[stm32f4xx] Custom Hardware?

[AwesomeCronk]

I want to develop a portable uPython interpreter. I want to be able to use unmodified firmware from the PyBoard with maybe a few additions to the libraries. Here is what I want:
-WiFi/BLE
-external Flash
-maybe an sd card
-a secondary mcu to switch between a PC serial terminal or an onscreen LCD terminal.
-this display or one at a higher resolution
-a mini keyboard (I will determine what goes on the keyboard soon.)
-stm32f4xx main mcu (I have never used these before, but they look like the best for uPython.)

I ask here for anyone who knows what I should include on my board and what I should do to allow this device to perform at its best. I hope to power it by AAA batteries or button cells. The hardware will be open source. No claims to own uPython will be made. I want to make this about the size of a TI-30X IIs calculator. This project will likely be a long time in development.

[jimmo]

-WiFi/BLE
-external Flash
-maybe an sd card

For these first three, probably worth taking a look at the Pyboard D which is designed to be used as a module in larger boards via the mezzanine (WBUS) connectors. That way the above three items are just taken care of.

Also MicroPython already includes WiFi & BLE drivers for that Broadcom (now Cypress) chip, which saves you having to think about how to handle any of that.

Maybe on a future revision you can do it all from scratch but this would be a great way to build a prototype.

It's an STM32F7 but that's probably good anyway.

-a secondary mcu to switch between a PC serial terminal or an onscreen LCD terminal.

Not sure why it needs to be a secondary MCU -- the STM32F4 (and F7) have more than enough UARTs and with APIs like dupterm you can manage all this on the main micro.

[AwesomeCronk]

Okay, then. I was thinking the secondary MCU would handle the graphics as well. If the STM will do that, then by all means I'll go that route. Would it be possible to have a physical switch to flip between graphics mode and console mode? The idea is that a custom pygame-style graphics library could be added to the firmware distribution, allowing me to display on the screen. I would then be able to change between the console and the graphics window, as a workaround for not having a windowing system.

[AwesomeCronk]

Alright, I need to prioritize. First step is getting the keyboard sorted out. Then I will need to get the hardware set up. Than, once everything works, maybe I can do graphics.