Setting fixed focus on the CAM500B from the NanoPI NEO AIR

[dmorse]

I'm completely new to all of this, so I apologies if I have missed something obvious.

I'm working on a project where I capture image data from a CAM500B attached to a NanoPi NEO Air. I need to be able to capture the images as quickly as possible so since I know how far away the objects I'm capturing are going to be I would like to set the focus to a fixed length relatively close to the camera. I have been able to disable the autofocus with the following code.

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    struct v4l2_queryctrl focus_vals;
    memset(&focus_vals, 0, sizeof(focus_vals));
    focus_vals.id = V4L2_CID_FOCUS_AUTO;
    if(0 == xioctl(vd->fd, VIDIOC_QUERYCTRL, &focus_vals)){
        DBG("V4L2 Got V4L2_CID_FOCUS_AUTO  vals %s\n", (focus_vals.flags & V4L2_CTRL_FLAG_DISABLED) ? "DISABLED" : "ENABLED");
    }
    else{
        DBG("V4L2 No V4L2_CID_FOCUS_AUTO valsi errno %d\n", errno);
    }

    struct v4l2_control focus_control;
    memset(&focus_control, 0, sizeof(focus_control));
    focus_control.id = V4L2_CID_FOCUS_AUTO;
    focus_control.value = 1;
    if(0 == xioctl(vd->fd, VIDIOC_S_CTRL, &focus_control)){
        DBG("V4L2 Autofocus disabled\n");
    }
    else{
        DBG("V4L2 Autofocus not set\n");
    }   

So far so good. This works and the camera stays in a hyperfocal position. (note that xioctl() is just a wrapper around ioctl() that retries). The problems come in when I try to set the focus to a particular value with the following code

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    memset(&focus_vals, 0, sizeof(focus_vals));
    focus_vals.id = V4L2_CID_FOCUS_ABSOLUTE;
    if(0 == xioctl(vd->fd, VIDIOC_QUERYCTRL, &focus_vals)){
        DBG("V4L2 Got V4L2_CID_FOCUS_ABSOLUTE min %d, max %d\n", focus_vals.minimum, focus_vals.maximum);
    }
    else{
        DBG("V4L2 No V4L2_CID_FOCUS_ABSOLUTE vals errno %d\n", errno);
    }

    memset(&focus_control, 0, sizeof(focus_control));
    focus_control.id = V4L2_CID_FOCUS_ABSOLUTE;
    focus_control.value = 50;
    int ret =0;
    if(0 == (ret =xioctl(vd->fd, VIDIOC_S_CTRL, &focus_control))){
        DBG("V4L2 focus level set!!!!!!!!!!\n");
    }
    else{
        DBG("V4L2 focus level not set. Ret: %d errno: %d\n", ret, errno);
    }

The output from these two pieces of code, run in order, is as follows

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 DBG(v4l2uvc.c, enumerateControls(), 834): V4L2 Got V4L2_CID_FOCUS_AUTO  vals ENABLED
 DBG(v4l2uvc.c, enumerateControls(), 845): V4L2 Autofocus disabled
 DBG(v4l2uvc.c, enumerateControls(), 854): V4L2 Got V4L2_CID_FOCUS_ABSOLUTE min 0, max 127
 DBG(v4l2uvc.c, enumerateControls(), 880): V4L2 focus level not set. Ret: -1 errno: 22

The interesting thing here is that the call to ioctl with VIDIOC_QUERYCTRL for V4L2_CID_FOCUS_ABSOLUTE seems to indicate that this functionality is available, but when I try to set the focus I get errno set to 22, EINVAL.

I've dumped the name of the driver that my code says this device is using, and it is called "sunxi-vfe". I don't see this name in the friendlyarm git repo anywhere, but I have found it here https://github.com/allwinner-zh/linux-3.4-sunxi/blob/master/drivers/media/video/sunxi-vfe/vfe.c. Looking through the function vidioc_s_ctrl (which I assume is called when I call ioctl(vd->fd, VIDIOC_S_CTRL, &focus_control) in both instances) it looks like if this function forks for V4L2_CID_FOCUS_AUTO it shoudl also work for V4L2_CID_FOCUS_ABSOLUTE.

My distro and kernel are as follows.

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root@FriendlyARM:~# cat /etc/issue
Ubuntu 16.04.1 LTS \n \l

root@FriendlyARM:~# uname -a 
Linux FriendlyARM 3.4.39-h3 #3 SMP PREEMPT Tue Feb 14 15:07:44 CST 2017 armv7l armv7l armv7l GNU/Linux
root@FriendlyARM:~#

[Xeye]

Hi,
I am working on similar task as you do. Where did you get the ov5640 driver file?
I found other sensors .ko files, but not any for ov5640.