[Gnuk-users] Gnuk on a faster MCU

[NIIBE Yutaka]

Hello,

Another thing you can try for RSA is that...

If it has more RAM, you can change the line in
gnuk/polarssl/library/bignum.c:

    size_t wsize = ( i > 1024 ) ? 4 : /* Because of not enough memory.  */

to, say, 6 (or 5 if not more).


If still not fast enough, I'd suggest to find a chip with 120MHz.

Yesterday, I checked NXP and found Kinetis/Freescale K22F @ 120MHz.

https://www.nxp.com/products/microcontrollers-and-processors/arm-based-processors-and-mcus/kinetis-cortex-m-mcus/k-series-performance-m4/k2x-usb/kinetis-k22-120-mhz-cost-effective-full-speed-usb-microcontrollers-mcus-based-on-arm-cortex-m4-core:K22_120

MK22FN128CAH12 - Kinetis K 32-bit MCU, ARM Cortex-M4 core, 128KB Flash, 120MHz, USB, WLCSP 64

MK22FN256CAH12 - Kinetis K 32-bit MCU, ARM Cortex-M4 core, 256KB Flash, 120MHz, USB, WLCSP 64
MK22FN256CAP12 - Kinetis K 32-bit, ARM Cortex-M4 core, 256KB Flash, 120MHz, USB, 80WLCSP
MK22FN256VMP12 - Kinetis K22: 120MHz Cortex-M4F Performance MCU, 256KB Flash, 48KB SRAM, Full-Speed USB, 64-MAPBGA

MK22FN512CAP12 - Kinetis K 32-bit MCU, ARM Cortex-M4 core, 512KB Flash, 120MHz, USB, WLCSP 80
MK22FN512CBP12 - Kinetis K 32-bit, ARM Cortex-M4 core, 512KB Flash, 120MHz, USB, Thin 80WLCSP
MK22FN512VMP12 - Kinetis K22: 120MHz Cortex-M4F Performance MCU, 512KB Flash, 128KB SRAM, Full-Speed USB, 64-MAPBGA

It includes a regulator (from USB Vbus +5V) and can run without crystal
(no capacitive sensor, just like the chip of FS-BB48).

0.5mm pitch MAPBGA is easier for PCB design/manufacturing/assembly.  And
I think availability of the part is better (than other WLCSP ones).  But
thickness is 1.23mm.  I think that it's not acceptable for the PCB
design which uses bottom layer to put a MCU (like the design of Tomu).

For thin WLCSP 80, thickness is 0.34mm.  Since pitch is 0.4mm, it
requires more for PCB design/manufacturing/assembly.

For me, WLCSP would be too challenging, for now.  I would consider
something like FS-BB120.
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