In System Programming of My Ardunio Mega 256 with 16x32 led matrix

Projects General Guidance
1

I am working on a project that is using an Adafruit 16x32 Led Matrix. Plugging the board into my PC with the Matrix attached is an issue. Currently I have the Matrix and Mega powered from an old Lenovo power adapter for a laptop. I have a 5v 5a regulator with a cut usb cable plugged into the Mega and another cable powering the Matrix. I am unplugging the matrix from the mega and unplugging the usb cable to the Mega - then plugging the Mega via usb to my PC.
I wanted to ask before I blew something up - Can I keep my ArduinoMega and Matrix powered via my regulated 5v lenovo supply, and use an ISP programmer to program the Mega at the same time. I was thinking of using a FTDI adapter I was using to program a Moteino. I was thinking I would just hook up 3 lines RX,TX, GND leaving out the 5 volt line. I don't want to have to keep plugging and unplugging my project as I am testing my code. As another thought I was thinking of further modifying my usb power cable to the Mega. Can I hook up the ground, and the two data lines to the pc, again leaving out the 5v line and program that way? So I'd have 5v from my power supply taking the place of the 5v from the PC.
Or possibly any recommends for an ISP that plugs into the ICSP port on the board for programming?

Or if I power the Mega via DC input, is it kosher to plug the Mega into a pc via the USB port at the same time?

Thanks,

MAB

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Arduino boards (5V) can be powered by some external power supply, at the power jack or Vcc input, and a PC can be connected to the USB connector at the same time. When programming via USB, the Rx and Tx lines should not be connected to further circuits, or a different programmer has to be used.

Other circuits can stay connected, provided they survive being powered on without defined levels on their input pins. When they have Enable lines, these can be pulled into disabled state by a resistor (10-50k), so that they can be overridden by output signals once the sketch has been booted.

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Thanks for the info. I was very worried about the USB getting plugged into my pc at the same time I'm applying power to the circuit from another source. I will be happily trying this tomorrow. :slight_smile: Thanks, Mab