Enable debug interface on Serail1

• Default disable the debug interface.

If you want to enable debug trace on Serial1 to debug corelib, follow these instructions.

1. Shut down the IDE
2. Go to Arduino15 directory

• Windows: C:\Users\<user>\AppData\Roaming\Arduino15
• OS X: ~/Library/Arduino15
• Linux: ~/.arduino15

3. Modify the platform.txt

• Find compiler.c.flags and add -DCONFIGURE_DEBUG_CORELIB_ENABLED at the end of this line
• Find compiler.cpp.flags and add -DCONFIGURE_DEBUG_CORELIB_ENABLED at the end of this line

4. Initial Serial1 in your sketch

• Add Serial1.begin(115200); in your setup()

5. Adjust the output level at log_init function in log.c