Memory-Mapped Flash
Overview
ESP32 features memory hardware which allows regions of flash memory to be mapped into instruction and data address spaces. This mapping works only for read operations. It is not possible to modify contents of flash memory by writing to a mapped memory region.
Mapping happens in 64 KB pages. Memory mapping hardware can map flash into the data address space and the instruction address space. See the technical reference manual for more details and limitations about memory mapping hardware. For more information, check ESP32 Flash Memory-Mapping.
Supported SoCs
All ESP32 SoCs support flash memory-mapped feature.
Building and Running
Make sure you have your board connected over USB port.
west build -b esp32s3_devkitm samples/boards/espressif/flash_memory_mapped
west flash
Sample Output
To check the output of this sample, run west espressif monitor or any other serial
console program (e.g., minicom, putty, screen, etc).
This example uses west espressif monitor, which automatically detects the serial
port at /dev/ttyUSB0:
$ west espressif monitor
The sample code erases the scratch area defined in DTS file and writes a 32-bytes data buffer in it. Next, it prints that region content using flash API read and also using memory-mapped pointer. Both readings should return the same value. Important to notice that writing using memory-mapped pointer is not allowed.
*** Booting Zephyr OS build v3.5.0-rc3-10-g3118724fa268 ***
[00:00:00.255,000] <inf> flash_memory_mapped: memory-mapped pointer address: 0x3c040000
[00:00:01.122,000] <inf> flash_memory_mapped: flash read using memory-mapped pointer
ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |........ ........
ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |........ ........
[00:00:01.122,000] <inf> flash_memory_mapped: writing 32-bytes data using flash API
[00:00:01.122,000] <inf> flash_memory_mapped: flash read using flash API
00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |........ ........
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f |........ ........
[00:00:01.122,000] <inf> flash_memory_mapped: flash read using memory-mapped pointer
00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f |........ ........
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f |........ ........