Something is very wrong.

This error: avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00 is occurring on two different Win 10 computers and on a Raspberry Pi as well. Also on three different Arduino boards.

Which Arduino(s)? Correct board selected? Correct COM port selected?

Is this the first time that you use the boards? Or did it suddenly happen?

All three boards were used the day before. This happens on two windows 10 computers and one Raspberry Pi. I did a loop back on the boards. I couldn’t do blink before the loop back. Afterward I could then I couldn’t compile anything larger. Then not even the blink.

Post the full error message regarding the compiling.

You haven't said which boards.

All three boards are uno. The message just repeats 10 times with the note that it will try 10 times. I’m using a iPad right now. I’ll go back in the lab and get the whole message.

urlonz14:
I did a loop back on the boards.

What was the result of the loop back test?

The loop back gave me an echo for everything I entered in the serial monitor. Here is the full error message when the uploads on all three UNO boards were tried on my current project and the blink example:

Arduino: 1.8.1 (Windows 10), Board: "Arduino/Genuino Uno"

Sketch uses 25950 bytes (80%) of program storage space. Maximum is 32256 bytes. Global variables use 1584 bytes (77%) of dynamic memory, leaving 464 bytes for local variables. Maximum is 2048 bytes. Low memory available, stability problems may occur. avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x73 avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x73 avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x73 avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x73 avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x73 avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x73 avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x73 avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x73 avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x73 avrdude: stk500_recv(): programmer is not responding Problem uploading to board. See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions. avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x73

This report would have more information with "Show verbose output during compilation" option enabled in File -> Preferences.

That is not a compilation error. It is an upload error. The compilation was successful.

Remove any connections to pins 0 and 1. These pins are used for communication with your computer, including uploads. Connecting anything to these pins can interfere with uploads.

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, 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
  • Plug your Arduino board into the computer.
  • Tools > Port - The new port listed in the menu is your Arduino board.

If the Tools > Port menu is grayed or the port of your Arduino does not appear on the menu:

  • Make sure your USB cable is fully inserted into the Arduino board and the computer.
  • You may need to install the driver for the USB-serial chip on your Arduino.
  • You may be using a charge-only or defective USB cable. Try a different cable or test your cable on another device to confirm that it works for data.
  • Using a USB 3.0 port on your computer may cause problems. Try a USB 2.0 port.

Thank you pert. I did all the above to no result. Then along about 2 AM I tried uploading small sketches to two of the boards and they up loaded just fine. What I was working on involved an ESP8266 WiFi board I think perhaps I need to go back and flash that board. Thank you everyone for your help.