ESP32 Forum

Thanks for the very usefull comparison.

Partition api seems to be the best fit so far since it seems to be low memory cost and should cover my case with saving a few large objects (images) of same size, especially using mmap seems compelling.

2 more questions, though:

- are there any compelling examples using the partition_read/write and partition_mmap functions other than the test file at https://github.com/espressif/esp-idf/bl ... artition.c
If not... would i use the methods exacly as it is done in the test?
- is any of the flash write methods capable of saving non primitve typed data, e.g. data stored in a struct. In my case i would like to use rgbVal from the ws2812 library - my workaround was to serialize data into an array of uint8[3] and do the conversion where required.

one more question:
- what do you mean by "difficult to update the file reliably" ? What challenges would i face using mmap here?

Gregg

If you only need a single immutable file, theres also the option of letting the build embed it.
Example for a file called "what_time.raw":

Code: Select all

/* embedded file */
extern uint8_t file_start[] asm("_binary_what_time_raw_start");
extern uint8_t file_end[] asm("_binary_what_time_raw_end");

component.mk:

Code: Select all

COMPONENT_EMBED_FILES := what_time.raw

Thanks for this point. Very helpful for another area I am working in!

If you only need a single immutable file, theres also the option of letting the build embed it.
Example for a file called "what_time.raw":

Code: Select all

/* embedded file */
extern uint8_t file_start[] asm("_binary_what_time_raw_start");
extern uint8_t file_end[] asm("_binary_what_time_raw_end");

component.mk:

Code: Select all

COMPONENT_EMBED_FILES := what_time.raw

if we use files it like this then where it will be stored.
in flash,EEPROM or it comsumes code size?

ESP32 normally doesn't have EEPROM, so it gets stored in flash, in this case as part of the application.

ESP32 normally doesn't have EEPROM, so it gets stored in flash, in this case as part of the application.

I read it on forum that this embedded files stored in rodata of flash.
so is there limit in flash rodata to store files, beacause I want to store 350kb of files in flash.

Yes there is. The entirety of rodata should be <=4MiB, so if you only want to store 350K, you're good.

Yes there is. The entirety of rodata should be <=4MiB, so if you only want to store 350K, you're good.

Ok. thank you very much.

Yes there is. The entirety of rodata should be <=4MiB, so if you only want to store 350K, you're good.

Heyy ,
I have used component embed files. but my code size is increased.
How's that?

Yes, they effectively count as 'code size'.