CODEWITHSUNDEEP
cameraembeddedusbwebcam
Mir Milad Hosseiny
Mir Milad Hosseiny

Reputation: 2857

USB Camera Protocol

I want to connect a USB camera to an embedded device. My device OS is embedded Linux and supports USB Host. I can read and write to USB port easily, but I don't know how I can capture an image from camera. Is there any standard protocol for USB camera that I can capture image?

Upvotes: 2

Views: 3400

Answers (1)

Flexo - Save the data dump
Flexo - Save the data dump

Reputation: 88711

Most cameras that support this use Picture Transfer Protocol (PTP). In Linux there is support for this via libgphoto2 for a lot of cameras.

You can list connected devices using something like:

    CameraList      *xlist = NULL;

    ret = gp_list_new (&xlist);
    if (ret < GP_OK) goto out;
    if (!portinfolist) {
        /* Load all the port drivers we have... */
        ret = gp_port_info_list_new (&portinfolist);
        if (ret < GP_OK) goto out;
        ret = gp_port_info_list_load (portinfolist);
        if (ret < 0) goto out;
        ret = gp_port_info_list_count (portinfolist);
        if (ret < 0) goto out;
    }
    /* Load all the camera drivers we have... */
    ret = gp_abilities_list_new (&abilities);
    if (ret < GP_OK) goto out;
    ret = gp_abilities_list_load (abilities, context);
    if (ret < GP_OK) goto out;

    /* ... and autodetect the currently attached cameras. */
    ret = gp_abilities_list_detect (abilities, portinfolist, xlist, context);
    if (ret < GP_OK) goto out;

    /* Filter out the "usb:" entry */
        ret = gp_list_count (xlist);
    if (ret < GP_OK) goto out;
    for (i=0;i<ret;i++) {
        const char *name, *value;

        gp_list_get_name (xlist, i, &name);
        gp_list_get_value (xlist, i, &value);
        if (!strcmp ("usb:",value)) continue;
        gp_list_append (list, name, value);
    }
out:
    gp_list_free (xlist);
    return gp_list_count(list);

(Taken from libgphoto2-2.4.11/examples/autodetect.c)

Upvotes: 2

Related Questions