battery powered STM32 H407

[andrewg]

i'm exploring options for a wearable / little project. I stumbled into STM32 H407 and OLIMEXINO-STM32 (maple).

While it'd seemed maple could satisfy the battery (lipo) powered use case, STM32 H407 is apparently the 'bigger/better maple'. The original maple seemed rather limited in memory and storage constraints.

The user manual/guide appparently mentioned:
http://www.olimex.com/Products/ARM/ST/STM32-H407/open-source-hardware
http://www.olimex.com/Products/ARM/ST/STM32-H407/resources/STM32-H407.pdf

The board is powered in one of the following ways: 1) by PWR jack, 2) by JTAG/SWD 3)  3) by USB-OTG

The power supply circuit of STM32-H407 allows flexible input supply from 6V to 16V direct
current. This means a wide range of power supplies, adapters, converters are applicable. The
maximum amperage the board can draw is 1A.

The Li-Po battery connector cannot be used to fully power the board. It's function is to give an
option to save internal data if the board needs to be relocated. It will keep the RTC alive, for
instance.

Getting a > 6V battery 'wearable (i.e. light / small / high capacity)' power source via PWR jack is quite a challenge especially if I'd need it to last say at least a day or two.

I'm thinking of another 2 options, plugging a 5V li-po 'power bank' (those for charging mobile phones). The issue is that the micro usb-otg connector may just disconnect due to body movements.

And a 'last resort' is: could i hack a li-po battery (i.e. 3.7-4.3v) contraption to directly supply power throught the JTAG/SWD connector? This may pump 3.7V when the battery is fully charged right into the board which apparently have a VCC of 3.3 volts limit? too high a voltage? would that supply the processor adequately for processing, SD card storage and perhaps use of the ADC?

Or is there a better way to battery power the STM32 H407?

[LubOlimex]

Hey there,

Few comments:

Overall, STM32-H407 and STM32-E407 were designed mainly as R&D boards. The design doesn't allow powering only via Li-Po battery.

Pin 19 of the JTAG connector requires 5V of voltage - Li-Po battery would not do the job. Using 3.7V with the board is not recommended and some of the peripherals would not work properly. The only battery option is the provided back-up battery connector but it requires a 3V battery (it keeps up the backup domain - RTC registers, RTC backup register and backup SRAM - when there is no other power supply applied).

Also consider that STM32-H407 is quite bigger than OLIMEXINO-STM32 - usually size is important for wearable electronics.

Best regards,
Lub/OLIMEX

[andrewg]

hi lub, thanks much for the reply. i've actually just bought/ordered both OLIMEXINO-STM32 and STM32 H407

i'd 1st try to live with the OLIMEXINO-STM32, i still feel 20k of dram (rather sram) and 128k of storage in the OLIMEXINO-STM32 is still pretty much a squeeze (but yeah it does battery powered built right into it)

i'd think for 'real' IOT / wearables & such gadgets STM32 F4 is still very much needed to provide more room : storage & ram for the rather ambitious projects these days, i think arduino as a 'platform' has 'grown up' & we are moving towards 'full blown smart watches' style of projects