SPI Master Switch CS

This sample demonstrates how SPI1 dynamically switches CS signals. In this example, SPI is configured as a master and the direction is full-duplex. The chip writes some data to SPI slave device0, then switches to slave device1 and device2 and sends data to them.

Requirements

For hardware requirements, please refer to the Requirements.

Wiring

Connect P1_3 (master CS0) to CS of SPI slave device 0, connect P1_4 (master CS1) to CS of SPI slave device 1, connect P1_5 (master CS2) to CS of SPI slave device 2, connect P1_0 (master SCK) to SCK of SPI slave device 0/1/2, connect P1_1 (master MISO) to MISO of SPI slave device 0/1/2, and connect P1_2 (master MOSI) to MOSI of SPI slave device 0/1/2.

The hardware connection of SPI sample code is shown in the figure below.

../../../_images/SPI_Demo_4_1_Hardware_Connection_Diagram.png — SPI Sample Code Hardware Connection Diagram

Configurations

The following macros can be configured to modify pin definitions.
- #define PIN_SPI1_SCK P1_0
- #define PIN_SPI1_MOSI P1_1
- #define PIN_SPI1_MISO P1_2
- #define PIN_SPI1_CS0 P1_3
- #define PIN_SPI1_CS1 P1_4
- #define PIN_SPI1_CS2 P1_5
The entry function is as follows, call this function in main() to run this sample code. For more details, please refer to the Initialization.
```
spi_switchcs_demo();
```

Building and Downloading

For building and downloading, please refer to the Building and Downloading.

Experimental Verification

Press the Reset button on the EVB.
The data in array SPI_WriteBuf is sent to SPI slave device 0.
Then the data in array SPI_WriteBuf is sent to SPI slave device 1.
Then the data in array SPI_WriteBuf is sent to SPI slave device 2.

Code Overview

Source Code Directory

For project directory, please refer to Source Code Directory.
Source code directory: sdk\src\sample\io_demo\spi\dynamic_switch_cs\spi_switchcs_demo.c .

Initialization Flow

The initialization flow for peripherals can refer to Initialization Flow.

SPI initialization flow is shown in the following figure.

../../../_images/SPI_Initialization_Flow_Chart.png — SPI Initialization Flow Chart

Call Pad_Config() and Pinmux_Config() to initialize the pins.

static void board_spi_init(void)
{
   Pinmux_Config(PIN_SPI1_SCK, SPI1_CLK_MASTER);
   Pinmux_Config(PIN_SPI1_MOSI, SPI1_MO_MASTER);
   Pinmux_Config(PIN_SPI1_MISO, SPI1_MI_MASTER);
   Pinmux_Config(PIN_SPI1_CS0, SPI1_SS_N_0_MASTER);
   Pinmux_Config(PIN_SPI1_CS1, SPI1_SS_N_1_MASTER);
   Pinmux_Config(PIN_SPI1_CS2, SPI1_SS_N_2_MASTER);

   Pad_Config(PIN_SPI1_SCK, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE,
               PAD_OUT_HIGH);
   Pad_Config(PIN_SPI1_MOSI, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE,
               PAD_OUT_HIGH);
   Pad_Config(PIN_SPI1_MISO, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE,
               PAD_OUT_HIGH);
   Pad_Config(PIN_SPI1_CS0, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE,
               PAD_OUT_HIGH);
   Pad_Config(PIN_SPI1_CS1, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE,
               PAD_OUT_HIGH);
   Pad_Config(PIN_SPI1_CS2, PAD_PINMUX_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_ENABLE,
               PAD_OUT_HIGH);
}

Call RCC_PeriphClockCmd() to enable the SPI clock and function.

Initialize the SPI peripheral:

Define the SPI_InitTypeDef type SPI_InitStructure, and call SPI_StructInit() to pre-fill SPI_InitStructure with default values.
Modify the SPI_InitStructure parameters as needed. The SPI initialization parameter configuration is shown in the table below.
Call SPI_Init() to initialize the SPI peripheral.

SPI Initialization Parameters
SPI Hardware Parameters	Setting in the `SPI_InitStructure`	SPI
Direction	`SPI_InitTypeDef::SPI_Direction`	`SPI_Direction_FullDuplex`
Device Role (SPI Master or SPI Slave)	`SPI_InitTypeDef::SPI_Mode`	`SPI_Mode_Master`
Data Frame Size	`SPI_InitTypeDef::SPI_DataSize`	`SPI_DataSize_8b`
Clock Polarity	`SPI_InitTypeDef::SPI_CPOL`	`SPI_CPOL_High`
Clock Phase	`SPI_InitTypeDef::SPI_CPHA`	`SPI_CPHA_2Edge`
Clock Div	`SPI_InitTypeDef::SPI_BaudRatePrescaler`	100
Frame Format	`SPI_InitTypeDef::SPI_FrameFormat`	`SPI_Frame_Motorola`

Call SPI_Cmd() to enable SPI.

Functional Implementation

Master Send Data by Polling

Call SPI_SendBuffer() to send the data in SPI_WriteBuf to the slave.
Call SPI_GetFlagState() to check SPI_FLAG_TFE and SPI_FLAG_BUSY flag state, and wait for the SPI data transfer to complete.
Call SPI_SetCSNumber() to switch slave device.

uint8_t SPI_WriteBuf[3] = {0x01, 0x02, 0x03};

SPI_SendBuffer(SPI1, SPI_WriteBuf, 3);

/* wait TX FIFO empty */
while (SPI_GetFlagState(SPI1, SPI_FLAG_TFE) == RESET);
while (SPI_GetFlagState(SPI1, SPI_FLAG_BUSY));

SPI_SetCSNumber(SPI1, 1);