Trying to use this library with the latest Arduino IDE 1.8.13 results in the error: SparkFun_LED_8x7.cpp:637: undefined reference to `operator delete(void*, unsigned int)' There seems to be a problem with how the 'delete' operator is defined. Opening SparkFun_LED_8x7.cpp and changing the line: delete chaplex_; to free(chaplex_); fixes the issue.