Troubleshooting info for serial

README.md

@@ -6,3 +6,21 @@ At this moment it supports up to 6 fans, depending on board ([https://www.arduin
 ### ESP32 Users:
 #### AnalogWrite
 Install [ESP32_AnalogWrite](https://github.com/ERROPiX/ESP32_AnalogWrite)
+
+#### serial
+If you're getting an error like
+```
+Traceback (most recent call last):
+
+  File "C:\Program Files (x86)\Arduino\hardware\espressif\esp32/tools/esptool.py", line 25, in <module>
+
+    import serial
+
+ImportError: No module named serial
+
+exit status 1
+Error compiling for board ESP32 Dev Module.
+```
+then see [arduino-esp32](https://github.com/espressif/arduino-esp32/issues/13). TL;DR:
+
+```$ pip install pyserial```