AnsweredAssumed Answered

AD9957 SPI problem

Question asked by Alex_777 on Nov 16, 2015
Latest reply on Nov 30, 2015 by Alex_777

Hello, I can not write and read any registers in AD9957.

I do not have any  signal on AD9957 RF output (In single mode).


I am using a crystal at the REF_CLK input, the resonant frequency is 25 MHz.

I have 6.25MHz on SYNC_CLK pin and  25MHz on REFCLK_OUT pin.

I am do the next:

1) Power up device and apply REF CLK source.

2) Issue master reset to place the device in default state.

3) Configure registers.

4) Send I/O_UPDATE


I have the next configuration:

1) Chip select pin  I make allways '0'.

2) MSB First

3) SDIO Input only


Register section:

uint8_t CFR1[5]= {0x01, 0x00, 0x00, 0x00};

uint8_t CFR2[5]= {0x00, 0x40, 0x08, 0x20};

uint8_t CFR3[5]= {0x13, 0x20, 0x41, 0x1B};

uint8_t PROF_0[9]= {0x08, 0xB5, 0x00, 0x00, 0x00, 0x61, 0x17, 0x22};



For example, the register (CFR3) read operation:


1) Set  R/W—Bit 7 of the instruction byte to "1" + number of register - 0x02 (CFR3)

2) Send this byte on SPI and then 4 bytes 0x00.


But I have allways 0xFFFFFFFF.


On this picture I send  0b100000010




On this picture we have  read operation is fully.




Tell me please, where is my mistake?

I am hope for your understanding. Thanks.