Serial Tap

Note

This page is for the Serial Tap plugin. For the board, please see the “Hardware Manual”.

The Serial Tap is a hardware sniffer for monitoring RS232, RS485, and TTL-level UART communications. The sniffer taps into the data and control lines of serial links and sends the recorded data to IO Ninja software in real time. Use this plugin to monitor all communications.

Basic Setup

Ensure your Serial Tap is connected to your serial device and your computer.

Please see the “IO Ninja Hardware Manual” for guidance on doing so.

In IO Ninja, click the “New Session” dropdown and select a new “Serial Tap” session.

If not selected automatically, select your Serial Tap from the “Tap:” dropdown.

Start capturing by clicking the “Capture” button located to the right of the “Tap:” dropdown.

Monitor traffic in the “Serial Tap” tab.

Adjust settings as needed via the “Settings” button (see “Settings” section below for details).

Settings

Setting	Description	Default
Tap	The Serial Tap that should be used.
Baud rate	The serial baud rate.	38400 bps
Data bits	Serial data bit count (word size). See available options.	8 bits
Parity	Serial parity check type. See available options.	None
Stop bits	Serial stop bit count. See available options.	1 bit
Flip DTE/DCE	Flip logical sides of the tap cable.	False
Read parallelism (Windows-only)	Maximum number of read requests to issue in parallel. Having more than one pending read at a time helps with increasing read throughput when incoming data arrives in rapid streams (after filling one user buffer, the kernel can immediately switch to the next one without any waiting). Increasing this number beyond 4 usually won’t yield any extra performance gains.	4
Read block size (B)	The size of each individual read block submitted to the underlying transport.	4KB
RX buffer size (B)	The full size of the incoming data (RX) buffer. Affects read throughput.	16KB
Keep read block size	Don’t merge read blocks in RX buffer. Incoming data blocks coming in quick succession can be merged together so that IO Ninja writes them to log as a whole. When this option is set to `True`, blocks are written to the log without merging, i.e., exactly as they are received from the underlying transport..	False
RX buffer full notifications	Toggle warnings in log about the incoming data (RX) buffer getting full.	False
Serial setting changes	Toggle notifications about serial setting (baud rate, data size, parity, stop bits, flow control) changes in the log.	on
DTR/RTS changes	Toggle notifications about control line (`DTR`, `RTS`) changes in the log.	on
DSR/CTS/DCD/RI changes	Toggle notifications about status line (`DSR`, `CTS`, `DCD`, `RI`) changes in the log.	on
Serial line errors	Toggle warning about serial line errors (`PARITY`, `FRAMING` and `BREAK`) in the log.	on

Data Bit Options

Option
5 bits
6 bits
7 bits
8 bits

Parity Options

Option	Description
None	No parity bit is used
Odd	Odd parity (parity bit is set when the number of logical ones in the UART frame is odd).
Even	Even parity (parity bit is set when the number of logical ones in the UART frame is even).
Mark	Parity bit is present and always set.
Space	Parity bit is present and always clear.

Stop Bit Options

Option
1 bit
1.5 bits
2 bits