RTT to PTY bridge

This utility allows you to form a bridge between Segger's Real Time Transfer (RTT) and a pseudo-terminal interface (PTY).

It behaves similarly to common USB to serial adapters, instantiating a PTY device while the utility is running, allowing you to send and receive data through the device using any number of common utilities (minicom, etc.).

Requirements

Since RTT is a proprietary standard, it will only work with a Segger J-Link or compatible device, and you will need to download the appropriate jlink arm library (libjlinkarm.so on Linux, libjlinkarm.dylib on OS X).

The application will search for libjlinkarm.so in common paths by default, but you can specify the file location using the -j <filename> option.

Key Parameters

The following command-line parameters are available (rtt2pty --help):

rtt2pty: Segger RTT to PTY bridge
rtt2pty [-opt <param>]

Options:
       -d <devname>      Segger device name
       -s <serial>       J-Link serial number
       -S <speed>        SWD/JTAG speed
       -b <name>         Buffer name
       -2                Enable bi-directional comms
       -j <filename>     libjlinkarm.so/dylib location
       -p                Print list of available buffers

Device Name (-d <devname>)

The Segger target device name string. The default value is nrf52.

NOTE: You can get a full list of device names by opening JLinkExe and entering the following command: expdevlist <path to output file>.

Serial Number (-s <serial>)

If you have more than one J-Link connected to your computer, the first device found will be selected by default. You can indicate the device you intend to connect to by supplying the J-Link's serial number, which is visible any time you run JLinkExe.

Bi-directional Communication (-2)

By default, the tool only allows communication in one direction (target to PC). Setting the -2 flag allows communication in both directions.

Buffer name (-b)

Print available buffers with -p:

$ ./rtt2pty -p
Connected to:
  #################
  S/N: ############
Searching for RTT control block...
Up-buffers:
0 Terminal (size=4096)
1 Logger (size=1024)
2 btmonitor (size=1024)
Down-buffers:
0 Terminal (size=16)
1 Terminal (size=0)
2 Terminal (size=0)

Then open PTY to the selected buffer:

$ ./rtt2pty -b btmonitor
Connected to:
  #################
  S/N: ############
Searching for RTT control block...
Using up-buffer #2 (size=1024)
PTY name is /dev/pts/6

Example

On OS X, you can run the following command to open a PTY device with bi-directional communication over RTT:

$ ./rtt2pty -j libjlinkarm.dylib -2 1
Connected to:
  #################
  S/N: ############
Searching for RTT control block...
Using up-buffer #0 (size=1024)
Using down-buffer #0 (size=16)
PTY name is /dev/ttys003

You can then connect to the PTY using a tool like minicom as follows:

$ minicom -D /dev/ttys003