user19892: I have a compact weatherproof enclosure and the onboard USB jack of my Mega is close to the edge. I didn't want to add a bulky weatherproof USB jack, so I'd like to just leave a female USB pigtail loose inside the enclosure. 
The only thing is, I want to avoid the extra assembly step of soldering leads directly to the lugs on the board. I'd like to make a shield instead, with screw lug headers to attach all my wires to. That way a lot of my connections can be solderless and the assembly tech can just plug in the shield. 
Can I connect the four wires of a USB cable to the header pins? I suspect I'd use Vin, GND, pin 0 and pin 1, but I'm not 100% sure. Thanks for your advice, gentlemen.

user37622: No. For many reasons. No. USB is not TTL. You need an adapter to connect rx/tx pins of arduino to USB. And the on-board adapter has the DTR line connected to reset the Atmega before writing a program into it. Without it, you would need to push the reset button in the right moment.

19892: <p>I have a compact weatherproof enclosure and the onboard USB jack of my Mega is close to the edge. I didn't want to add a bulky weatherproof USB jack, so I'd like to just leave a female USB pigtail loose inside the enclosure. </p>

<p>The only thing is, I want to avoid the extra assembly step of soldering leads directly to the lugs on the board. I'd like to make a shield instead, with screw lug headers to attach all my wires to. That way a lot of my connections can be solderless and the assembly tech can just plug in the shield. </p>

<p>Can I connect the four wires of a USB cable to the header pins? I suspect I'd use Vin, GND, pin 0 and pin 1, but I'm not 100% sure. Thanks for your advice, gentlemen.</p>
 37622: <p>No. For many reasons. No. USB is not TTL. You need an adapter to connect rx/tx pins of arduino to USB. And the on-board adapter has the DTR line connected to reset the Atmega before writing a program into it. Without it, you would need to push the reset button in the right moment.</p>
