can't get fatfs work on sdk 15.3

[zzzh]

Hello,

I was trying to make fatfs example work on my nrf52_pca10040 board, but it always fail to init (<info> app: Disk initialization failed.)

I'm using a 4GB sd card, seems it's supposed to be formatted by 512 bytes block, how to do that? ( it's in 64kB block now, formatted on windows, which don't have another option for FAT file system.)

[zzzh]

**************************************************************************************************

// <o> NRF_SPI_DRV_MISO_PULLUP_CFG - MISO PIN pull-up configuration.

// <0=> NRF_GPIO_PIN_NOPULL
// <1=> NRF_GPIO_PIN_PULLDOWN
// <3=> NRF_GPIO_PIN_PULLUP

#ifndef NRF_SPI_DRV_MISO_PULLUP_CFG
#define NRF_SPI_DRV_MISO_PULLUP_CFG 1
#endif

***************************************************************************************************

I noticed some talk about MISO PIN pull-up configuration, it's set to NRF_GPIO_PIN_PULLDOWN in sdk 15.3, as listed above.

I tried to change it to NOPULL, still don't work