NyamFlashLoader is a simple Windows program that allows you to flash STM32 microcontrollers via UART port.

NyamFlashLoader uses the DTR and RTS pins of the COM port to automatically activate the built-in bootloader and reboot the microcontroller. The connection diagram is shown in the program.

You only need a USB-UART adapter to download programs via the built-in STM32 bootloader. The program also has a manual bootloader activation mode.

NyamFlashLoader works at baudrate 115200. It is very slow. If you need more speed, you should buy ST-Link programmer.

Watch YouTube video below for details:

The algorithm for working with the built-in bootloader via the UART interface is described in the document AN2606 STM32 microcontroller system memory boot mode.

Before programming the microcontroller, make sure it supports simple bootloader entry via UART. This can be found in the document AN3155 USART protocol used in the STM32 bootloader. Unfortunately, not all STM32 microcontrollers support simple bootloader activation.

The program does not require installation, just download and run the EXE file:

After launching, the program will create a text file NyamFlashLoaderSTM32save.txt with saved operating settings.