2

我在尝试通过 JNI 在 Android (Gingerbread) 中使用 I2C 设备时遇到问题。

问题在于 I2C_SLAVE ioctl 调用。以下代码在编译成独立程序时有效:

    int main(int argc, char *argv[])
{
    int fd = -1;
    long rc;
    int addr = 0x22;


  if ( fd  < 0 ) {
      fd = open(radio_device, O_RDWR);
  }

#define I2C_SLAVE 0x0703

  if ( (rc = ioctl(fd, I2C_SLAVE, addr)) < 0 ) {
      printf("RadioService: I2C slave addr failed! rc=%d errno= %d [%s]\n", rc, errno, strerror(errno));
  }
  else {
      printf("RadioService: I2C slave addr 0x%x set\n", addr);
  }

  return 0;

}

运行时输出(通过adb shell):

~ # testi2c
RadioService: I2C slave addr 0x22 set

但是,相同的代码不能作为 JNI 库的一部分工作:

void Java_biz_lectronix_android_radio_RadioService_nativeInit(JNIEnv* env, jclass clazz)
{
    long rc;
    int addr1 = 0x22;
    int addr2 = 0x18;

    if ( fd = open(radio_device, O_RDWR) < 0 ) {
        __android_log_print(ANDROID_LOG_ERROR, "RadioService", "I2C open failed! %s", strerror(errno));
    }
    else {
        __android_log_write(ANDROID_LOG_WARN, "RadioService", "Opened fd");
    }

    __android_log_print(ANDROID_LOG_ERROR, "RadioService", "I2C_SLAVE [0x%x], addr = %d (0x%x)", I2C_SLAVE, addr1, addr1 );

    if ( (rc = ioctl(fd, I2C_SLAVE, addr1)) < 0 ) {
        __android_log_print(ANDROID_LOG_ERROR, "RadioService", "I2C slave addr1 failed! rc=%d errno= %d [%s]", rc, errno, strerror(errno));
    }
    else {
        __android_log_print(ANDROID_LOG_WARN, "RadioService", "I2C slave addr1 %d set", addr1);
    }

    if ( (rc = ioctl(fd, I2C_SLAVE, addr2)) < 0 ) {
        __android_log_print(ANDROID_LOG_ERROR, "RadioService", "I2C slave addr2 failed! rc=%d errno= %d [%s]", rc, errno, strerror(errno));
    }
    else {
        __android_log_print(ANDROID_LOG_WARN, "RadioService", "I2C slave addr2 %d set", addr2);
    }

    return;
}

日志输出:

01-02 03:03:10.904: E/RadioService(1602): I2C_SLAVE [0x703], addr = 34 (0x22)
01-02 03:03:10.904: E/RadioService(1602): I2C slave addr1 failed! rc=-1 errno= 25 [Not a typewriter]
01-02 03:03:10.904: E/RadioService(1602): I2C slave addr2 failed! rc=-1 errno= 25 [Not a typewriter]

有谁知道这里可能出了什么问题?

4

1 回答 1

1

I2C 接口实际上根本不是问题。问题是这一行:

if ( fd = open(radio_device, O_RDWR) < 0 ) {

应该是这样的(注意括号):

if ( ( fd = open(radio_device, O_RDWR) ) < 0 ) {

因此,打开了 I2C 设备,但比较的优先级高于 C 中的分配。比较失败,将 0 分配给 fd - 即stdin. 然后ioctl()调用失败,因为 I2C_SLAVE 是不适合设备的 ioctl 命令。

于 2013-07-19T03:43:02.747 回答