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在Mac OS X上无法使用C + libusb声明USB接口

Unable to claim USB interface with C + libusb on Mac OS X

我有一个使用PIC32单片机构建的复合USB + CDC设备，我正在尝试连接到该设备并从Mac将一些数据发送到CDC数据接口端点。

我知道电路可以工作100％，因为该设备同时注册为HID操纵杆，并且我可以使用/dev/tty.usbmodemfa132上的Zoc终端连接到该设备。我可以使用Zoc发送命令，并通过闪烁电路上的一些LED来查看我的MCU对这些命令的响应。

我在Mac OS X Mavericks上运行此程序，但是在几个星期前我在Mountain Lion上放弃的类似示例也遇到了同样的问题。

我的代码如下所示：

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// Includes -----------------------------------------------------------------------------------------------------------
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <libusb-1.0/libusb.h>
#include <unistd.h>

// Defines ------------------------------------------------------------------------------------------------------------
#define VID 0x04d8
#define PID 0x005e
#define CDC_DATA_INTERFACE_ID 2

// Function Declarations ----------------------------------------------------------------------------------------------
void print_device(libusb_device *device);
void send(libusb_context *usb_context, uint16_t vid, uint16_t pid);

// Function Definitions -----------------------------------------------------------------------------------------------

/**
* main
*/
int main(int argc, char **argv)
{
libusb_device **usb_devices = NULL;
libusb_context *usb_context = NULL;
ssize_t device_count = 0;
bool debug_enabled = false;
int c;

// Collect command line attributes
while ( (c = getopt(argc, argv,"d")) != -1) {
switch (c) {
case 'd':
debug_enabled = true;
break;
}
}

// Initialize USB context
int result = libusb_init(&usb_context);
if(result < 0) {
printf("Unable to initialise libusb!");
return EXIT_FAILURE;
}

// Turn debug mode on/off
if(debug_enabled) {
libusb_set_debug(usb_context, 3);
}

// Get USB device list
device_count = libusb_get_device_list(usb_context, &usb_devices);
if(device_count < 0) {
puts("Unable to retrieve USB device list!");
}

// Iterate and print devices
puts("VID PID Manufacturer Name\
------ ------ -------------------");
for (int i = 0; i < device_count; i++) {
print_device(usb_devices[i]);
}

// Attempt to send data
send(usb_context, VID, PID);

// Cleanup and exit
libusb_free_device_list(usb_devices, 1);
libusb_exit(usb_context);
return EXIT_SUCCESS;
}

/**
* print_device
*/
void print_device(libusb_device *device)
{
struct libusb_device_descriptor device_descriptor;
struct libusb_device_handle *device_handle = NULL;

// Get USB device descriptor
int result = libusb_get_device_descriptor(device, &device_descriptor);
if (result < 0) {
printf("Failed to get device descriptor!");
}

// Only print our devices
if(VID == device_descriptor.idVendor && PID == device_descriptor.idProduct) {
// Print VID & PID
printf("0x%04x 0x%04x", device_descriptor.idVendor, device_descriptor.idProduct);
} else {
return;
}

// Attempt to open the device
int open_result = libusb_open(device, &device_handle);
if (open_result < 0) {
libusb_close(device_handle);
return;
}

// Print the device manufacturer string
char manufacturer[256] ="";
if (device_descriptor.iManufacturer) {
libusb_get_string_descriptor_ascii(device_handle, device_descriptor.iManufacturer,
(unsigned char *)manufacturer, sizeof(manufacturer));
printf(" %s", manufacturer);
}

puts("");

libusb_close(device_handle);
}

/**
* send
*/
void send(libusb_context *usb_context, uint16_t vid, uint16_t pid)
{
libusb_device_handle *device_handle;
device_handle = libusb_open_device_with_vid_pid(usb_context, vid, pid);

if (device_handle == NULL) {
puts("Unable to open device by VID & PID!");
return;
}
puts("Device successfully opened");

unsigned char *data = (unsigned char *)"test";

if (libusb_kernel_driver_active(device_handle, CDC_DATA_INTERFACE_ID)) {
puts("Kernel driver active");
if (libusb_detach_kernel_driver(device_handle, CDC_DATA_INTERFACE_ID)) {
puts("Kernel driver detached");
}
} else {
puts("Kernel driver doesn't appear to be active");
}

int result = libusb_claim_interface(device_handle, CDC_DATA_INTERFACE_ID);
if (result < 0) {
puts("Unable to claim interface!");
libusb_close(device_handle);
return;
}
puts("Interface claimed");

int written = 0;
result = libusb_bulk_transfer(device_handle, (3 | LIBUSB_ENDPOINT_OUT), data, 4, &written, 0);
if (result == 0 && written == 4) {
puts("Send success");
} else {
puts("Send failed!");
}

result = libusb_release_interface(device_handle, CDC_DATA_INTERFACE_ID);
if (result != 0) {
puts("Unable to release interface!");
}

libusb_close(device_handle);
}

我收到以下错误输出：

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libusb: 0.828223 error [darwin_open] USBDeviceOpen: another process has device opened for exclusive access
libusb: 0.828241 info [darwin_open] device open for access
Device successfully opened
Kernel driver doesn't appear to be active
libusb: 0.828641 error [darwin_claim_interface] USBInterfaceOpen: another process has device opened for exclusive access
Unable to claim interface!
libusb: 0.828766 info [event_thread_main] thread exiting

有什么方法可以释放其他过程中的USB设备，释放它以便我可以声明它吗？

有没有其他方法可以连接到/dev/tty.usbmodemfa132以向USB设备上的CDC接口发送和接收数据？

也许是libusb的替代品？

相关讨论

那就对了。尽管libusb在Linux中似乎是功能强大的，但是您不能使用它来连接Mac OS X上的USB CDC接口，因为AppleUSBCDCACM驱动程序已经声明了该接口。

您应该做的是使用人们连接到串行端口的标准方法。这将更容易，因为您不必担心端点和批量传输等。这是我为基于CDC的产品之一编写的一些跨平台C代码示例，该产品连接到COM端口以读取和写入一些数据(源)。它使用标准功能open，read和write。

// Uses POSIX functions to send and receive data from a Maestro.
// NOTE: You must change the 'const char * device' line below.

#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>

#ifdef _WIN32
#define O_NOCTTY 0
#else
#include <termios.h>
#endif

// Gets the position of a Maestro channel.
// See the"Serial Servo Commands" section of the user's guide.
int maestroGetPosition(int fd, unsigned char channel)
{
unsigned char command[] = {0x90, channel};
if(write(fd, command, sizeof(command)) == -1)
{
perror("error writing");
return -1;
}

unsigned char response[2];
if(read(fd,response,2) != 2)
{
perror("error reading");
return -1;
}

return response[0] + 256*response[1];
}

// Sets the target of a Maestro channel.
// See the"Serial Servo Commands" section of the user's guide.
// The units of 'target' are quarter-microseconds.
int maestroSetTarget(int fd, unsigned char channel, unsigned short target)
{
unsigned char command[] = {0x84, channel, target & 0x7F, target >> 7 & 0x7F};
if (write(fd, command, sizeof(command)) == -1)
{
perror("error writing");
return -1;
}
return 0;
}

int main()
{
// Open the Maestro's virtual COM port.
const char * device ="\\\\\\\\.\\\\USBSER000"; // Windows,"\\\\\\\\.\\\\COM6" also works
//const char * device ="/dev/ttyACM0"; // Linux
//const char * device ="/dev/cu.usbmodem00034567"; // Mac OS X
int fd = open(device, O_RDWR | O_NOCTTY);
if (fd == -1)
{
perror(device);
return 1;
}

#ifndef _WIN32
struct termios options;
tcgetattr(fd, &options);
options.c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
options.c_oflag &= ~(ONLCR | OCRNL);
tcsetattr(fd, TCSANOW, &options);
#endif

int position = maestroGetPosition(fd, 0);
printf("Current position is %d.\
", position);

int target = (position < 6000) ? 7000 : 5000;
printf("Setting target to %d (%d us).\
", target, target/4);
maestroSetTarget(fd, 0, target);

close(fd);
return 0;
}