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By mitchell_giese
I recently purchased a OpenLog Artemis (DEV-16832 ROHS) to do some high baud rate serial data logging. I was previously using the DEV-13712 ROHS but the 115200 max baud was not enough for my needs.

My setup is extremely simple, I have a device that takes usb-c power and outputs serial data at 3.0v. I am connecting both the OLA board and my device to the same power source (shared ground) via usb-c cables and then running a jumper cable between the tx line on my device and the rx pin on the OLA. I have configured both of the devices to operate at 500,000 baud. I have also updated the OLA to the latest available firmware and confirmed that enableSD=1 and logSerial=1. All other logging is disabled.

I have confirmed that 3v of serial data is coming across the tx line, but when I power them both on I have had very limited success getting the OLA to log the data. When I press the reset button to wake it from deep sleep, I see the stat light blinking rapidly indicating that something is writing to the SD card. When I power down the device and remove that card, the serialLog file is 0KB most of the time. I have gotten it to work a few times, and validated that the data is correct, but I can't consistently repeat whatever it is I am doing.

Any help will be greatly appreciated!
User avatar
By PaulZC

The only way to guarantee the serial log file is closed correctly is to add a stop-logging button on Pin 32. If you disconnect the power while the OLA is still logging, the file may be left open and will appear zero size. Please have a look at: ... figuration (Scroll down to the "Configure Power Options" section) ... iderations

Best wishes,
User avatar
By mitchell_giese
Thanks for the help Paul. I got the button wired up but I am still having some issues. If I let the logging go for a minute or 2 and then press the button it does nothing. The stat light continues to flash showing me data is still writing to the SD card. It is not until I actually disconnect the serial input and then press the button that the OLA goes to sleep and stops logging. Additionally, when reviewing the data after a successful power down from a 2+ minute logging session a large portion of the data seems to be corrupt. I have confirmed that the corruption is happening on the OLA side and that the average data rate should only be about 43 KB/s. Any more ideas as to how I might resolve this? Thanks!
User avatar
By PaulZC

In OLA terms, 43KB/s is a _lot_ of data. I suspect what is happening is that the OLA code is getting stuck in the "if serial data is available, write it to SD card" loop and is never getting as far as servicing the stop-logging button. Also, if the SD card write takes longer than usual - which it does occasionally as the card performs some internal juggling - then at that data rate you will get a serial buffer overflow and data will be lost.

Using a freshly-formatted SD card may help. Pleased make sure you use the official SD Association Formatter:

I'm afraid the standard OpenLog Artemis firmware is not a good choice for your application. It might be possible to write dedicated code to resolve this. The code would need two threads, one to place the serial data into a large ring buffer and a second to write data from the buffer to SD card.

Best wishes,
User avatar
By PaulZC
Hi @mitchell_giese,

I've been experimenting with a special build of the OpenLog Artemis firmware, dedicated to high speed serial logging. Now, don't get your hopes up... It doesn't (yet) do what you need. It works well at baud rates up to 230400, with near continuous logging. I've tested it with 10Hz NMEA data from a u-blox ZED-F9P and the log files are clean at ~80% duty, ~20KB/s. The wheels come off at 460800 baud for reasons I don't yet understand.

If you are able to drop the baud rate on your sensor down to 230400, this firmware should work well for you. ... ial_Logger

There are some bells and whistles I hope you will enjoy:
- You can echo the data back out on the TX pin if you want to
- It has built-in parsing / error checking for u-blox UBX and NMEA format data (I use this to check for dropped characters)
- The firmware will automatically open a new log file after a pre-defined interval or when you toggle Pin 11
- You can configure Pin 32 for stop-logging (like the regular OLA)
- If you enable the debug messages, you get periodic updates of the number of characters received
- You can timestamp the data using a pre-defined 'token' (like the regular OLA)

Please give it a try - and apologies again that it doesn't quite handle the data rate you need.

Best wishes,
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