Hey!
About a week ago I bought a FEZ Cerebus.
I’m very excited about it, but now I want to create a my own board. It should be very small and consume little power.
I have already gained experience with DFU, TinyBooter and ST-Link.
Now I found the chip STM32F411CC (WLCSP49) and wonder whether the .NET MF can be installed on this processor, without recompiling the MF…
I hope you can help me.
Greetings from Switzerland!
@ misaro - You will need to go one step higher and use STM32F411CE
You will need to recompile the the firmware to suit the package - but thats not an issue…
@ Justin - Thanks! STM32F411CE is also good.
What do you mean by “to suit the package”? Just some configuration changes?
That would be easy… hehe
@ misaro - I am interested in this process. Please keep us posted on your progress.
Thank you.
@ misaro - you will need to change a few files to suite the package - ie ram and flash size and pin mappings etc.
Since you are running with so little resources you will also need to compile the firmware with MDK or similar as i am fairly sure GCC will produce a binary which is too large.
So in essence you will need to change the following files:
platform_selector.h
IO_Init.cpp
scatterfile_bootloader_mdk.xml
scatterfile_tinyclr_mdk.xml
STM32F4_BlConfig.cpp
TinyBooterEntry.cpp
Word of caution - unless your are strong in the art of PCB Fu you will struggle to use the WLCSP-49 package as you are talking about 0.4mm ball pitch which will require filled VIP’s etc which will require expensive PCB’s. Also you will need to place some 0.1uF’s on the back side of the PCB which although not difficult will require more manufacture steps.
You maybe a PCB Ninja with a pocket full of cash so you can happily ignore the above 
Attached is an image of the 64 pint Cerb STM, the 7mm QFN that i like using and the WLCSP-49 package - you can see that the 0.2mm hole via doesn’t fit in between balls hence the need from VIP’s
If you are the mad scientist and do go marching off into the sunset and create a PCB running a WLCSP-49 please document the process as that would be very cool and i would happily supply a binary for it
@ Justin - how many layers would it take to break out those bga pins? 2? 4?
@ Mr. John Smith - 4 layers at a stretch but 6 is more realistic.
An alternative would be to use the UFQFPN-48 package?
Although it’s over double the size of the WLCSP-49 package it is still smaller than the LQFP package at 7 x 7mm.
Have fun with with your PCB design whatever package you choose
@ Justin - Hehe thanks. Yep, WLCSP49 (15.47 mil / 0.4mm pitch) is fu** small! But that’s not the problem here, designing PCB is part of my job 
And the best part: My colleague works at a PCB manufacturer. They can produce their own boards, even for private purpose.
Now i try rebuilding the framework…
Now thats just teasing… :
If you want a binary for the 411 just let me know.