Logging Much slower than predicted on OpenLog Artemis

Development Boards Artemis
1

I have my baud rate set to 460800. When only logging with the IMU data, the logging speed is predicted to have a max of 400hz but it only actually logs at 80hz. When I add the GPS to the mix, the actual logging speed drops to 5hz.

I need at least 160hz for my application. Preferably higher.

I’ve tried several micro sd card but I’ve had no luck going higher than 80hz.
I’ve also updated the firmware to see if that would help. It went from logging at 10hz to the 80hz I am currently stuck with.

Anything I can do to log faster?

2

Hi @mbsil ,

With the GNSS attached, you are limited to 10Hz. Some u-blox modules support faster update rates, but the OLA firmware doesn’t know what model of GNSS is attached and so uses 10Hz as the upper limit.

For IMU-only logging, you can achieve high rates. But, for best results, you need to disable terminal output (“Log to Terminal”). Even with the terminal baud rate set to 460800, the Serial prints will still slow down the rate you can achieve. You want the SD-writing to be the limiting factor.

I hope this helps,
Paul

3

Can I set up the logger to repeatedly log the last recived value from the ublox so I can still sample the ADC at a higher rate?

I also disabled terminal output but I am only at 100hz with the IMU alone. : /

4

Hi @mbsil ,

Not without modifying and recompiling the firmware. The OLA source code is fully open-source, if you want to try that.

Please tell us exactly what you are logging. The IMU only? Or the IMU plus ADC (Analog) voltages? Something is limiting the sample rate… But it is not clear to me what that could be.

Best,
Paul

5

I am only logging the IMU.

This is a sample of the log file

rtcDate,rtcTime,aX,aY,aZ,gX,gY,gZ,mX,mY,mZ,imu_degC,output_Hz,
07/15/2025,04:47:29.61,-536.62,216.80,-838.87,-5.96,1.96,0.82,1.50,-6.90,-9.45,31.91,0.0,
07/15/2025,04:47:29.62,-565.43,203.13,-827.64,-6.86,1.76,-2.73,1.20,-7.35,-9.75,31.72,100.0,
07/15/2025,04:47:29.63,-551.27,223.14,-842.29,-8.30,3.73,-0.37,1.35,-8.55,-8.10,31.91,100.0,
07/15/2025,04:47:29.64,-538.57,227.05,-851.07,-8.79,-5.40,4.34,1.35,-8.55,-8.10,31.72,133.333,
07/15/2025,04:47:29.65,-541.02,198.24,-852.54,-12.89,-16.70,5.15,1.35,-8.55,-8.10,32.01,125.0,
07/15/2025,04:47:29.66,-562.99,227.05,-827.64,-13.63,-26.22,10.56,1.50,-7.65,-9.0,32.01,100.0,
07/15/2025,04:47:29.67,-568.36,247.07,-783.69,-15.45,-25.27,11.75,2.25,-9.90,-8.70,32.10,116.667,
07/15/2025,04:47:29.68,-573.73,250.98,-747.07,-13.82,-20.34,11.47,2.25,-9.90,-8.70,32.01,114.286,
07/15/2025,04:47:29.69,-566.89,263.67,-732.42,-11.94,-12.24,8.81,0.45,-6.60,-7.35,32.10,112.500,
07/15/2025,04:47:29.70,-541.99,269.53,-738.28,-11.08,-2.63,8.57,3.0,-7.35,-7.95,32.01,111.111,
6

Removing temp logging and changing to micros instead of rtcDate/Time logs at 280hz. Logging is set to 360hz but I can live with this I guess.

I also found this issue for the gps so I am able to log with it now.

1 Like
7

Ah, yes! The autoPVT option! I had forgotten I added that… Thanks for the reminder! :grin: