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SD cards are slow [for low RAM systems]

A project log for Open LIDAR

This project is to build a motorized gimbal mount to convert a laser distance module into a 3d LIDAR.

caveradamcaver.adam 10/03/2016 at 13:030 Comments

I've been making progress on the project and have it very close to running. I was able to get some outputs yesterday, but VERY slowly. I've run into a problem where the SD card latency is a major issue in scanning speed. So instead of writing to the SD card every reading I need to save them up and send them in chunks. Unfortunately, I only have enough memory to save up to 640 bytes of information before sending it to the SD card. That means my scanner pauses every 320 readings [of two bytes per reading] in order to send the data to the SD card. It's taking 9 seconds to scan one pitch rotation and save to the card. This compares to 0.9 seconds to scan and throw the data out over serial.

Other than that, I had some issues with odd values being output. But, the TestSF30 function outputs correctly, so I may just need to compare the code for collecting and converting results.

I was trying to get a scan it late last night before I quit...but my batteries quit first. So, tomorrow night to get a scan out.

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