I have an Arduino UNO I'm using with a Macbook Pro.
I'm getting the following error message when attempting to upload my program onto my ATMEGA328P:
"Problem uploading to board.
avrdude: stk500_recv(): programmer is not responding"
I was able to load programs onto it while I was breadboarding a project for school, with jumper wires connecting the pins over to the breadboard. Once I had my coding and breadboarding complete, I created a PCB and soldered all the components onto it. I forgot about needing a crystal and capacitor until after I had completed the entire board. I found this link on using the chip on it's own without needing the crystal or extra capacitors.
Unfortunately, after following the instructions, when I went to upload the sketch, it said "A0 not defined in this scope" highlighting where I defined a variable for a switch hooked up to my A0 pin. After looking online and seeing similar problems, I tried deleting and reinstalling the Arduino Software. Now it won't even reload the sketch on like I was able to previously. I simply get the above error message.
Did I screw with the bootloader or something, and do I now have to reburn it back on; or is there something else going on?