Need help finding a simple, reliable RS232 data logger

Serial Communication
1

I’m looking for a straightforward RS232 data logger that’s reliable enough for continuous use in a small test setup. I’ve tried a couple of cheap USB adapters and free software tools, but I keep running into connection drops, missing data, or confusing configuration options. I don’t need advanced analytics—just stable logging, easy setup, and clear data export (CSV or similar). What hardware and software combinations have worked well for you, and are there any trusted brands or models I should focus on or avoid?

2

If you want simple and reliable for 24/7 RS232 logging, skip the random cheap USB dongles and hobby tools. They tend to drop the port, lose buffers, or choke when Windows decides to sleep or switch power states.

What has worked well for me in small test rigs:

  1. Hardware side
    • Use a decent USB to RS232 adapter
  • FTDI chipset, not Prolific clones.
  • Examples that stay stable under load: StarTech, Keyspan USA-19HS, or any adapter that clearly states FTDI and has proper drivers.
    • Turn off USB power saving in Windows
  • Device Manager → USB Root Hub → Power Management → uncheck “Allow the computer to turn off this device to save power.”
    • Fix COM port number
  • Assign a static COM number so your logger software does not get confused when you replug.
  1. Software side
    If you want something more robust than random freeware, look at “Serial Port Monitor” on Windows. It is not only a sniffer for debugging, it also works solidly as an RS232 data logger in continuous setups.

Key things it does well for long runs:
• Logs directly to file in real time, TXT or CSV.
• Handles multiple COM ports at once without crashes.
• Survives disconnects better than many free tools.
• Filters by direction, baud, or packet type so your log files stay readable.
• Shows timing and hex view if you need to debug framing or protocol issues.

They also have an RS232 data logging page here
RS232 data logger for continuous serial monitoring
That gives a decent rundown of use cases for test benches and long term logging.

If you want a simple workflow for your setup:
• Set Serial Port Monitor to log the COM port to a rolling file.
• Use a fixed baud, parity, stop bits that match your device.
• Enable timestamps in the log so you can line up events with your test data.
• Periodically rotate the logs via script if you run for days or weeks.

If you need something “fire and forget” on a stand alone box with no PC, then you would look at hardware loggers like:
• ICP DAS RS232 logger modules.
• Lascar EL-USB-5 (more limited, but works for slow streams).
Those work, but for lab style testing with a Windows box nearby, a decent FTDI adapter plus Serial Port Monitor tends to be cheaper, easier, and more flexible.

I had similar issues to you with free tools dropping the link after a few hours. Once I switched to an FTDI adapter and Serial Port Monitor, the same rig logged for 3 days straight without a single gap in the data. The only time it broke was when I forgot and let Windows update reboot the PC.

Need help finding a simple, reliable RS232 data logger
Need help finding a simple, reliable RS232 data logger1536×625 129 KB

1 Like
3

I ran into the same circus with flaky USB adapters and random freeware dropping the COM port after a few hours, so I feel your pain.

I mostly agree with @viajeroceleste on avoiding cheap adapters and letting Windows power management wreck everything, but I’ll throw in a few different angles so you’re not just reading the same recipe twice.

1. Skip USB entirely if you can
If this is a small, semi-permanent test setup and you’re sick of “USB device disconnected” drama, the most boring and reliable option I’ve had is:

  • Use a PC or small industrial box that still has a native RS232 port on the motherboard (or a proper PCIe serial card).
  • Brands like MOXA and Brainboxes PCIe serial cards are rock solid. Once installed, they basically never vanish like USB dongles.

For 24/7 logging, native UART or a decent PCIe card beats even FTDI USB in my experience. USB is fine, but if you want “plug it in and forget it for weeks,” hardware that looks like an actual COM port to the OS is less drama.

2. Consider OS choice & power behavior
If this is a dedicated logger box, I actually prefer a minimal Linux install for this stuff:

  • Set serial port with stty, log with screen, picocom, or a tiny Python script dumping to a file.
  • No surprise Windows Updates at 3AM, fewer sleep/hibernate “features” trying to be helpful.

That said, if you’re staying on Windows, at least go nuclear on power saving:

  • Disable sleep, hibernate, USB selective suspend, and “turn off hard disk after X minutes.”
  • Laptop lid closed behavior set to “do nothing” if you’re using a laptop as the logger.

3. Software: go for a proper logger, not just a terminal
A lot of “free tools” are just terminals with a Save to File checkbox bolted on. Those are fine for a quick test, but they choke on long unattended runs.

If you want something stable that behaves like a real RS232 data logger instead of a hobby toy, Serial Port Monitor actually is a solid choice. It’s not just a sniffer; it handles:

  • Continuous logging straight to file
  • Large logs without UI choking
  • Configurable timestamps and formats

In your case I’d set it up to:

  • Log to a simple text or CSV file
  • Enable timestamps with milliseconds
  • Use a rotating or daily log scheme so files do not grow into 20 GB monsters

I’ll disagree slightly with the idea that you always need filtering and hex views. For a small test setup where you just want to know “what did this device spit out over 48 hours,” a clean plain-text log with timestamps is usually enough. Debug views are nice, but they can distract from the main goal: don’t lose data.

If you want to try out Serial Port Monitor and similar tools, you can grab installers and related utilities from here:
RS232 logging tools and Serial Port Monitor downloads

4. Standalone hardware loggers when PCs are the enemy
If the PC itself is the least reliable part of your setup (IT pushes updates, users reboot, etc.), then a dedicated hardware logger really does make sense:

  • Look at industrial RS232 loggers or protocol analyzers that log directly to SD card.
  • Many of them run fanless, no OS updates, just power + serial cable + SD card.

I’m personally not a fan of the ultra-mini “USB stick style” loggers unless your data rate is low and you’re fine with limited configurability. For higher baud rates or constant streaming, I’d go for something with proper specs and clear buffer / storage limits.

5. Simple barebones script alternative
If you do not care about fancy UI and just want robustness, you can also:

  • Use a short Python script with pyserial that:
    • Opens COM port with fixed settings
    • Writes each received line to a log file
    • Flushes frequently to avoid big buffers
    • Optionally auto-reconnects if the port disappears

This avoids depending on some GUI tool and is easy to run as a service or scheduled task. For test benches this is sometimes the most “boring but works” solution.

TL;DR for a simple, reliable RS232 data logger:

  • Prefer native RS232 / PCIe serial card instead of random USB dongle if possible.
  • Kill every power saving / sleep feature on the machine.
  • Use a dedicated logging tool like Serial Port Monitor instead of generic freeware terminals.
  • Or go full-control with a tiny Python logger or a standalone hardware logger if you never want Windows involved at all.

Once I moved from “mystery USB dongle + free serial terminal” to “serious serial hardware + proper logger,” my overnight tests stopped randomly dying and I stopped babysitting COM ports like a full-time job.