Only 30kB of memory available on reset on a STM32F407VE board (BLACK_F407VE)

[hacksterous]

I flashed the standard BLACK_F407VE firmware image from the top-of-the-tree code and see only 30kB free memory on an SoC that provides 192kB.

MicroPython v1.26.0-preview.218.g2ce63b142.dirty on 2025-06-18; MCUDEV STM32F407VE with STM32F407VE
Type "help()" for more information.
>>> import gc
>>> gc.mem_free()
29760
>>> gc.collect()
>>> gc.mem_free()
30064

What macros can I set to compile out unnecessary features and how? I don't need networking, webrepl, LWIP, SPI and I2C possibly more.
I have tried setting defines in ports/stm32/boards/BLACK_F407VE/mpconfigboard.h such as below and regenerating the firmware, but it didn't help.

#define MICROPY_HW_HAS_NETWORK      (0)

So, even though this board provides a goodly amount of memory, I can't even run the MicroPython editor here -- fails with memory allocate error.

How do I reduce the memory footprint on this board?

Thanks in advance!

[yn386]

Could you try the following patch?
If you don't need to use network, you can reduce the memory foot print by

• disabling ethernet in mpconfigboard.h
• removing lwip, ssl, mbedtls in mpconfigboard.mk

diff --git a/mpconfigboard.h b/mpconfigboard.h
index 1bb257c..a9a868a 100644
--- a/mpconfigboard.h
+++ b/mpconfigboard.h
@@ -169,7 +169,7 @@ extern struct _spi_bdev_t spi_bdev;
 // #define MICROPY_HW_USB_VBUS_DETECT_PIN (pin_A9)
 // #define MICROPY_HW_USB_OTG_ID_PIN      (pin_A10)
 
-// Ethernet via RMII
+#if 0 // Ethernet via RMII
 #define MICROPY_HW_ETH_MDC          (pin_C1)
 #define MICROPY_HW_ETH_MDIO         (pin_A2)
 #define MICROPY_HW_ETH_RMII_REF_CLK (pin_A1)
@@ -179,3 +179,4 @@ extern struct _spi_bdev_t spi_bdev;
 #define MICROPY_HW_ETH_RMII_TX_EN   (pin_B11)
 #define MICROPY_HW_ETH_RMII_TXD0    (pin_B12)
 #define MICROPY_HW_ETH_RMII_TXD1    (pin_B13)
+#endif
diff --git a/mpconfigboard.mk b/mpconfigboard.mk
index c678078..e94d45c 100644
--- a/mpconfigboard.mk
+++ b/mpconfigboard.mk
@@ -5,6 +5,6 @@ LD_FILES = boards/stm32f405.ld boards/common_ifs.ld
 TEXT0_ADDR = 0x08000000
 TEXT1_ADDR = 0x08020000
 
-MICROPY_PY_LWIP = 1
-MICROPY_PY_USSL = 1
-MICROPY_SSL_MBEDTLS = 1
+#MICROPY_PY_LWIP = 1
+#MICROPY_PY_USSL = 1
+#MICROPY_SSL_MBEDTLS = 1

After applying the patch, you will get about 100KB free memory on reset.

>>> import gc
>>> gc.mem_free()
101840

Note that STM32F407VE has 192KB RAM but you can use only 128KB as a heap of micropython because STM32F407VE's RAM is composed 128KB SRAM and 64KB CCMRAM which are not continuous (CCMRAM is used as internal filesystem cache).