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1

I have an Uno R3 on Mac with OS 10.15.4. I'm using the /dev/cu.usbmodem1432101 as serial port, AVRISP mall programmer.

I keep getting avrdude: stk500_getsync() not in sync: resp=0x00 errors, all 10 of them when I try to upload a sketch.
I have tried rebooting my Mac,
resetting the Uno (green light on, three blinks of the yellow light on the board
upload a simple sketch shown below.
void setup() {
// put your setup code here, to run once:

}

void loop() {
// put your main code here, to run repeatedly:

}

I have nothing plugged into the UNO other than the the USB cable

I am very new to all of this but I did go through some of the simple tutorials like the blinking LED. I was able to upload that sketch and a couple of others. Now NOTHING.

It seems from researching a solution to this problem that I'm not the only one. However, none of the solutions I read have helped. Thanks for any help.

2

Make sure you have the correct board selected from the Tools > Board menu.

Make sure you have selected the port of your Arduino board from the Tools > Port menu.

Sometimes the port will be labeled with the board name in the menu. Other times it will not. If you don’t know which port is your Arduino board, you can find it like this:

  • Unplug your Arduino board from the computer.
  • Tools > Port
  • Note the ports, if any, listed in the menu.
  • Close the Tools menu. The ports list is only updated when the Tools menu is re-opened, so this step is essential.
  • Plug your Arduino board into the computer.
  • Tools > Port - The new port listed in the menu is your Arduino board.
3

Thank you. I did all of the above and confirmed I have made the correct selections. However, I still cannot upload a sketch. In researching this problem, I came across one comment about the light at pin 13 always on. When I plug in my UNO, the yellow light blinks three times very quickly and then stays on.