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So yesterday, I was able to upload/compile given example code to the Esp32 Huzzah board. Today I couldn't even compile. Even carefully using the tutorial adafruit provides.

I was getting errors as given below. How do I fix this?

C:\Users\YbSeconds\Documents\ArduinoData\packages\esp32\hardware\esp32\1.0.1/tools/sdk/lib\libesp32.a(cpu_start.o):(.literal.main_task+0x14): undefined reference to `app_main'

C:\Users\YbSeconds\Documents\ArduinoData\packages\esp32\hardware\esp32\1.0.1/tools/sdk/lib\libesp32.a(cpu_start.o): In function `main_task':

/Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/esp32/cpu_start.c:503: undefined reference to `app_main'

C:\Users\YBSECO~1\AppData\Local\Temp\arduino_cache_436740\core\core_b15e1ec95534e29a355269b84b798354.a(HardwareSerial.cpp.o):(.literal._ZN14HardwareSerial9availableEv+0x0): undefined reference to `uartAvailable'

C:\Users\YBSECO~1\AppData\Local\Temp\arduino_cache_436740\core\core_b15e1ec95534e29a355269b84b798354.a(HardwareSerial.cpp.o):(.literal._ZN14HardwareSerial4peekEv+0x0): undefined reference to `uartPeek'

C:\Users\YBSECO~1\AppData\Local\Temp\arduino_cache_436740\core\core_b15e1ec95534e29a355269b84b798354.a(HardwareSerial.cpp.o):(.literal._ZN14HardwareSerial4readEv+0x0): undefined reference to `uartRead'

C:\Users\YBSECO~1\AppData\Local\Temp\arduino_cache_436740\core\core_b15e1ec95534e29a355269b84b798354.a(HardwareSerial.cpp.o):(.literal._ZN14HardwareSerial5flushEv+0x0): undefined reference to `uartFlush'

C:\Users\YBSECO~1\AppData\Local\Temp\arduino_cache_436740\core\core_b15e1ec95534e29a355269b84b798354.a(HardwareSerial.cpp.o):(.literal._ZN14HardwareSerial5writeEh+0x0): undefined reference to `uartWrite'

C:\Users\YBSECO~1\AppData\Local\Temp\arduino_cache_436740\core\core_b15e1ec95534e29a355269b84b798354.a(HardwareSerial.cpp.o):(.literal._ZN14HardwareSerial5writeEPKhj+0x0): undefined reference to `uartWriteBuf'

C:\Users\YBSECO~1\AppData\Local\Temp\arduino_cache_436740\core\core_b15e1ec95534e29a355269b84b798354.a(HardwareSerial.cpp.o): In function `HardwareSerial::available()':

C:\Users\YbSeconds\Documents\ArduinoData\packages\esp32\hardware\esp32\1.0.1\cores\esp32/HardwareSerial.cpp:157: undefined reference to `uartAvailable'

C:\Users\YBSECO~1\AppData\Local\Temp\arduino_cache_436740\core\core_b15e1ec95534e29a355269b84b798354.a(HardwareSerial.cpp.o): In function `HardwareSerial::peek()':

C:\Users\YbSeconds\Documents\ArduinoData\packages\esp32\hardware\esp32\1.0.1\cores\esp32/HardwareSerial.cpp:157: undefined reference to `uartPeek'

C:\Users\YBSECO~1\AppData\Local\Temp\arduino_cache_436740\core\core_b15e1ec95534e29a355269b84b798354.a(HardwareSerial.cpp.o): In function `HardwareSerial::read()':

C:\Users\YbSeconds\Documents\ArduinoData\packages\esp32\hardware\esp32\1.0.1\cores\esp32/HardwareSerial.cpp:157: undefined reference to `uartRead'

C:\Users\YBSECO~1\AppData\Local\Temp\arduino_cache_436740\core\core_b15e1ec95534e29a355269b84b798354.a(HardwareSerial.cpp.o): In function `HardwareSerial::flush()':

C:\Users\YbSeconds\Documents\ArduinoData\packages\esp32\hardware\esp32\1.0.1\cores\esp32/HardwareSerial.cpp:157: undefined reference to `uartFlush'

C:\Users\YBSECO~1\AppData\Local\Temp\arduino_cache_436740\core\core_b15e1ec95534e29a355269b84b798354.a(HardwareSerial.cpp.o): In function `HardwareSerial::write(unsigned char)':

C:\Users\YbSeconds\Documents\ArduinoData\packages\esp32\hardware\esp32\1.0.1\cores\esp32/HardwareSerial.cpp:157: undefined reference to `uartWrite'

C:\Users\YBSECO~1\AppData\Local\Temp\arduino_cache_436740\core\core_b15e1ec95534e29a355269b84b798354.a(HardwareSerial.cpp.o): In function `HardwareSerial::write(unsigned char const*, unsigned int)':

C:\Users\YbSeconds\Documents\ArduinoData\packages\esp32\hardware\esp32\1.0.1\cores\esp32/HardwareSerial.cpp:157: undefined reference to `uartWriteBuf'

collect2.exe: error: ld returned 1 exit status

exit status 1
Error compiling for board Adafruit ESP32 Feather.
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So it turns out the problem is that you're using the esp32 1.0.1 library provided by espressif. I'm assuming you're using the Arduino IDE board manager URL: https://dl.espressif.com/dl/package_esp32_index.json

To fix this, don't use 1.0.1. Use 1.0.0! Remove 1.0.1 and install 1.0.0. That should get it to compile properly without the uart, app_main errors.

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