This question is certainly in the minds of many electronics makers:
As an Arduino maker I considered upgrading some designs to STM32. So I ran preliminary tests. My first surprise was that my code was using much more storage space and I had to move to devices with even more flash and RAM. The fact that these devices run in 3.3V is another concern.
I will publish a paper on how to choose the rigt MCU for Arduino projects later. For now, let’s focus on the storage capabilities and resources needed to run a program created in the Arduino IDE.
The following table shows the storage capabilities and resources needed to run blink for a couple of MCUs. Painted in green are negligible consumption of less or equal to 1% and painted in yellow are consumptions above 1%. You will certainly be quite surprised:
| Arduino Uno / Nano Arduino core | 644 Narrow MightyCore | 1284 Narrow MightyCore | Arduino Mega Arduino core | Arduino Zero Arduino core | Cortex M3 Blue pill STM32duino core | Cortex M4 Arduino core_STM32 | ESP32 Arduino -esp32 core |
|
|---|---|---|---|---|---|---|---|---|
| MCU | Atmega328 | Atmega644 | Atmega1284 | Atmega2560 | SAMD21G18 | STM32F103C8 | STM32F401RC | ESP32WROOM |
| Flash (Kb) | 32 | 64 | 128 | 256 | 256 | 64 | 256 | 1280 |
| RAM (Kb) | 2 | 4 | 16 | 8 | 32 | 20 | 64 | 320 |
| EEPROM (Kb) | 1 | 2 | 4 | 4 | ||||
| Bootloader size (Kb) | 0.5 | 1 | 1 | 8 | 16 | 20 | 20 | In ROM. |
| "Blink" used Flash | 930 (3%) | 1122 (1%) | 1214 (0%) | 1460 (0%) | 10624 (4%) | 15828 (24%) | 23516 (4%) | 194472 (14%) |
| "Blink" used RAM | 9 (0%) | 9 (0%) | 9 (0%) | 9 (0%) | 2732 (8%) | 3088 (15%) | 3244 (1%) | 13332 (4%) |
So we can see that
The conclusion of this raw test is that if you don’t need the extra features of 32 bits MCUs (like many communication ports, more pins, possibly faster SPI etc), but your program needs a lot of flash and RAM, it is really worth considering last generation 8 bits MCUs. These devices architecture is mature. They are running pretty well, and offer huge storage capabilities, to the opposite of what we naturally believe.
