Hello ; First of all, please change the post topic to "general discussion" in order to get more interaction with your post since this is not 100% JLCPCB related post. About your request, you better search for the Arduino mega schematic instead of searching of the needed parts because you will have the BOM from the appropriate schematic, please check this public project that it shows what are the components that the mega has been built around : [https://easyeda.com/thiskiralex/arduino-mega-2560](https://easyeda.com/thiskiralex/arduino-mega-2560) Talking about the communication over serial port, if you are establishing this communication from any other external MCU straight to your Arduino MCU then just connect the TX of your Arduino to RX of the external MCU and RX of your Arduino to the TX of the external MCU and it should necessarily have both GND of both parts connected together (common ground) then make sure that you are having the same baud rate of the serial ports set in both MCUs (like 9600 bps). In case you are facing problem while sending data through TX RX of the Arduino from an external Device which has for example a USB port, then a USB to Serial converter is needed in this case, the Arduino Mega has a ATmega16U2 which is a 8bit AVR MCU that has a firmware uploaded to it to play the role of USB to serial converter.

I think you're looking in the wrong place. A quick Google search turns up: [https://www.element14.com/community/thread/42867/l/no-cost-reference-design-data-for-arduino-mega-2560](https://www.element14.com/community/thread/42867/l/no-cost-reference-design-data-for-arduino-mega-2560)

@andyfierman He is looking for the BOM list to solve another problem which is Serial communication issue, the link you have shared takes to another forum (not necessarily a reference design), I think that the post topic doesn't tell the main problem :) @Chris here is the official document of the Mega2560 schematic from Arduino website, you can check it to learn how they are establishing Serial communication (as I already mentioned in my previous comment, it is established through the firmware of a ATmega32U MCU) [https://store.arduino.cc/arduino-mega-2560-rev3](https://store.arduino.cc/arduino-mega-2560-rev3) If you are willing to get the BOM list then please download the "eagle files" from the same link and you can generate the BOM list from eagle then. Best of luck

I used the official Arduino Mega 2560 R3 eagle files to create the board. I know that the BOM is included with the Eagle files - the issue is that you cannot copy and paste that BOM into JLCPCB (at least not in a clean way that I'm aware of). There are parts that are not recognized by JLCPCB's import tool, JLCPCB does not carry the part needed, or the limit of extended parts is exceeded when trying to order an SMT assembly (which I need). I understand how serial communication is conducted between the ATmega 16U2 and the ATmega 2560 chips. I am able to flash both chips with a USBasp programmer via the ICSP pins at each respective chip and have the board recognized as an Arduino Mega 2560 in the Arduino IDE by both my Mac and my PC. The error occurs when trying to upload a sketch. I receive an 'avrdude: stk500v2_ReceiveMessage(): timeout'. As I've ruled out every other possibility, the cause must be the hardware. Thus, I am looking for a list of parts that someone has used to order an Arduino Mega 2560/Clone that is known to be compatible with JLCPCB's SMT assembly requirements (other than parts such as the usb connector, crystal oscillator, power jack, etc.). More information on the error message can be found here if it helps (though this is more for the programming side of things): [https://forum.arduino.cc/index.php?topic=704669.0](https://forum.arduino.cc/index.php?topic=704669.0)

@cnlsn007 Hello About the error message, do your ATmega MCU has the Arduino Bootloader in it. if you are getting the MCU from a supplier and just solder it to your board with no any intervention then don't expect it to receive codes from the IDE as long as it doesn't have the appropriate Bootloader.

@JLCPCBsupport yes. When I said "I am able to flash both chips" that means that I have flashed the bootloader to the 2560 and the appropriate .hex file for the m16U2 (all of this information is included in the link provided). The "supplier" is you. As stated in my previous comment, I use JLCPCB's SMT assembly service. To be clear, the only parts that I solder myself are the usb connector, crystal oscillator, power jack, (2) ICSP pins, and (2) reset buttons. All other components are SMD components added/supplied by JLCPCB.

@cnlsn007 If the problem is hardware (components) then nothing to do with the PCB and it would be better if you make a check on your schematic then double check the PCB design that you have ordered, maybe the MCU that you are using doesn't have the regular MCU signature of an ATmega2560!