SPI 代码不稳定性 - RPi 上的 Raspbian (Debian) Linux

Question

我正在尝试让我的软件通过 Raspbian (Debian) Linux 从 Raspberry Pi 3 读写 CAT25512 EEPROM。在写入存储器之前，必须使用命令 0x06 设置写使能锁存器 (WEL)。本次写入成功。然后使用读取状态寄存器命令 0x05 进行检查，该命令也成功。然后写入、读取和连续状态读取命令没有响应和/或失败。

我尝试添加一些延迟来等待硬件。我也多次重构代码。

我提前为完整的文件道歉，但我不确定问题出在哪里。

#include <stdint.h>
    #include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/spi/spidev.h>
#include <string>
#include <cstring>

#define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
#define WAIT_FOR_EEPROM(a) do { for (int z=0; z<0x3FFF; z++); } while (eepromBusy((a) != 0x02));

const char *device = "/dev/spidev0.0";

uint8_t  mode=SPI_MODE_0;
uint8_t  bits=8;
uint32_t baud=500000;

uint8_t buffer[4] = {0};

int transfer(int spi_file, uint8_t* buffer, int length); // Prototype

int eepromBusy(int spi_file) {
        buffer[0] = 0x05;
        buffer[1] = 0x00;

        transfer(spi_file, buffer, 2);
        return (buffer[1]);
}

int main() {
        int fd = open(device,O_RDWR);
        if (fd < 0) printf("can't open device");

        int ret;
        ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);
        if (ret == -1) printf("can't set spi mode");

        ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);
        if (ret == -1) printf("can't set bits!");

        ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &baud);
        if (ret == -1) printf("can't set speed!");

        ret = ioctl(fd, SPI_IOC_RD_MODE, &mode);
        if (ret == -1) printf("can't set spi mode");

        ret = ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits);
        if (ret == -1) printf("can't set bits!");

        ret = ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &baud);
        if (ret == -1) printf("can't set speed!");

        printf("spi mode set as %u\n", mode);

        printf("bits per byte set as %u\n", bits);
        printf("max speed set at %u\n", baud);

        do {
                // Write Enable
                buffer[0] = 0x06;
                transfer(fd, buffer, 1);

                // Read Status
                buffer[0] = 0x05;
                buffer[1] = 0x00;
                transfer(fd, buffer, 2);
        } while (!(buffer[1] & 0x02));

        printf("Status Reg: %x\n", buffer[1]);

        WAIT_FOR_EEPROM(fd)

//      usleep(100);

        // Write Byte

        buffer[0] = 0x02;
        buffer[1] = 0x00;
        buffer[2] = 0x10;
        buffer[3] = 0xAA;
        transfer(fd, buffer, 4);

/*      uint8_t busy = -1;
        do {
                usleep(50);
                buffer[0] = 0x05;
                buffer[1] = 0x00;
                transfer(fd, buffer, 2);
            busy = buffer[1] & 0x01;
    } while (busy);
*/
        WAIT_FOR_EEPROM(fd)

        // Read Byte
        buffer[0] = 0x03;
        buffer[1] = 0x00;
        buffer[2] = 0x10;
        buffer[3] = 0x00;
        transfer(fd, buffer, 4);
        printf("Received byte: %i\n", buffer[3]);

        if (close(fd) > 0) printf("can't close device");

        return 0;
}

int transfer(int spi_file, uint8_t *buffer, int length) {
        //struct spi_ioc_transfer spi[length] = {0};
        int ret = -1;
        struct spi_ioc_transfer tr[length] = {0};

        for (int x=0; x<length; ++x) {
                tr[x].tx_buf            = (unsigned long)(buffer+x);
                tr[x].rx_buf            = (unsigned long)(buffer+x);
                tr[x].len               = sizeof(*(buffer+x));
                tr[x].delay_usecs       = 0;
                tr[x].speed_hz          = baud;
                tr[x].bits_per_word     = bits;
                tr[x].cs_change         = 0;
        };

        ret = ioctl(spi_file, SPI_IOC_MESSAGE(length), &tr);

        if (ret < 1) printf("Transfer Error!!! First Byte Was: 0x%x\n",         buffer[0]);

        return ret;
}

我目前收到两次Transfer Error!!! First Byte Was: 0x5 错误，表明WAIT_FOR_EEPROM(fd) 命令未正确执行。

一开始，WEL 位使用命令 0x06 设置，状态正确报告为 2。从 EEPROM 读取的数据读取为 0 或 211，具体取决于我如何调整代码。它应该是 0xAA (170)。

如果有任何建议，我将不胜感激。

Answer 1

我猜 transfer() 函数负责为每次调用设置和执行一个 SPI 命令。 为什么要使用 'struct spi_ioc_transfer' 数组？ 为什么要遍历缓冲区中的字节数并为每个字节设置一个“spi_ioc_transfer”结构？

看看https://raw.githubusercontent.com/raspberrypi/linux/rpi-3.10.y/Documentation/spi/spidev_test.c