Maximum Logging Rates and Performance

Q&A forumCategory: QuestionsMaximum Logging Rates and Performance
Naterater asked 6 months ago

We are using the ZED-F9P receivers for sUAS navigation and post-processing photogrammetry. We struggle with momentary dropouts of observations.

What are the configurations you use for 5Hz or faster on UART1? We need a lot of messages, and might have to use higher baud rates, but then we cannot use the serial logger (maxes out at 115200).

It would be great to get to 20Hz (50ms update rate) with all constellations, but there are far too many dropouts to make that happen in the current state. Are there any tricks or tips for making this happen?

2 Answers
clive1 answered 6 months ago

The biggest trick is to make sure to cull messages on interfaces you are not using.
If you get “txbuf alloc” warnings your data loss is due to slow interfaces, with too much data. Disable messages on unused interfaces. Review stats from UBX-MON-IO / COMMS / TXBUF
115200 is going to limit you, need to find a better logger. A lot of the flight controllers with STM32 and microsd card use the most inefficient SPI 1-bit modes, you really want ones capable of sinking multiple megabytes per second.

amorosik answered 6 months ago

Can you suggest us some models capable of having high reading/writing performance?

clive1 replied 6 months ago

This isn’t my use case (predominantly ground based devices), not evaluated. Writing is the critical path here, and then how it loads the core task.

You’d want something will balls, and where they understood the problem/issue, and balanced those appropriately. Most FC are designed/coded by people focusing on different problems.
First Google hit for “flight controller 4-bit sdio”

HolyBro’s Durandal has a 4-bit SDIO, should be capable of many MB/s

The Pixhawk project FMUv5 has 4-bit SDIO/SDMMC

Something like this could be repurposed to high speed data-logging

clive1 replied 5 months ago