I’ve had some issues flashing firmware as of late and it may just come down to a faulty ramps board. I wondered if it mattered or was required to have both the USB connection and the PSU powering at the same time as flashing. It’s been nearly 7 months since my last update but I’m pretty sure I had the power supply plugged in at that time. Basically I get a successful upload confirmation but none of my hosts I try can find the printer and I’ve also gone back and tried Marlin, sprinter, and repetier via the firmware builder. Driving me nuts.
Nope you don’t need the PSU for the arduino 2560. Are you sure you didn’t change the baud rate?
I’m not sure what happened but I noticed no matter what port I plugged into my com always said 6 in the arduino interface even if the device manager read 5. So I used another PC and after getting everything reinstalled I was able to finally flash it correctly and get stepper motor communication . But I will note that (No PSU) for future reference. I’m not sure about the other computer I may have to reinstall drivers again to get it to communicate cause it still won’t connect on that PC.