S2LP : Impossible to write registers

[VCano.1]

We've been using the S2LP in several designs, and we are happy with it. I'm working on a new PCB. However, since two days, I'm stuck with bug I have no more ideas how to debug it.

I can read the registers successfully, but whenever I try to modify one of them, the value is not updated.

I've made captures with our logic analyzer and everything seems perfectly normal. The logic analyzer capture is attached. It can be opened with this free software : https://www.ikalogic.com/scanastudio/

I have 4 boards and all of them have the same problem...

Here is my test :

s2lp: Found S2LP!
s2lp: chip version = 193
s2lp: status =
XO_ON = 1
TX_FIFO_FULL = 0
RX_FIFO_EMPTY = 1
RCCAL_OK = 1
MC_STATE = READY
ERROR_LOCK = 0
ANT_SELECT = 0
s2lp: writing 0x37 into 0x75 reg
s2lp: Reading reg 0x75 = 0x17

I try to write 0x37 in 0x75 register, but then I read back 0x17 (the default value). I've tested all sort of things, but no matter what I do, I can't write the registers.

What can prevent the S2LP registers to be written?

Please help, I have no more ideas...

Victor

[VCano.1]

Problem is solved, it was the SPI frame generated by the master which was malformed, which unfortunately was tricky to detect because the read command was working. 

S2LP is now sending data !