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BeagleBone based Serial Terminal Server

Student: Harikrishnan R
Mentors: Michael Welling
Code: TBD


This project is currently just a proposal.


About me

IRC: illustris
School: BITS Pilani, Goa campus
Country: India
Primary language: English
Typical work hours: 11:30 PM to 4.30 PM UTC
Previous GSoC participation: No previous participation.

About my project

Project name: BeagleBone based Serial Terminal Server
Task Completion: Pull request.


Often in embedded development it is valuable to have a serial terminal server which can retain a serial port connection along with buffered past I/O separate from a typical host PC, either for longer term logging of serial port data or to enable remote management of a device via serial port. Commercial units which have this capability are very expensive, with even single port serial terminal servers consting hundreds of dollars. The BeagleBone has 4 highly capable UARTs exposed besides UART0 through the cape connectors. A simple cape hardware could easily enable a BeagleBone to physically have all the interfaces needed to be a serial terminal server.


The project will have the following features:

  1. User connects to the terminal server over SSH.
  2. A command line interface will allow users to configure and select the interfaces to monitor and log.
  3. Logs will be split and archived every 24 hours.
  4. User will be able to attach to and detach from individual serial terminal sessions, similar to tmux/screen.
  5. User will be able to view logged data from the serial device.
  6. Kermit style expect-send scripts can be attached to interfaces from the prompt.
  7. Arbitrary scripts/executables can be attached to interfaces for automation through redirection of stdio.
  8. Scripts can be scheduled for periodically connecting to devices, performing actions and logging the output.


  • A new user will be added to the BeagleBone for users to connect to.
  • The new user will have a custom prompt instead of bash.
  • termios will be used to configure serial interfaces.
  • Incoming data will be piped to a log file without buffering.
  • When a user attaches to a session, the log will be tailed to display the serial output.
  • Input from the user will be piped to the serial device in interactive mode.
  • A cron job will handle log archiving.
  • The native "expect" program will be used to parse expect scripts.
  • On running a script, the output of UART will be piped to the script, and the output of the script will be piped to UART.
  • scheduling of scripts will be handled by a separate thread.


Week Plan
1 Discuss with mentor and finalise available commands/features
2 Enable all UARTs, write code to read from UART and log
3 Implement non-interactive live log display
4 Implement piping of stdin to uart device
5 Implement basic attach/detach functionality
6 Implement "configure" CLI command to configure UARTs
7 Add scripting support
8 Add and test scripting support
9 Test
10 BUG fixing and documentation
11 BUG fixing and documentation
12 Package into installer

Experience and approach

As the controls engineering lead of Hyperloop India, I have worked extensively with embedded electronics and software. One of the nodes used in the pod electronics was built around a BeagleBone with a device tree overlay for enabling DCAN1. I have also ported FreeRTOS to a RISC-V processor I helped design.


What will you do if you get stuck on your project and your mentor isn’t around?
If Michael and Stephanie are unavailable, I would try asking for help on IRC. I would also consult relevant manpages and documentation.


This project will allow users to monitor up to 4 UART devices over ethernet without having to use either an expensive serial terminal server, or an always-online computer with USB hubs and multiple USB-TTL converters. This will also allow users to automate monitoring by using expect, python and other scripting languages.

Quotes from IRC:

2016 Mar 04 17:40:03 <m_w> I like the serial terminal idea

2016 Mar 04 17:43:02 * nerdboy would like to see a cape with a set of pins and db9's, each one selectable...

2016 Mar 04 17:44:45 <nerdboy> m_w: my really like that idea too, i might be able to talk her into co-mentor 2016 Mar 04 17:44:51 <nerdboy> *my boss even

2016 Mar 04 17:46:57 <nerdboy> use case is up to 5 controller boards 2016 Mar 04 17:47:04 <nerdboy> simultaneous

2017 Mar 16 16:00:53 <m_w> the trick is making an interface that is more user friendly 2017 Mar 16 16:01:45 <m_w> just ssh'ing into the target and running minicom is not going to be enough

2017 Mar 16 16:06:19 <m_w> perhaps a TUI or web interface to configure the terminals 2017 Mar 16 16:06:55 <m_w> baud rate, bits, parity, logging file, etc 2017 Mar 16 16:08:09 <m_w> another nice feature to have would be a hexadecimal viewer 2017 Mar 16 16:09:13 <m_w> perhaps timestamps would be useful 2017 Mar 16 16:10:12 <m_w> the trick is packaging the software in a way that you would expect from a consumer product

2017 Mar 19 17:48:08 <ordsen> m_w: hey I looked through commercial terminal servers and found that some companies also include pattern matching, messaging when certain events occur and tunneling to interconnect 2017 Mar 19 17:48:54 <m_w> maybe we can add some of those features as stretch goals

2018 Mar 20 15:57:15 <m_w_> serial logging and sessions are gimmies we need a UI of some sort and maybe some integrated scripting support 2018 Mar 20 15:58:28 <m_w_> this project was close to making the cut for the last few years so a good proposal would really up it's chances of being accepted

2018 Mar 20 16:19:28 <m_w_> illustris, is there going to be an attempt at making some supporting hardware? if so it needs to be ready soon

2018 Mar 20 16:24:46 <m_w_> scripting and logging are critical features

2018 Mar 20 16:52:42 <m_w_> serial automation is especially important in embedded test fixtures

2018 Mar 20 17:42:36 <m_w_> illustris, kermit allows for an expect like interface to poll for expected serial output and conditionally send data out 2018 Mar 20 17:43:11 <m_w_> not saying you have to use kermit but it would be nice to have similar features