Blink on STM32L031K6T6

[ITstreet1]

The regular Blink sketch on STM32L031K6T6 eats 65% of memory. The basic OLED example with the Adafruit lib can't compile. It turns out that 32KB STM32 MCUs are not usable in the Arduino world. Let's say I want to use OLED and SX1276. On ATmega32p, this is not a problem.

Is there a way to make Arduino IDE use waaaaaay less memory for the STM32 MCUs?

[fpistm]

Hi @ITstreet1
yes 32k mcu are very limited with the core. And I don't think you can succeed with OLED and Sx1276 libraries.

you can disable all useless features. This will reduce the size of binary.
https://github.com/stm32duino/Arduino_Core_STM32/wiki/HAL-configuration#list-of-hal__module_disabled-definition

Made a try with the displayOnOffTest from Adafruit SSD1351 and have region `FLASH' overflowed by 104 bytes after some customization.
If the Serial is not required then disable it would help but the Adafruit library required to have it same for I2C and SPI. I would be fine to be able to disable one of the two interface.

Optimize for debugging disabled
Add build_opt.h with:

-DHAL_ADC_MODULE_DISABLED
-DHAL_RTC_MODULE_DISABLED
-DHAL_TIM_MODULE_DISABLED
-DHAL_DAC_MODULE_DISABLED
-DHAL_EXTI_MODULE_DISABLED
-DHAL_ETH_MODULE_DISABLED
-DHAL_SD_MODULE_DISABLED
-DHAL_QSPI_MODULE_DISABLED

Customize some pinmap array:

const PinMap PinMap_UART_TX[] = {
  {PA_2_ALT1,  USART2,  STM_PIN_DATA(STM_MODE_AF_PP, LL_GPIO_PULL_UP, GPIO_AF4_USART2)},
  {NC,         NP,      0}
};

const PinMap PinMap_UART_RX[] = {
  {PA_15,     USART2,  STM_PIN_DATA(STM_MODE_AF_PP, LL_GPIO_PULL_UP, GPIO_AF4_USART2)},
  {NC,        NP,      0}
};

const PinMap PinMap_UART_RTS[] = {
    {NC,    NP,      0}
};
const PinMap PinMap_UART_CTS[] = {
  {NC,    NP,      0}
};

const PinMap PinMap_I2C_SDA[] = {
  {PB_7,  I2C1, STM_PIN_DATA(STM_MODE_AF_OD, LL_GPIO_PULL_NO, GPIO_AF1_I2C1)},
  {NC,    NP,   0}
};

const PinMap PinMap_I2C_SCL[] = {
  {PB_6, I2C1, STM_PIN_DATA(STM_MODE_AF_OD, LL_GPIO_PULL_NO, GPIO_AF1_I2C1)},
  {NC,   NP,   0}
};

const PinMap PinMap_SPI_MOSI[] = {

  {PB_5,  SPI1, STM_PIN_DATA(STM_MODE_AF_PP, LL_GPIO_PULL_UP, GPIO_AF0_SPI1)},
  {NC,    NP,   0}
};

const PinMap PinMap_SPI_MISO[] = {
  {PB_4,  SPI1, STM_PIN_DATA(STM_MODE_AF_PP, LL_GPIO_PULL_UP, GPIO_AF0_SPI1)},
  {NC,    NP,   0}
};

const PinMap PinMap_SPI_SCLK[] = {
  {PB_3, SPI1, STM_PIN_DATA(STM_MODE_AF_PP, LL_GPIO_PULL_UP, GPIO_AF0_SPI1)},
  {NC,   NP,   0}
};

const PinMap PinMap_SPI_SSEL[] = {
  {NC,    NP,   0}
};

For example with all HAL disabled, Serial disable and Optimize for debugging disabled, we can reach 4500 bytes.
Sketch uses 4500 bytes (13%) of program storage space. Maximum is 32768 bytes.
Global variables use 96 bytes (1%) of dynamic memory, leaving 8096 bytes for local variables. Maximum is 8192 bytes.

[ITstreet1]

As the HAL eats a lot of memory space, it would be nice to add an option that can disable everything that is not essential. This way, for a simple task, the STM32 MCUs are unusable in comparison to the ATmega328p. And the simple task is to read a temperature on, say, a BME280 and to print it on the OLED display. If a 32KB STM32 can't do that, and a 32KB AVR can, then things are clear.

It is ok to do all those changes you suggested, but those are a lot of fixes. It is much easier to move to another platform.

Thank you for your time.

[fpistm]

ATmega328p is a 8 bits and the core is optumized for limited number of board.
This cores supports several series and is 32bits.
I know there is some limitations against memory space.
The suggested changes are not fixes but customization.
As stated Adafruit libraries also requires some space as some useless features needs to be enabled even if not used. Maybe they can be disabled, I didn't check.