ESP32编译时的一些问题

1. 在编译带psram模块的固件时，常规psram和psram-oct的区别
   参考https://iot.stackexchange.com/questions/6608/unable-to-run-micropython-on-esp32-wroom
   
   上图是部分esp32-s3模块的flash类型和psram类型情况，在psram为2M时，使用的是QuadSPI，则选择常规psram。psram为8M时，使用的是OctalSPI，选择psram-oct选项
   对应./micropython/ports/esp32/boards里的sdkconfig.spiram或sdkconfig.spiram_oct配置
   所有芯片/模组的psram类型可以在乐鑫官方的选型工具中查看：
   (https://products.espressif.com/#/product-selector?language=zh&names=)

2. 在psram为8M时，在micropython里能利用上全部的8M内存吗？
   参考https://github.com/orgs/micropython/discussions/11018
   不可以，因为esp32的关系，在系统默认的情况时，只能使用4M内存。

3. 自定义固件创建流程, 这里我使用esp32 8M flash, 8M psram模块.

   • micropython\ports\esp32\boards\ESP32_GENERIC中创建新的sdkconfig, 我把它起名叫sdkconfig.custom

     # MicroPython on ESP32, ESP IDF configuration with SPIRAM support
   
     CONFIG_SPIRAM=y
     CONFIG_SPIRAM_CACHE_WORKAROUND=y
     CONFIG_SPIRAM_IGNORE_NOTFOUND=y
     CONFIG_SPIRAM_USE_MALLOC=y
     CONFIG_SPIRAM_MODE_QUAD=
     CONFIG_SPIRAM_MODE_OCT=y
   
     # This is the threshold for preferring small allocations from internal memory
     # first, before failing over to PSRAM.
     CONFIG_SPIRAM_MALLOC_ALWAYSINTERNAL=8192
   
     # SPIRAM increases the size of the firmware and overflows iram0_0_seg, due
     # to PSRAM bug workarounds.  Apply some options to reduce the firmware size.
     CONFIG_COMPILER_OPTIMIZATION_SIZE=y
     CONFIG_COMPILER_OPTIMIZATION_CHECKS_SILENT=y
     # CONFIG_RINGBUF_PLACE_FUNCTIONS_INTO_FLASH=y # Workaround required: see main_esp32/linker.lf
     CONFIG_FREERTOS_PLACE_FUNCTIONS_INTO_FLASH=y
     CONFIG_FREERTOS_PLACE_SNAPSHOT_FUNS_INTO_FLASH=y
   
     # 8M flash
     CONFIG_ESPTOOLPY_FLASHSIZE_4MB=n
     CONFIG_ESPTOOLPY_FLASHSIZE_8MB=y
     CONFIG_ESPTOOLPY_FLASHSIZE_16MB=n
     CONFIG_PARTITION_TABLE_CUSTOM=y
     CONFIG_PARTITION_TABLE_CUSTOM_FILENAME="partitions-8MiB.csv"
   

   • micropython\ports\esp32\boards\ESP32_GENERIC\mpconfigboard.cmake中新增配置项

   if(MICROPY_BOARD_VARIANT STREQUAL "CUSTOM")
       set(SDKCONFIG_DEFAULTS
           ${SDKCONFIG_DEFAULTS}
           boards/ESP32_GENERIC/sdkconfig.custom
       )
   
       list(APPEND MICROPY_DEF_BOARD
           MICROPY_HW_BOARD_NAME="Generic ESP32 module with SPIRAM"
       )
   endif()
   

   • 删除已有的build文件夹, 否则新的sdkconfig文件不会生效
   • 进入micropython\ports\esp32, 执行指令
     make BOARD=ESP32_GENERIC BOARD_VARIANT=CUSTOM