sja1000 代码

sja1000 是一款 CAN 控制器，可以通过 SPI 接口与微处理器进行通信。以下是一个简单的 sja1000 的初始化代码片段：

#include <linux/spi/spi.h>

#define SJA1000_CANCTRL_REG     0x0F
#define SJA1000_CANSTAT_REG     0x0E
#define SJA1000_BTR0_REG        0x06
#define SJA1000_BTR1_REG        0x07

struct spi_device *sja1000_spi_dev;

int sja1000_init(void)
{
    struct spi_message msg;
    struct spi_transfer xfers[2];
    unsigned char buf[3];

    // 初始化 SPI 设备
    sja1000_spi_dev = spi_alloc_device(spi_bus, spi_dev);
    if (!sja1000_spi_dev)
        return -ENODEV;
    spi_add_device(sja1000_spi_dev);

    // 复位 sja1000 控制器
    buf[0] = 0xC0;
    xfers[0].tx_buf = buf;
    xfers[0].len = 1;

    // 设置 sja1000 控制器的波特率为 500Kbps
    buf[0] = SJA1000_BTR1_REG;
    buf[1] = 0x01;
    buf[2] = 0x1C;
    xfers[1].tx_buf = buf;
    xfers[1].len = 3;

    spi_message_init(&msg);
    spi_message_add_tail(&xfers[0], &msg);
    spi_message_add_tail(&xfers[1], &msg);
    spi_sync(sja1000_spi_dev, &msg);

    // 检查 sja1000 控制器是否初始化成功
    spi_read(sja1000_spi_dev, SJA1000_CANSTAT_REG, 1, buf);
    if ((buf[0] & 0xC0) != 0x00)
        return -ENODEV;

    return 0;
}