How to write regs?

I’m tring to use DW1000, and used the example codes.Now I can read 0xDECA0130 and 0xDECA,
but when i try to write regs, I found the regs never changed.I’v see the scope, can’t find any problem.
Any suggestion?

It’s the write timing. I use GPIO simulate SPI, very slow speed.

dwt_write32bitoffsetreg(USR_SFD_ID, 0, 0x10403F00);
uint32 usr_sfd = dwt_read32bitoffsetreg(USR_SFD_ID, 0);

usr_sfd is always 0x98FFFC10