Serial Tap Pro is a next-generation serial sniffer; the functional differences that distinguish it from the original Serial Tap (https://ioninja.com/hardware/serial-tap.html) are as follows.

Serial Tap Pro features:

• Galvanic isolation (for robustness and protection of all electrical circuits involved)
• Twice as high baud rates (2.5 Mbps in Serial Tap Pro vs 1 Mbps in Serial Tap)
• Automatic detection of baud rates and UART frame size (aka, ABR)
• Guaranteed correct sequencing of all events with hardware-generated microsecond timestamps (in contrast, Serial Tap uses two independent USB-to-UART channels, timestamped at the PC side)
• 9-bit data frame support (used by some industrial equipment)
• Half-duplex (two-wire) RS485 packet direction detection
• Data and status line injection (so Serial Tap Pro can effectively be used in lieu of any USB-to-RS232/485/TTL adapter)

Read more at the product page: https://ioninja.com/hardware/serial-tap-pro.html