Circular Buffer in Flash

Question

I need to store items of varying length in a circular queue in a flash chip. Each item will have its encapsulation so I can figure out how big it is and where the next item

Answer 1

I think I get it now. It seems like your largest issue will be, having filled the available space for recording, what happens next? The new data should overwrite the oldest data, which is I believe what you mean by a circular buffer. But since the data is not fixed length you may overwrite more than one record.

I'm assuming that the amount of variability in length is high enough that padding everything out to a fixed length isn't an option.

Your write segment needs to keep track of the address that represents the start of the next record to write. If you know the size of a block to write ahead of time, you can tell if you are going to end up at the end of the logical buffer and start over at '0'. I wouldn't split a record up with some at the end and some at the beginning.

A separate register can track the beginning; this is the oldest data that hasn't been overwritten yet. If you went to read out the data this is where you would start.

The data writer then would check, given the write-start address and the length of data its about to commit, if it should bump the read register, which would examine the first block and see the length, and advance to the next record, until there is enough room to write whatever the data is. There will be a gap of junk data that lives between the end of the written data and the start of the oldest data, probably. But this way, you can just be writing an address or two as overhead, and not rearranging blocks.

At least, that's probably what I would do. HTH