update title and detail about compatible boards

Author: Renat0Ribeir0

content/Hardware Support/Generic/If-Arduino-UNO-Rev1-or-Rev3-or-Mega-is-not-recognized-by-the-computer.md

@@ -0,0 +1,13 @@
+---
+title: "If Arduino UNO (Rev1 or Rev3) or Mega is not recognized by the computer"
+id: 4411209176722
+---
+
+Missing or corrupted **USB-to-Serial** firmware can cause UNO (Rev1 and Rev3) and Mega boards to be recognized as any of the following:
+
+- Unknown Device
+- Composite Device
+- ATmega16u2 DFU
+- Atmega8U2 DFU
+
+Resolve the issue by [flashing the USB-to-Serial firmware in DFU (Device Firmware Update) mode](https://support.arduino.cc/hc/en-us/articles/4408887452434).