Powering STM32-F446RE with 3.7v battery and using ST-Link

[b.crowell5]

I need to power my microcontroller (https://www.st.com/en/microcontrollers-microprocessors/stm32f446re.html#overview) project using a 3.7v battery (https://www.adafruit.com/product/354) running through a battery charger/regulator (https://www.adafruit.com/product/4755) but I need to maintain the ability to program through the USB ST-Link. One of the manuals (https://www.st.com/resource/en/user_manual/um1724-stm32-nucleo64-boards-mb1136-stmicroelectronics.pdf) for the board says to remove SB2 and SB12 but it also mentions something about losing the ability to reprogram the board using the ST-Link. Perhaps I am misunderstanding the manual in some way? If you could provide me with step by step instructions for how to accomplish this that would be great. Don't be afraid to explain it to me like I'm 5 years old.

[xisco]

Hi,

There are two problems to solve:

1.- 3.7 V is over the maximum 3.6 V of the MCU, and the 3.7V will be more when the battery is charging.

You need to reduce this voltage using a DC/DC converter.

2.- The ST-link. You can connect only SWDIO, SWCLK and GND wires from ST-Link to MCU, keeping the MCU powered from its battery