've designed but won't show us the gerbers? How are we supposed to be able to answer that?
• Frank Fourlas: I would be happy to show you the "gerbers" if I knew what they are!
• Ignacio Vazquez-Abrams: They're what you send to the board house in order to have them actually make the board. Load them into a viewer and post the images here.
• Ignacio Vazquez-Abrams: You need to read AVR042.
• Edgar Bonet: Atmel recommends to have one decoupling cap per VCC/GND pair, and to place it as close to the pair as possible.

Answer 1

for the basic function of uploading a sketch your board schematics is indeed correct and going to work. I can't say much on the PCB as what you have posted is a partial design, in particular it doesn't show the solder mask expansion and other details which might greatly influence the final result.

Please also note you don't need a reset button, a voltage regulator nor an external oscillator for the basic function of uploading a sketch, but I believe you also want to have the ability to run the sketch without the programmer being attached...

• Frank Fourlas: Thank you very much. I actually do want it to run without the programer and the PCB is indeed partial as the final design will have lots of junk stuck on it. But thanks anyway, really helpful!
• Edgar Bonet: You don't need the crystal on the very first upload. However, once you have programmed the fuses to have the AVR clocked off the crystal, you will need it for any subsequent upload.
• Roberto Lo Giacco: @EdgarBonet you are right, but he might also decide to program the fuses so the internal 8MHz oscillator is used... It really depends on what he wants to do with it. I have my own designs running at 3.3V 8MHz internal in order to trim down costs.
• Edgar Bonet: See the schematic and the PCB design in the question: there is a crystal with matching caps connected to XTAL1/XTAL2. I would make little sense have that crystal and program the fuses to use the internal RC oscillator.
• Roberto Lo Giacco: @EdgarBonet I am saying the crystal is not mandatory.... you say the cristal is needed with certain fuses, I say the fuses can be changed and you get back to the presence of the crystal?!? I am saying the crystal is OPTIONAL and I agreed with you it would than require a proper setting on the fuses. Going back to the schematics makes no sense whatsoever to me.