Millisecond precise imaging

Discussion in 'STT Series (obsolete)' started by golgot78, Sep 19, 2016.

  1. golgot78

    golgot78 Cyanogen Customer

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    Hello,

    For professional use it is crucial need to get a very accurate time of the exposure (5 ms resolution or better).
    I am using STT-3200ME and MaximDL 6.08. Camera is connected via USB to my laptop.

    My first approach was of course to use "Measure Shutter Latency" tool of MaximDL but I had a lot of problems with it: discontinuity in 100th of second cells lighting while exposure, probably meaning that the display sequence of my screen was not fast enough to capture this information.
    That made the interpretation of the shutter latency results quite difficult but at least I observed that this shutter latency is fluctuating a lot. And doing an average of it is not acceptable for my application.

    Then we replaced "Measure Shutter Latency" tool by an array of LEDs commanded by a Rapberry running a real-time OS. On the other side, the camera was commanded by a script.
    Both PC controlling the camera by a script and Raspberry controlling the array of LEDs were fed by a common very accurate NTP time.
    The first results we are getting seem to confirm the important fluctuation of shutter latency. Too much to pretend to a 5 ms accuracy.

    I don't know where this fluctuation is coming from.

    Even though I guess I am not the only guy for which time-stamping of the pictures is crucial, I dug it quite deep but yet failed to find a way to get accurately this time information.

    Then I am now thinking to control the shutter more "directly" by script or C, and then time-stamp myself directly the resulting FITS header with the correct value. But is there a way to do that?
    Could you please help me?
    Is there anything left to attempt? for example on the camera control side using SBIG Universal Driver/Library, for example to activate very accurately the shutter in very accurate reproducible timing?

    At the very end, I could imagine to buy an external shutter commanded by TTL signal... but I am not sure there is enough room for that before the focal plane.

    Thanks for reading... and helping!
     
  2. Doug

    Doug Staff Member

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    There will be some variability to the shutter latency. There are processes in the Windows PC and in the camera firmware that have a certain cycle time.

    There are spare I/O bits on the I2C port, which could be configured to provide a trigger input. This would require firmware modification though.

    My I ask what the application is?
     
  3. golgot78

    golgot78 Cyanogen Customer

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    Hello Doug,

    Thanks for answering. The application is for satellite observation and time stamping is crucial for that.
    Your answering sounds promising.
    Could you please explain which port of I2C BUS is concerned (pin 6?) and how to use it in order to control the shutter.
    Is it based on TTL +5V logic programming to trigger the preloaded (via USB port) exposer parameters?
    And how could we get the firmware modification you mentionned?

    Thanks in advance!

    Best Regards,

    Gautier
     
  4. Doug

    Doug Staff Member

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    Yes it would be a TTL pulse on Pin 6. I can ask our firmware developer to put it into his queue, might take 4-8 weeks depending on what else he is working on.

    Also what software are you using to control the camera? It would need to have the option to enable the trigger input. The current release of MaxIm DL has this feature; probably other software does not because the feature was added to the STF cameras relatively recently.
     
  5. golgot78

    golgot78 Cyanogen Customer

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    Hi Doug,

    In fact we are commanding the camera with a Python script through MaximDL. Below is an example on the way we control it:

    def exposeLight(self,length,filterSlot):
    self.__CAMERA = win32com.client.Dispatch(‘Maxim.CCDCamera’)
    self.__CAMERA.Expose(length,1,filterSlot)
    while not self.__CAMERA.ImageReady:
    time.sleep(1)
    self.__CAMERA.SaveImage(‘xxx.fit’)


    We are using MaximDL 6.08. and the camera is connected via USB to the laptop.
    Our initial understanding was that we could keep the camera connection through USB for all the controls and data exchanges which are not “time accuracy” demanding and control the shutter trigger separately via I2C probably via a separate computer (like a Raspberry, synchronized by NTP). But this would be very complex so if you have a simpler solution we are open!

    I don’t really understand the way we could use the trigger directly with MaximDL. Does it mean that we have to abandon the USB interface and then use I2C port or the HTTP REST API not only to trigger the exposure but also to download the images?

    Thanks,

    Best Regards,

    Gautier
     
  6. Doug

    Doug Staff Member

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    MaxIm DL starts the exposure, specifying trigger mode.

    The camera waits, flushing the array, until the trigger arrives. Then the exposure continues normally.
     
  7. golgot78

    golgot78 Cyanogen Customer

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    Hello Doug,
    I do confirm we need such a firmware update and a page of explanation on how to connect I2C and command the trigger.
    Our projet is definitely stuck by the availability of this feature!
    So we pray every day for firmware developper for doing his best to prepare this update as soon as he could.

    By the way, how could we know when the firmware is available?

    Many thanks for your reactivity and time Doug!


    Best Regards,

    Gautier
     
  8. Doug

    Doug Staff Member

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  9. golgot78

    golgot78 Cyanogen Customer

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    Hello Doug,

    I am sorry but I can't reach the link you gave me:
    Diffraction Limited - SBIG / Cyanogen Forum - Error
    You do not have permission to view this page or perform this action.

    I don't really understand why MaximDL also has to be updated. Is it because the firmware update of the camera will be made through MaximDL?

    Best Regards,

    Gautier
     
  10. Doug

    Doug Staff Member

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  11. Doug

    Doug Staff Member

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    External trigger mode is now available for the STT. This is a firmware update, which you can download using the SBIGDriverChecker64
     
  12. golgot78

    golgot78 Cyanogen Customer

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    Hello Doug,

    Thanks for the notification.
    We first updated MaximDL to 6.13 as you suggested and it worked just fine!
    Then we started SBIGDriverChecker64 which tells us we are already up-to-date... (cf. attached screenshot for versions).
    Could you please tell us what is the version we should expect from your patch and confirm it is available from SBIGDriverChecker64 tool.
    Remark: we only tried to update the firmware and did not update the drivers.

    Beyond this update question, could you please explain the way we could eventually control the camera shutter through I2C port. Is there a note or manual for that?

    Thanks in advance!

    Gautier
     

    Attached Files:

  13. Doug

    Doug Staff Member

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  14. golgot78

    golgot78 Cyanogen Customer

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    Hello Doug,

    1. OK for the I2C description in UM but it doesn't tell us which signal has to be transmitted to trigger In pin. Is it a +5V --> 0V during 30 ms or whatever. Also is there another pin to use?

    2. Sorry but you didn't answer the crucial question:
    "Then we started SBIGDriverChecker64 which tells us we are already up-to-date... (cf. attached screenshot for versions).
    Could you please tell us what is the version we should expect from your patch and confirm it is available from SBIGDriverChecker64 tool."

    Best Regards,

    Gautier
     
  15. golgot78

    golgot78 Cyanogen Customer

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    Hello Doug,

    I hope you're doing well.
    I come back to you because we are still waiting for your answers to the questions I asked in the previous messages.

    It is crucial for us to get this patch and to know what trigger signal we have to generate to the proper I2C pins.
    Is there anything I mis-formulated in my question? Do you prefer me to give you a call.

    We are really depending on your answers.

    Thanks in advance,

    Gautier
     
  16. Adam Robichaud

    Adam Robichaud Staff Member

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    Hi Gautier,

    The answers to your questions are as follows:

    1. Keep the pin at Ground (0V). A transition to TTL high (+3.3V) will trigger the exposure on the rising edge. We also have Trigger Out, which lets you know when an exposure is currently in progress (it's synced with Shutter open/close for the duration of the exposure), but using it is optional. See your user's manual for the pin number.

    2. You need to click "Download" to make sure you have the latest drivers available from our site before knowing whether or not your drivers are current. The versions of various software you'll need are: SBIGUDrv.dll v2.94 build 1 or greater, STT GA v2.63, and MaxIm DL v6.13.

    Edit: If you need any assistance installing the patches, please let me know. I'd be happy to assist you.
     
  17. golgot78

    golgot78 Cyanogen Customer

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    Hello Adam,

    Thanks for the explanation, it worked just fine.
    We'll make an attempt tomorrow for the triggerring. Do we just need to connect one wire to pin 6 in order to give the +3.3V signal or is there any other thing to do (i.e. another wire to connect to ground or whatever?)
    I remember there was a dedicated SBIG pdf document on the Wab explaining the process but recently the link to this notice is no more valid. Do you still have this note or equivalent?

    Thanks in advance,

    Best Regards,

    Gautier
     
  18. Doug

    Doug Staff Member

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    You need ground.
     
  19. Doug

    Doug Staff Member

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    Here's the document you referred to. It was written for the old ST-7 series cameras, so I can't vouch for its accuracy for newer models.
     

    Attached Files:

  20. golgot78

    golgot78 Cyanogen Customer

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    Hello Doug and Adam,

    Coooool, it works!
    Many thanks for your help and patience!

    Bye,

    Gautier
     

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