Using MicroPython with 16MB Flash and 8MB PSRAM

[WolleKette]

I use the D32 Pro (V 2) Modul from WEMOS which has 16MB Flash and 8MB PSRAM.
And I use a MicroPython Version with support ffor SPIRAM from here.

But I can’t see the Memory in MicroPython. Neither do I see the 16MB flash with esp.flash_size() nor the 8MB with gc.mem_free(). In both cases I only get 4MB displayed.

I think I have a fundamental problem understanding this. Is it at all possible to use more than 4MB heap RAM in MicroPython?

[davefes]

I copied these instructions off a posting on the old forum. Best to search the archives as I have not tried these myself.

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a) create a partition table for that 8 MB flash and place it in the esp32 directory. The name is arbitrary. I named it partitions_8mb.csv. My copy:
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Name, Type, SubType, Offset, Size, Flags

Note: if you change the phy_init or app partition offset, make sure to change the offset in Kconfig.projbuild

nvs, data, nvs, 0x9000, 0x6000,
phy_init, data, phy, 0xf000, 0x1000,
factory, app, factory, 0x10000, 0x1F0000,
vfs, data, fat, 0x200000, 0x600000,
b) create a board definition subdirectory for that board. That could be a copy of the most similar board. I called it GENERIC_SPIRAM_8MB. But you can give it any suitable name. That name is used in the make command and in the changed mpconfigboard.cmake (see below).
c) create a file sdkconfig.board in the board directory which sets the flash size and partition table name. My version:
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CONFIG_ESPTOOLPY_FLASHSIZE_8MB=y
CONFIG_PARTITION_TABLE_CUSTOM=y
CONFIG_PARTITION_TABLE_CUSTOM_FILENAME="partitions_8mb.csv"
c) change the mpconfigboard.cmake file in adding the name of the sdkconfig.board file. Mine looks as follows after the change:
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set(SDKCONFIG_DEFAULTS
boards/sdkconfig.base
boards/sdkconfig.ble
boards/sdkconfig.spiram
boards/GENERIC_SPIRAM_8MB/sdkconfig.board
)

set(MICROPY_FROZEN_MANIFEST ${MICROPY_BOARD_DIR}/manifest.py)
Then you can build & flash the image with

make BOARD=<new_board_name> deploy

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[WolleKette]

That sounds complicated. If I understand you correctly, I have to compile my own MicroPython image just to use more memory? Really?

[mattytrentini]

I'll address the RAM query. No, the ESP32 can only address 4MB of memory. Even with 8MB PSRAM fitted only 4MB of it will be accessible. It's why there's a number of 'red note alerts' on the AliExpress Wemos page for the D32 Pro:

There actually is a way to make some use of the additional memory but it's awkward, of limited use, and not supported in MicroPython. I mention it here only for completeness but I wouldn't suggest using it. Espressif provide the himem allocation API. It allows you to split your general memory, allocating a portion of it to be bank-switched at runtime.

Himem is probably not worthwhile pursuing, especially with the newer ESP32-S2/S3 able to address more than 4MB RAM.

[WolleKette]

Thanks for the clarification!

[davefes]

Sorry I confused extending the RAM with extending the FLASH.