Save a single byte onn flash is it possible?

RE: Save a single byte onn flash is it possible?

endnode — Wed, 24 May 2017 13:31:03 GMT

No, with flash technology you will always need to reserve at least one page if you want to do multiple write/erase cycles. That's kind of hard stop cause by physics and design of the chip.

RE: Save a single byte onn flash is it possible?

Mufasa1 — Wed, 24 May 2017 13:03:16 GMT

I was using the UICR one-time registers and planning to move to another solutions like FDS. the problem with UICR registers it is not flexible (does not alllow multiple writes/edit) and I wont like to use a whole flash page if I want to use few bytes FDS case. What other practical solution exists?

RE: Save a single byte onn flash is it possible?

endnode — Wed, 24 May 2017 08:24:14 GMT

What do you mean by "I was using the UICR for the task"? That is NVM region but with specific restrictions, you can basically just write one-time into few registers. For that classic routine should be used (as for any direct work with registers!): read out full 32-bit value, mask the bits you are modifying merge it with new value you want to push in. Then simply set the register (pointer to register 32-bit address in continuous address space of the chip) to new value and you are done. Or you meant UART not UICR? I'm confused.

RE: Save a single byte onn flash is it possible?

Mufasa1 — Wed, 24 May 2017 00:21:06 GMT

I was using the UICR for the task, but I would go into troubles If I want edit the data your options are FSD?

RE: Save a single byte onn flash is it possible?

endnode — Tue, 23 May 2017 21:07:30 GMT

The write command must contain 32 bits, that what I was saying. Sure you can "change" only single bit which will effectively mean that you will "write" single bit.

RE: Save a single byte onn flash is it possible?

HeS — Tue, 23 May 2017 21:01:53 GMT

Its possible to write single byte (bit:) into the flash. Rest of bytes (bits) in 32-bit word must be set to 0xFF.

RE: Save a single byte onn flash is it possible?

endnode — Tue, 23 May 2017 15:24:58 GMT

Sure, you can write single word (32 bits) into the flash. Just make sure it's "empty" (= 0xFFFFFFFF aka all bits set to 1) before writing otherwise your write will probably result into wrong data (flash technology cannot change 0 bits to 1 unless you erase whole page). This is one of main added values of all the pstorage/fstorage/FDS libraries, they should manage page erase, backup etc. so you do just "logical" operations and leave dealing with "physical" addressing to lower layer functions and module logic.