I can not receive the data from the peripherical slave device(MAX6675)

Question

Hi, I write a code for the max6657 temperture via modifying the SPI MASTER Example. The function for reading max6675 via SPI is shown as follow

uint16_t readCelsius(void){
uint16_t flag;
uint16_t temp;
uint16_t tempc;
uint32_t spi_rw_err_code;

APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, NULL, 0, m_rx_buf, m_length));

temp=m_rx_buf[0]<<8;

flag=temp&0x04;
	if (flag){
	  return 8888;}

    temp>>=3;
    tempc=temp*.25;  	
    SEGGER_RTT_printf(0,"TEMP*4=%6.2f\n",tempc);
nrf_gpio_pin_set(SPI_CS_PIN);		
return tempc; }

but i can the the data 0x0000。

In order to makesure that the SPI is working correct, I use the Logic Analyzer to measure the pattern of the SPI sigal which is shown as follow: image description

I think that the spi is work well，but it read the data 0x0000!

I review the API function nrf_drv_spi_transfer() and spi_xfer() in the file "nrf_drv_psi.c" I find that only the function "nrf_spi_txd_set" which is a function for writing data to the SPI transmitter register is used. And the function " nrf_spi_rxd_get() " for reading data from the SPI receiver register is never been used. I guess that the function "nrf_drv_spi_transfer()" is "send" only, and I can get the data 0x0000 from the temperature sensor. Is my guess correctly?!

If my guess is wrong, how can I read it correctly? Thank for your suggestion。

By the way The sensor is work well when it is connected to the STM32 board.
The signal read via Logic Analyzer is image description Except the data length per transfer(8bit in STM32, 16bit in nRF51822), the other configureation of SPI in nRF51288 board is the same as tho one in STM32 board.

Thanks for your review and suggestion. Best Wishes