12 Configure the AXI SPI

The AXI SPI instance in TI AFE SPI IP is used in Standard Mode.

Peripherals select 0 and select 1 are used as chip selects for AFE and LMK clocking device, respectively

SCL frequency is hard coded to 10 MHz within TI IP

Key commands for SPI initialization and usage in Vitis are as explained below:

1. XSpi_Config *ConfigPtr;

   Initialize a pointer (ConfigPtr).

2. ConfigPtr = XSpi_LookupConfig(XPAR_AXI_QUAD_SPI_0_DEVICE_ID);

   Refer ‘Xparameters.h’ to find the correct AXI QUAD SPI DEVICE ID.

3. XSpi_CfgInitialize(&Spidev, ConfigPtr, ConfigPtr->BaseAddress);

   Initialize a new instance of SPI (Spidev).

4. XSpi_SetOptions(&Spidev, XSP_MASTER_OPTION);

   Set the Spidev instance to be in Controller mode.

5. XSpi_Start(&Spidev);
6. XSpi_SetSlaveSelect(&Spidev, 1);

   Select Peripheral: AFE.

7. XSpi_SetSlaveSelect(&Spidev, 2);

   Select Peripheral: LMK.

8. XSpi_Transfer(&Spidev, WrBufdev, RdBufdev, 3);

   Second argument WrBufdev is an array with 3 bytes (24-bit data to be transmitted on SPI).

   Third argument RdBufdev is an array with 3 bytes, the last byte has the SPI read value.

   Fourth argument is number of bytes to be transmitted/received...3 in our case.

The D23 is the MSB bit of the 24-bit data because the D23 indicates whether it is a Read or a Write SPI operation:

• If D23 is set to 1, then it is a read operation and RdBufdev[2] stores the read back address contents
• If D23 is set to 0, then it is a write operation and RdBufdev[2] has no significance