Software » CANRec

Overwrite old data when card is full.
Simplest solution is to handle the start block.

Keep a distance to have it a bit fail-prove (current block may not overtake start block due to power losses).
The whole sd card size may be limited manually to a copy can be taken on PC.

The "middle" of start/end has to be calculated different.
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S E
M=(S+E)/2)=4.5

[0] [1] [2] [3] [4] [5] [6] [7] [8] [9]
E S
M=(S+E+10)/2=15/2=7.5

[0] [1] [2] [3] [4] [5] [6] [7] [8] [9]
E S
M=(S+E+10)/2=15/2=7.5