5 RT-thread 两种方式读取到W25Q16的ID，高低位是反过来的

发布于 2021-11-10 14:48:55 浏览：1322 订阅该版

```c
#include "W25Q16.h"

struct rt_spi_device *spi_dev_w25q;

void W25Q16_thread()
{
    __HAL_RCC_GPIOA_CLK_ENABLE();
    rt_hw_spi_device_attach("spi1", W25Q_SPI_DEVICE_NAME, GPIOA, GPIO_PIN_2);

spi_dev_w25q = (struct rt_spi_device *)rt_device_find(W25Q_SPI_DEVICE_NAME);
    if (!spi_dev_w25q)
    {
        rt_kprintf("spi sample run failed! can't find %s device!\r\n", W25Q_SPI_DEVICE_NAME);
    }
    else
    {
        rt_kprintf("spi sample run success\r\n");
        {
            struct rt_spi_configuration cfg;
            cfg.data_width = 8;
            cfg.mode = RT_SPI_MODE_0 | RT_SPI_MSB; /* SPI Compatible: Mode 0 and Mode 3 */
            cfg.max_hz = 50 * 1000 * 1000; /* 50M */
            rt_spi_configure(spi_dev_w25q, &cfg);
        }

rt_uint8_t w25x_read_id = 0x90;
        rt_uint8_t id1[5] = {0};

rt_uint8_t w25x_read_id2[4] = {0x90,0x00,0x00,0x00};
        rt_uint8_t id2[2] = {0};

rt_spi_send_then_recv(spi_dev_w25q, &w25x_read_id, 1, id1, 5);
        rt_kprintf("w25q ID is:%x%x\r\n", id1[3], id1[4]);

rt_spi_send_then_recv(spi_dev_w25q, w25x_read_id2, 4, id2, 2);
        rt_kprintf("w25q ID is:%x%x\r\n", id2[0], id2[1]);
    }

}

```
![QQ图片20211110144833.png](https://oss-club.rt-thread.org/uploads/20211110/fc0676338b8b626eb80236465bf4f41e.png)

3 个回答

出出啊 2021-11-10

恃人不如自恃，人之为己者不如己之自为也

Yuanq 2021-11-10

这家伙很懒，什么也没写！

出出啊 2021-11-10

恃人不如自恃，人之为己者不如己之自为也

出出啊 2021-11-11

恃人不如自恃，人之为己者不如己之自为也

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追加回复

李肯陪你玩赚嵌入式 认证专家 2021-11-10

2022年度和2023年度RT-Thread社区优秀开源布道师，COC深圳城市开发者社区主理人，专注于嵌入式物联网的架构设计

NoneKnowsMe 2024-11-06

这家伙很懒，什么也没写！

遇到了和题主一样的现象：

```c
struct rt_spi_device *spi_dev_w25q;
char name[RT_NAME_MAX]="spi3_0";
rt_uint8_t w25q_read_id1[4] = {0x90,0x00,0x00,0x00};// 指令码0x90表示芯片的ID，先读Manufacturer ID后读Device ID
rt_uint8_t w25q_read_id2[4] = {0x90,0x00,0x00,0x01};// 指令码0x90表示芯片的ID，先读Device ID后读Manufacturer ID
rt_uint8_t id[6] = {0};

```

```c
/* 方式1：使用 rt_spi_send_then_recv()发送命令读取ID */
rt_spi_send_then_recv(spi_dev_w25q, &w25q_read_id1, 4, id, 5);
rt_kprintf("use rt_spi_send_then_recv() read w25q ID is:%x%x%x%x%x%x\n", id[0], id[1], id[2], id[3], id[4], id[5]);

/* 方式2：使用 rt_spi_transfer_message()发送命令读取ID */
struct rt_spi_message msg1, msg2;

msg1.send_buf   = &w25q_read_id2;
msg1.recv_buf   = RT_NULL;
msg1.length     = 4;
msg1.cs_take    = 1;
msg1.cs_release = 0;
msg1.next       = &msg2;

msg2.send_buf   = RT_NULL;
msg2.recv_buf   = id;
msg2.length     = 5;
msg2.cs_take    = 0;
msg2.cs_release = 1;
msg2.next       = RT_NULL;

rt_spi_transfer_message(spi_dev_w25q, &msg1);
rt_kprintf("use rt_spi_transfer_message() read w25q ID is:%x%x%x%x%x%x\n", id[0], id[1], id[2], id[3], id[4], id[5]);

```
执行结果：

```shell
use rt_spi_send_then_recv() read w25q ID is:ef17ef17ef0
use rt_spi_transfer_message() read w25q ID is:17ef17ef170
```
截图：

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20241106/3b8005346a1bf3b476116bf0f7460673.png)

我能理解顺序不同是因为w25q_read_id1和w25q_read_id2的内容最后一个字节0x00和0x01的差别导致的。
不能理解的点：
1、为什么ef和17会反复出现
2、如果把指令码都改成：
```c
rt_uint8_t w25q_read_id1[4] = {0x90,0x00,0x00,0x00};// 指令码0x90表示芯片的ID，先读Manufacturer ID后读Device ID
rt_uint8_t w25q_read_id2[4] = {0x90,0x00,0x00,0x00};// 指令码0x90表示芯片的ID，先读Device ID后读Manufacturer ID
```
但是发送命令时只发1个字节（0x90），读到的结果就是00 00 00 17 ef 00。
发送命令时发4个字节（0x90,0x00,0x00,0x00），读到的结果就是ef 17 ef 17 ef 00。

```c
rt_spi_send_then_recv(spi_dev_w25q, &w25q_read_id1, 1, id, 5);
rt_kprintf("use rt_spi_send_then_recv() read w25q ID is:%x%x%x%x%x%x\n", id[0], id[1], id[2], id[3], id[4], id[5]);
// ...
struct rt_spi_message msg1, msg2;

msg1.send_buf   = &w25q_read_id2;
msg1.recv_buf   = RT_NULL;
msg1.length     = 4;
msg1.cs_take    = 1;
msg1.cs_release = 0;
msg1.next       = &msg2;

msg2.send_buf   = RT_NULL;
msg2.recv_buf   = id;
msg2.length     = 5;
msg2.cs_take    = 0;
msg2.cs_release = 1;
msg2.next       = RT_NULL;

rt_spi_transfer_message(spi_dev_w25q, &msg1);
rt_kprintf("use rt_spi_transfer_message() read w25q ID is:%x%x%x%x%x%x\n", id[0], id[1], id[2], id[3], id[4], id[5]);
```
测试结果：

```shell
use rt_spi_send_then_recv() read w25q ID is:00017ef0
use rt_spi_transfer_message() read w25q ID is:ef17ef17ef0
```
截图：

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20241106/721faa8ebf2252ea30c13a9709d7daf7.png)