NRF52832 (Nordic Thingy52 ) SD CARD problem

Hi,

I am trying to use a FS on SD Card with a NRF52. I compiled the image for the nrf52dk target , taking care to add the filesystem feature to it. this works (I have access to function E.connectSDCard() ).
I am using software SPI (var ThingySpi=new SPI();):
MOSI=D4
MISO=D3
SCK=D2
CS=D11

This doesn't work. CS pin correctly goes down when a communication occurs, SCK line sends multiple pulses (8 at a time) but nothing goes out of MOSI. By calling getPinMode it tells me that the pin is "output", that seems to be correct for a software SPI.
By calling digitalWrite() I can correctly put it high or low. edges are very clean (verified with a scope).
Then I tried to call ThingySpi.write(0xFF) and this time, the data correctly went out of MOSI.

My question is then: Can the SD/FS module run on top of software SPI?

ps: The same setup on another board (by example my STM32F4DISCOVERY with a custom build with added filesystem feature) works perfectly.