Arduino for STM32

I feel like I'm being a bit of a pest. You folks have been more than helpful so far. However, VBAT doesn't just supply the back-up for the RTC, it powers up the entire board, quickly depleting the battery when you turn the normal supply off. This seems unusual to me as the typical development board (that has a built-in RTC) has VBAT just power up the RTC alone. I could instead use an external RTC as a workaround, but that seems silly.

I am fully aware that I on the F446RE board, I need to move a jumper or two, or perhaps solder or unsolder one or more of the bridges. I have studied the schematics and I am puzzled as to which one of the cornucopia of jumpers and bridges to alter from their defaults. (There are quite a few!)

If possible, I would like to:

1) Isolate VBAT so I can connect a back-up coin cell for the RTC, and not have it simply power the entire board.

2) Be able to power the board (and peripheral 3.3 volt modules like the display) solely via 3.3 volts for normal operation, yet still be able to easily update the software via the USB on occasion when needed whithout changing the jumpers or solder bridges.

With the default jumper and solder bridge configuration, it seems you can't simply power the board up via the 3.3 volt (CN7 Pin #16). Not sure, but it won't boot up unless you power up via the USB first. Once you have powered up via the USB, you can power Pin #16 and remove the USB power.

I really love this development board. It is absolutely _awesome_ for my application. Hopefully, it will be awhile before you hear from this "pest" again.

Bill D.

All should be explaind in Nucleo manual availbe on STM web page:
https://www.google.com/search?q=stm32+NUCLEO+f446re

I believe I have carefully reviewed the relevant manuals, including the schematic for the board:
https://github.com/Shikhargupta/MCU-Dev ... matics.pdf

Before I asked for a bit of guidance from this extremely helpful forum, I have spent a several days puzzling over this schematic, trying to figure out how I need to alter the state of the 60 solder bridges and/or 9 jumpers from their default state. I was hoping to get a bit of guidance before I started semi-randomly removing jumpers.

I suspect to accomplish simply powering up the main board on 3.3 volts, I need to change one (or both) of the jumpers on CN2 "ST-LINK". This is described (along with removing a portion of the board) on this link:
https://community.st.com/t5/stm32-mcus- ... d-p/306461

Will simply pulling these two ST-LINK jumpers do what I want?

Thanks in advance,
Bill D.
PS

(The link you provided only led to a google search results for NUCLEO STM32 boards )
https://www.google.com/search?q=stm32+NUCLEO+f446re

killacycle wrote: Mon Dec 02, 2024 4:08 am (The link you provided only led to a google search results for NUCLEO STM32 boards )
https://www.google.com/search?q=stm32+NUCLEO+f446re

Well... No one here is a mindreader. You got link to most common F466RE board.

I'm thinking I might be far better off putting in 7-12 volts into pin 24 of CN7 (VIN), or ~5 volts into pin 6 (E5V). Then move JP5 from pins 1-2 to 2-3 and pull JP1. I believe this will still allow Arduino IDE programming via the USB (without having to rearrange the jumpers once again.) I am not drawing heaps from the 3.3V, so this should work for me.

VBAT looks like it is directly connected to VDD. I see no solder bridge or jumper to decouple them. So the back-up battery for the RTC looks like it is hardwired to VDD. I guess I will use an external DS3231. Reading the DS3231 spec sheet, and comparing to the STM32 RTC spec sheet, it looks like the DS3231 will keep more accurate time, for what it is worth...

Looking forward,
Bill D.

PS
I took the time I should have initially and read through the manual again. Here is the link to the very helpful Nucleo 64 board manual where all this information can be found, (if you take the time to look ) :
https://www.st.com/resource/en/user_man ... ronics.pdf

You have to remove SB45 as it is described in the User man, default is ON:

SB45 (VBAT/VLCD)
ON VBAT or VLCD on STM32 is connected to VDD.
OFF VBAT or VLCD on STM32 is not connected to VDD.

Just the information I needed.
Thank you so much!

Bill D.