After some months working with the Arduino uno wifi rev2 board, suddenly I got the message below when uploading any program. Tested in Mac, windows and different cables ...
Arduino: 1.8.9 (Mac OS X), Board: "Arduino Uno WiFi Rev2, ATMEGA328"
/Applications/Arduino.app/Contents/Java/arduino-builder -dump-prefs -logger=machine -hardware /Applications/Arduino.app/Contents/Java/hardware -hardware /Users/BTB/Library/Arduino15/packages -tools /Applications/Arduino.app/Contents/Java/tools-builder -tools /Applications/Arduino.app/Contents/Java/hardware/tools/avr -tools /Users/BTB/Library/Arduino15/packages -built-in-libraries /Applications/Arduino.app/Contents/Java/libraries -libraries /Users/BTB/Documents/Arduino/libraries -fqbn=arduino:megaavr:uno2018:mode=on -ide-version=10809 -build-path /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686 -warnings=none -build-cache /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_cache_611323 -prefs=build.warn_data_percentage=75 -prefs=runtime.tools.arduinoOTA.path=/Users/BTB/Library/Arduino15/packages/arduino/tools/arduinoOTA/1.2.1 -prefs=runtime.tools.arduinoOTA-1.2.1.path=/Users/BTB/Library/Arduino15/packages/arduino/tools/arduinoOTA/1.2.1 -prefs=runtime.tools.avr-gcc.path=/Users/BTB/Library/Arduino15/packages/arduino/tools/avr-gcc/5.4.0-atmel3.6.1-arduino2 -prefs=runtime.tools.avr-gcc-5.4.0-atmel3.6.1-arduino2.path=/Users/BTB/Library/Arduino15/packages/arduino/tools/avr-gcc/5.4.0-atmel3.6.1-arduino2 -prefs=runtime.tools.avrdude.path=/Users/BTB/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino14 -prefs=runtime.tools.avrdude-6.3.0-arduino14.path=/Users/BTB/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino14 -verbose /Applications/Arduino.app/Contents/Java/examples/01.Basics/Blink/Blink.ino
/Applications/Arduino.app/Contents/Java/arduino-builder -compile -logger=machine -hardware /Applications/Arduino.app/Contents/Java/hardware -hardware /Users/BTB/Library/Arduino15/packages -tools /Applications/Arduino.app/Contents/Java/tools-builder -tools /Applications/Arduino.app/Contents/Java/hardware/tools/avr -tools /Users/BTB/Library/Arduino15/packages -built-in-libraries /Applications/Arduino.app/Contents/Java/libraries -libraries /Users/BTB/Documents/Arduino/libraries -fqbn=arduino:megaavr:uno2018:mode=on -ide-version=10809 -build-path /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686 -warnings=none -build-cache /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_cache_611323 -prefs=build.warn_data_percentage=75 -prefs=runtime.tools.arduinoOTA.path=/Users/BTB/Library/Arduino15/packages/arduino/tools/arduinoOTA/1.2.1 -prefs=runtime.tools.arduinoOTA-1.2.1.path=/Users/BTB/Library/Arduino15/packages/arduino/tools/arduinoOTA/1.2.1 -prefs=runtime.tools.avr-gcc.path=/Users/BTB/Library/Arduino15/packages/arduino/tools/avr-gcc/5.4.0-atmel3.6.1-arduino2 -prefs=runtime.tools.avr-gcc-5.4.0-atmel3.6.1-arduino2.path=/Users/BTB/Library/Arduino15/packages/arduino/tools/avr-gcc/5.4.0-atmel3.6.1-arduino2 -prefs=runtime.tools.avrdude.path=/Users/BTB/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino14 -prefs=runtime.tools.avrdude-6.3.0-arduino14.path=/Users/BTB/Library/Arduino15/packages/arduino/tools/avrdude/6.3.0-arduino14 -verbose /Applications/Arduino.app/Contents/Java/examples/01.Basics/Blink/Blink.ino
Using board 'uno2018' from platform in folder: /Users/BTB/Library/Arduino15/packages/arduino/hardware/megaavr/1.6.24
Using core 'arduino' from platform in folder: /Users/BTB/Library/Arduino15/packages/arduino/hardware/megaavr/1.6.24
Detecting libraries used...
/Users/BTB/Library/Arduino15/packages/arduino/tools/avr-gcc/5.4.0-atmel3.6.1-arduino2/bin/avr-g++ -c -g -Os -w -std=gnu++11 -fpermissive -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -Wno-error=narrowing -flto -w -x c++ -E -CC -mmcu=atmega4809 -DF_CPU=16000000L -DARDUINO=10809 -DARDUINO_AVR_UNO_WIFI_REV2 -DARDUINO_ARCH_MEGAAVR -DUNO_WIFI_REV2_328MODE -I/Users/BTB/Library/Arduino15/packages/arduino/hardware/megaavr/1.6.24/cores/arduino/api/deprecated -I/Users/BTB/Library/Arduino15/packages/arduino/hardware/megaavr/1.6.24/cores/arduino -I/Users/BTB/Library/Arduino15/packages/arduino/hardware/megaavr/1.6.24/variants/uno2018 /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/sketch/Blink.ino.cpp -o /dev/null
Generating function prototypes...
/Users/BTB/Library/Arduino15/packages/arduino/tools/avr-gcc/5.4.0-atmel3.6.1-arduino2/bin/avr-g++ -c -g -Os -w -std=gnu++11 -fpermissive -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -Wno-error=narrowing -flto -w -x c++ -E -CC -mmcu=atmega4809 -DF_CPU=16000000L -DARDUINO=10809 -DARDUINO_AVR_UNO_WIFI_REV2 -DARDUINO_ARCH_MEGAAVR -DUNO_WIFI_REV2_328MODE -I/Users/BTB/Library/Arduino15/packages/arduino/hardware/megaavr/1.6.24/cores/arduino/api/deprecated -I/Users/BTB/Library/Arduino15/packages/arduino/hardware/megaavr/1.6.24/cores/arduino -I/Users/BTB/Library/Arduino15/packages/arduino/hardware/megaavr/1.6.24/variants/uno2018 /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/sketch/Blink.ino.cpp -o /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/preproc/ctags_target_for_gcc_minus_e.cpp
/Applications/Arduino.app/Contents/Java/tools-builder/ctags/5.8-arduino11/ctags -u --language-force=c++ -f - --c++-kinds=svpf --fields=KSTtzns --line-directives /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/preproc/ctags_target_for_gcc_minus_e.cpp
Compiling sketch...
/Users/BTB/Library/Arduino15/packages/arduino/tools/avr-gcc/5.4.0-atmel3.6.1-arduino2/bin/avr-g++ -c -g -Os -w -std=gnu++11 -fpermissive -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -Wno-error=narrowing -MMD -flto -mmcu=atmega4809 -DF_CPU=16000000L -DARDUINO=10809 -DARDUINO_AVR_UNO_WIFI_REV2 -DARDUINO_ARCH_MEGAAVR -DUNO_WIFI_REV2_328MODE -I/Users/BTB/Library/Arduino15/packages/arduino/hardware/megaavr/1.6.24/cores/arduino/api/deprecated -I/Users/BTB/Library/Arduino15/packages/arduino/hardware/megaavr/1.6.24/cores/arduino -I/Users/BTB/Library/Arduino15/packages/arduino/hardware/megaavr/1.6.24/variants/uno2018 /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/sketch/Blink.ino.cpp -o /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/sketch/Blink.ino.cpp.o
Compiling libraries...
Compiling core...
Using previously compiled file: /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/core/variant.c.o
Using precompiled core: /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_cache_611323/core/core_arduino_megaavr_uno2018_mode_on_e6754daa561557e34a3c7d8252f5bac7.a
Linking everything together...
/Users/BTB/Library/Arduino15/packages/arduino/tools/avr-gcc/5.4.0-atmel3.6.1-arduino2/bin/avr-gcc -w -Os -g -flto -fuse-linker-plugin -Wl,--gc-sections -mmcu=atmega4809 -o /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/Blink.ino.elf /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/sketch/Blink.ino.cpp.o /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/core/variant.c.o /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/../arduino_cache_611323/core/core_arduino_megaavr_uno2018_mode_on_e6754daa561557e34a3c7d8252f5bac7.a -L/var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686 -lm
/Users/BTB/Library/Arduino15/packages/arduino/tools/avr-gcc/5.4.0-atmel3.6.1-arduino2/bin/avr-objcopy -O ihex -j .eeprom --set-section-flags=.eeprom=alloc,load --no-change-warnings --change-section-lma .eeprom=0 /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/Blink.ino.elf /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/Blink.ino.eep
/Users/BTB/Library/Arduino15/packages/arduino/tools/avr-gcc/5.4.0-atmel3.6.1-arduino2/bin/avr-objcopy -O ihex -R .eeprom /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/Blink.ino.elf /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/Blink.ino.hex
/Users/BTB/Library/Arduino15/packages/arduino/tools/avr-gcc/5.4.0-atmel3.6.1-arduino2/bin/avr-size -A /var/folders/rq/05j9qrjj4s16s_pb24j6qzg00000gn/T/arduino_build_514686/Blink.ino.elf
Sketch uses 1534 bytes (3%) of program storage space. Maximum is 49152 bytes.
Global variables use 22 bytes (0%) of dynamic memory, leaving 6122 bytes for local variables. Maximum is 6144 bytes.
avrdude: bad response to enter progmode command: 0xa0
avr_read(): error reading address 0x0000
read operation failed for memory "signature"
avrdude: error reading signature data for part "ATmega4809", rc=-67
avrdude: error reading signature data, rc=-67
avrdude: error reading signature data, rc=-67
Update
Just tried with a 2nd Arduino UNO wifi rev-2 that was working this morning. Now I get the same error message and did not modified any line of code.
This is the sequence of how things happened:
I cannot upload any program
Please let me know if I could help testing anything
This bug has been solved in Arduino version 1.8.1
Go to Genuino> Tools> Board "Arduino Uno Wifi Rev2"> Boards Manager ... and update to 1.8.1 (or latest)