Strobe signal output on Pointgrey Firefly MV using libdc1394

Question

I am using a Pointgrey Firefly MV (FFMV-03M2M/C to be precise) and want to trigger some external device with every shutter start. According to the datasheet, the camera supports IIDC 1.31 and also provides four GPIOs usable as a trigger and/or strobe signal outputs. As described in section 4.11.3 of the IIDC standard it should be possible to configure those strobe signal outputs using IIDC.

My application is implemented in C++ and uses libdc1394 to access and control the camera. So far, everything works quite nicely, but I cannot manage to configure the strobe signal outputs. As far as I understand libdc and IIDC it should be possible to enable the first output as follows (camera is a pointer to a valid dc1394camera_t):

dc1394error_t err;
uint64_t strobe_offset = 0x200;
uint32_t strobe_settings = 0;

err = dc1394_get_strobe_register(camera, strobe_offset, &strobe_settings);
if (err == DC1394_SUCCESS) {
    /* Set bits 6 (strobe on) and 7 (active-high level)
       IIDC uses msb 0, so we need to shift by 25/24 instead of 6/7 */
    strobe_settings = strobe_settings | (1 << 25) | (1 << 24);

    err = dc1394_set_strobe_register(camera, strobe_offset, strobe_settings);

}

if (err != DC1394_SUCCESS) {
    log(LOG_ERROR, "Failed to set strobe.");
}

This does not generate any errors, but it also does not turn on the strobe signal output (even though the camera is capturing frames). I also tried all the other outputs by using a different offset (0x204, 0x208 and 0x20C) but to no avail. Then I checked all the availability inquiry fields at Strobe_CTRL_Inq and Strobe_[0123]_Inq but they all report that the strobe signal outputs are present. But interestingly, the On/Off_Inq field in Strobe_[0123]_Inq tells me that it is not possible to switch the output on or off while the Polarity_Inq tells me that I could change the polarity setting (which I actually can't because you can only change settings when the strobe signal output is switched on). I tried configuring the outputs using the windows based driver utility provided by Pointgrey and there it works without any problems.

Any ideas what I might be doing wrong? Or is this camera not IIDC compatible in this regard?

Update: Ok, I tried three ways to enable the strobe output: Using my orignal code, using the absolute offset 0x1300 as suggested in the answer and using the offset 0x1110/0x1114 as written in the PointGrey register reference manual. I also tried setting delays, durations and/or directions (even though PIOs are not to be confused with the strobe outputs). No combination of registers and flags works so far. Maybe it is a bug in libdc1394 or PointGrey does some other magic in their proprietary driver. For now I give up and will try to find a different solution for triggering an external device.

Guy Sirton · Accepted Answer · 2011-02-13T00:46:58.777

Browsing through the (accessible, can't get to the technical reference) camera documentation it seems like you need to set a direction for the GPIOs, that is whether they are inputs or outputs. The documentation describes a PIO_DIRECTION register at 0x11F8 where low signifcant bits control whether the IO is input (0) or output (1). Perhaps your problem is that the direction is not set?

http://ptgrey.com/support/downloads/documents/TAN2005002_Output_strobe_signal_pulse.pdf

Comparing the camera register map with the standard it seems like the camera should support this. I can't find any documentation for get/set_strobe_register API in libdc1394. Perhaps get or set_register using the camera documented register offsets would work better. How did you figure 0x200 as your offset?

This http://www.cs.unc.edu/Research/stc/FAQs/Cameras_Lenses/PtGrey/DcamRegisterRefManual.pdf documents the register you're trying to access at 0x1300 so perhaps there is some fixed known offset applied for accessing "strobe" registers? Again, perhaps using set_register will allow access to all the camera registers directly so you can use the older set documented.

Another thing is that you need to set a delay and count for the strobe.

Thank you for your answer. The 0x200 offset can be found in the IIDC standard documentation (section 4.11.3) and is relative to the strobe register offset. If I use the absolute offset 0x1300 together with dc1394_get_control_register I get the same results (dc1394_get_register does not work and returns DC1394_FAILURE). I now discovered the offset 0x1110 - 0x1140 in the second document you mentioned and it seems to be promising. Again, thanks for your help! — Simon Lehmann, Feb 15 '11 at 15:09
I tried accepting this answer, but somehow I am not able to do so... is it not possible to accept an answer after the bounty has ended? — Simon Lehmann, Feb 15 '11 at 16:08

Strobe signal output on Pointgrey Firefly MV using libdc1394

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