AXI quad SPI没有输出（已解决）

在使用ZYNQ的AXI quad SPI时遇到以下问题：
使用loopback可以成功，但是使用示波器测量引脚却没有输出。

---

问题描述：

最近在用ZYNQ的AXI quad SPI拓展接口，却遇到了这个问题：
添加AXI quad SPI核，编译完毕后。使用官方例程，loopback模式可以跑通，但是正常输出模式无法工作，且用示波器测试引脚输出没有波形。

IP核AXI quad SPI的设置如下：

程序为AXI quad SPI官方的 xspi_polled_example：

/***************************** Include Files *********************************/#include "xparameters.h" /* XPAR parameters */ #include "xspi.h" /* SPI device driver */ #include "xspi_l.h" #include "xil_printf.h"/************************** Constant Definitions *****************************//** The following constants map to the XPAR parameters created in the* xparameters.h file. They are defined here such that a user can easily* change all the needed parameters in one place.*/ #define SPI_DEVICE_ID XPAR_SPI_0_DEVICE_ID/** This is the size of the buffer to be transmitted/received in this example.*/ #define BUFFER_SIZE 12/**************************** Type Definitions *******************************//** The following data type is used to send and receive data on the SPI* interface.*/ typedef u8 DataBuffer[BUFFER_SIZE];/***************** Macros (Inline Functions) Definitions *********************//************************** Function Prototypes ******************************/int SpiPolledExample(XSpi *SpiInstancePtr, u16 SpiDeviceId);/************************** Variable Definitions *****************************//** The instances to support the device drivers are global such that the* are initialized to zero each time the program runs.*/ static XSpi SpiInstance; /* The instance of the SPI device *//** The following variables are used to read and write to the Spi device, they* are global to avoid having large buffers on the stack.*/ u8 ReadBuffer[BUFFER_SIZE]; u8 WriteBuffer[BUFFER_SIZE];/*****************************************************************************/ /** * * Main function to call the Spi Polled example. * * @param None * * @return XST_SUCCESS if successful, otherwise XST_FAILURE. * * @note None * ******************************************************************************/ int main(void) {int Status;/** Run the Spi Polled example.*/Status = SpiPolledExample(&SpiInstance, SPI_DEVICE_ID);if (Status != XST_SUCCESS) {xil_printf("Spi polled Example Failed\r\n");return XST_FAILURE;}xil_printf("Successfully ran Spi polled Example\r\n");return XST_SUCCESS; }/*****************************************************************************/ /** * * This function does a minimal test on the Spi device and driver as a * design example. The purpose of this function is to illustrate how to use * the XSpi component using the polled mode. * * This function sends data and expects to receive the same data. * * * @param SpiInstancePtr is a pointer to the instance of Spi component. * @param SpiDeviceId is the Device ID of the Spi Device and is the * XPAR_<SPI_instance>_DEVICE_ID value from xparameters.h. * * @return XST_SUCCESS if successful, otherwise XST_FAILURE. * * @note * * This function contains an infinite loop such that if the Spi device is not * working it may never return. * ******************************************************************************/ int SpiPolledExample(XSpi *SpiInstancePtr, u16 SpiDeviceId) {int Status;u32 Count;u8 Test;XSpi_Config *ConfigPtr; /* Pointer to Configuration data *//** Initialize the SPI driver so that it is ready to use.*/ConfigPtr = XSpi_LookupConfig(SpiDeviceId);if (ConfigPtr == NULL) {return XST_DEVICE_NOT_FOUND;}Status = XSpi_CfgInitialize(SpiInstancePtr, ConfigPtr,ConfigPtr->BaseAddress);if (Status != XST_SUCCESS) {return XST_FAILURE;}/** Perform a self-test to ensure that the hardware was built correctly.*/Status = XSpi_SelfTest(SpiInstancePtr);if (Status != XST_SUCCESS) {return XST_FAILURE;}/** Run loopback test only in case of standard SPI mode.*/if (SpiInstancePtr->SpiMode != XSP_STANDARD_MODE) {return XST_SUCCESS;}/** Set the Spi device as a master and in loopback mode.*/Status = XSpi_SetOptions(SpiInstancePtr, XSP_MASTER_OPTION |XSP_LOOPBACK_OPTION);if (Status != XST_SUCCESS) {return XST_FAILURE;}/** Start the SPI driver so that the device is enabled.*/XSpi_Start(SpiInstancePtr);/** Disable Global interrupt to use polled mode operation*/XSpi_IntrGlobalDisable(SpiInstancePtr);/** Initialize the write buffer with pattern to write, initialize the* read buffer to zero so it can be verified after the read, the* Test value that is added to the unique value allows the value to be* changed in a debug environment.*/Test = 0x10;for (Count = 0; Count < BUFFER_SIZE; Count++) {WriteBuffer[Count] = (u8)(Count + Test);ReadBuffer[Count] = 0;}/** Transmit the data.*/XSpi_Transfer(SpiInstancePtr, WriteBuffer, ReadBuffer, BUFFER_SIZE);/** Compare the data received with the data that was transmitted.*/for (Count = 0; Count < BUFFER_SIZE; Count++) {if (WriteBuffer[Count] != ReadBuffer[Count]) {return XST_FAILURE;}}return XST_SUCCESS; }

编译下载之后，串口提示运行成功，

将loopback模式关闭，设置为禁止loopback，CPOL = 1 CPHA = 1。

Status = XSpi_SetOptions(SpiInstancePtr, XSP_MASTER_OPTION |XSP_LOOPBACK_OPTION); //修改为禁止loopback，CPOL = 1 CPHA = 1 Status = XSpi_SetOptions(SpiInstancePtr, XSP_MASTER_OPTION |XSP_CLK_PHASE_1_OPTION | XSP_CLK_ACTIVE_LOW_OPTION);

然后，把mosi引脚和miso引脚短接。然后编译、下载，提示运行错误

使用示波器测量SCK、mosi引脚，发现没有波形。

---

原因分析：

然后在Xilinx的论坛上发现也有人反馈这个问题，最后原因好像是：
因为SS0的引脚一直输出是高电平引起的，我后来将程序修改为持续向SPI发送数据，发现确实是SS0引脚一直是高电平（刚烧写完程序，SS0也会持续一段时间的高电平）。
个人认为可能是SPI自动选择从机编号发生了问题。

---

解决方案：

参考论坛中的解决方法，具体解决方案：
将从机选择设置为手动选择(XSP_MANUAL_SSELECT_OPTION)

Status = XSpi_SetOptions(SpiInstancePtr, XSP_MASTER_OPTION |XSP_CLK_PHASE_1_OPTION | XSP_CLK_ACTIVE_LOW_OPTION | XSP_MANUAL_SSELECT_OPTION);

然后再在SPI禁止中断语句之后，加入选择从机编号的语句。（1号从机的选择引脚就是SS0）

/** Disable Global interrupt to use polled mode operation*/XSpi_IntrGlobalDisable(SpiInstancePtr);XSpi_SetSlaveSelect(SpiInstancePtr, 0x01); //选择从机编号

经过以上修改后，再次编译烧写，程序运行正确。

与50位技术专家面对面20年技术见证，附赠技术全景图

总结

以上是生活随笔为你收集整理的AXI quad SPI没有输出的全部内容，希望文章能够帮你解决所遇到的问题。

如果觉得生活随笔网站内容还不错，欢迎将生活随笔推荐给好友。