m_c
your correct the micro controller is a 3.3V device


looking at a photo of the UC300 it has a
MICROCHIP dsPIC33EP256
Click image for larger version.  Name: UC300 PIC chip.jpg  Views: 1947  Size: 169.7 KB  ID: 25785


from the MICROCHIP web site
Operating Voltage Range (V)
3 to 3.6

the dsPIC33EP256 Input/Output

• Sink/Source 10 mA on All Pins
• 5V Tolerant Pins
• Selectable Open-Drain, Pull-ups and Pull-Downs
• Up to 5 mA Overvoltage Clamp Current
• External Interrupts on All I/O pins

the UC300 board has a 5V supply connector
so the surface mount device between the 5V supply and PIC
must be a low drop out 3.3V regulator

John