5 SPI通信时，PIN设备驱动使用异常，出现毛刺信号？

发布于 2021-07-29 09:01:17 浏览：1816 订阅该版

1、使用rt-thread studio开发SPI与FPGA通信功能，发现FPGA读取数据偶尔会出现异常。
正常时的波形如下图所示：
![CS正常数据.PNG](https://oss-club.rt-thread.org/uploads/20210729/efca5a9e34a5d5dc6d5aefef2f3770ad.png)

异常时CS出现毛刺
波形如下图所示：![CS异常数据.PNG](https://oss-club.rt-thread.org/uploads/20210729/ffe84556060ffdc01973f3518254362c.png.webp)

有两个疑问：
1、使用PIN驱动会产生毛刺信号，不使用PIN驱动不会产生毛刺信号
2、CS拉低以后，很久才会开始发送数据。数据发送完成后，需要很久才会拉高CS

实验代码如下：

```c
#include <rtthread.h>
#include <rtdevice.h>
#include <drv_spi.h>
#include "drv_common.h"

#define LOG_TAG "SPI"
#define LOG_LVL LOG_LVL_DBG
#include <ulog.h>

#define TEST_DEVICE_NAME "spi2"

static struct rt_spi_device *spi_dev_com;

rt_uint8_t sendbuff[26];
rt_uint8_t rebuff[26];

void test_spi(int arg,char **argv)
{
    rt_err_t ret;
    rt_size_t len;
    static rt_uint8_t aa = 0;
    if(aa == 0)
    {
        aa  = 1;
        __HAL_RCC_GPIOI_CLK_ENABLE();
        rt_hw_spi_device_attach("spi2", "spi20", GPIOI, GPIO_PIN_0);

LOG_I("This is spi test ");

for(rt_uint8_t i=0;i<26;i++)
        {
            sendbuff[i] = 0x10+i;
        }

spi_dev_com = (struct rt_spi_device *)rt_device_find("spi20");
        if(!spi_dev_com)
        {
            LOG_E("not find spi device");
            return;
        }
        else {
            struct rt_spi_configuration cfg;
            cfg.data_width = 8;
            cfg.max_hz = 10*1000*1000;
            cfg.mode = RT_SPI_MASTER | RT_SPI_MODE_3 | RT_SPI_MSB;

ret = rt_spi_configure(spi_dev_com, &cfg);
            if(ret != RT_EOK)
            {
                LOG_E("Config spi failed");
                return;
            }
        }
    }
    len = rt_spi_transfer(spi_dev_com, sendbuff, rebuff, 26);
    if(len != 26)
    {
        LOG_E("spi write erro");
    }
    else
    {
        for(int i=0;i<26;i++)
            rt_kprintf("%4d ",rebuff[i]);
    }
    rt_kprintf("\r\n");

}

MSH_CMD_EXPORT(test_spi,test_spi
```