QHY 174 GPS Calibration LED issue // USB Traffic weirdness

wunni
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QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by wunni » Thu Jan 16, 2020 2:21 pm

Hello!

To get a clean SC installation, I uninstalled older SC versions from former testings, deleted all SC directories and cleaned the registry. Than I installed the latest SC version 3.2.6194.
Basicly it works.

GPS issue
After starting SC, the GPS Calibration LED inside the camera is always on (you'll see it with full Gain). But the switch GPS Calibration LED at GPS Controls is Off. I can switch it "ON", then back to "Off", the LED wents off. But as soon as I touch the GPS Calibration LED-switch, the GPS-output freezes.
The status (window GPS Status) remains "Locked", but otherwise it behaves as if GPS is not available. The timestamp in the picture is frozen, also the display in the status bar. But in the picture itself you can see the points running at the top - GPS signals are written into the picture.
If I move one of the calibration sliders now, GPS starts up again. The calibration LED also lights up (depending on the slider setting), no matter what the switch is set to.

USB traffic weirdness
Normally, I set the USB-traffic to zero --> to get the greatest data rate.
If I change the Capture Area to a large field (lets say 800 x 600 to 1920 x 1200), the live image freezes, and also the GPS Status window.
Now I have to move the USB Traffic slider. I have to set the value exactly to 14 or 15 to get the highest frame rate.
If I set the USB Traffic to higher values, I would expect a slower frame rate, but still the Exposure Time set at the Camera Controls.
But If I increase the USB-traffic value, the Exposure time (in the GPS status window) increases as well.

Example: Exposure time set in Camera Controls: 50ms, Mono16, 1920x1200, no binning. Exposure time value from GPS Status window.
USB-traffic: 0
frame rate: 0
Exposure time: (frozen)
-
USB-traffic: 15
frame rate: 20
Exposure time: 50224µs
-
USB-traffic: 50
frame rate: 12.5
Exposure time: 79600µs
-
USB-traffic: 100
frame rate: 6.7
Exposure time: 146200µs
-
USB-traffic: 200 (max)
frame rate: 3.3
Exposure time: 279400µs (You actually see that the exposure time is much longer, that's no pure diplay issue)

Do I need an updated system driver or where do this problems come from?

By the way:
I know Christmas is over, but maybe I can make a wish: The many decimal places on the timestamp in the image down to 100ns are more confusing than helpful. Couldn't it stay with three digits (1ms)? Resp. how can I adjust it?

Best regards,
Niko

hpavlov
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by hpavlov » Thu Jan 16, 2020 7:12 pm

Hello,

This may be a separate issue but because it is related to USB Traffic, I thought I will also report another observed problem related to timestamp accuracy depending on USB Traffic.

The test was done with the EXposure Timer Analyser (EXTA - http://www.dangl.at/menu_hhe.htm) device and showed timestamp errors with USB traffic of 0 and 5 with exposures of 50ms and shorter. The test was done with SharpCap 3.2.5986.

The errors were as follows:

Mono 8, Binning 1x1, Capture Area: 1920x1200;

USB Traffic: 0; Exposure: 0.020; Timestamp Error: 0.032
USB Traffic: 0; Exposure: 0.010; Timestamp Error: 0.021
USB Traffic: 0; Exposure: 0.020; Timestamp Error: 0.014
USB Traffic: 5; Exposure: 0.030; Timestamp Error: 0.039
USB Traffic: 5; Exposure: 0.040; Timestamp Error: 0.047
USB Traffic: 5; Exposure: 0.050; Timestamp Error: 0.068

No dropped frames were observed in these tests and the real optical exposure measured with EXTA agreed with the set exposure in SharpCap. The only problem was the timestamp error for exposures shorter than 50ms. Exposures longer than 50ms with USB Traffic of 5 showed agreement between timestamps and exposure duration with no dropped frames.


Regards,
Hristo

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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by admin » Thu Jan 16, 2020 9:12 pm

Hi,


First I would suggest making sure that you have the option to auto restore camera switched off in the SharpCap options as this may be loading settings when the camera is opened and may have an effect on things like the calibration LED that is unintentional.

I certainly don't see the calibration LED turned on when the cameras started or any problems with lock-ups in the GPS signal. I would certainly suggest an update to the very latest version of SharpCap as the version 3.2.5986 that was mentioned is very old and there have been many updates to the Qhy SDK since then.

One of the things to remember about the USB traffic control (and similar controls on other camera brands) is that we don't expect camera to always work reliably at all values for this control – the control is there so that you can find a value at which the camera does work reliably. That being said, I do see the way that the exposure time reported by the GPS is affected by the position of that control, although as far as I can see the actual exposure length is not varying – certainly the brightness of the image doesn't seem to change. Could it be that the exposure time would be correct if the LED start and end points were adjusted correctly? I've previously played with them and noted that they need different values depending on the USB traffic setting and the exposure length.

I'm not going to claim to be an expert at how the calibration LED timing system works – I've basically set up the controls to allow SharpCap users to take advantage of the configuration in the underlying qhy SDK. I'm not surprised that adjusting either of the two start or end sliders turns the LED on (dependent on position) even if the master switch is off. Perhaps I should make the sliders unavailable when the master switch is off to prevent that from happening?

Cheers, Robin

TimHaymes
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by TimHaymes » Fri Jan 17, 2020 12:33 am

I have set USB traffic set to Zero and im not investigation its effect. Using an LED pulse from a DCF77 receiver (not decoder) I get a 20ms delay in UT when running at 400 fps. Are there any instructions on using the internal LED pulse calibration? I dont see the test LED at all, even on high gain. Is there an optimum exposure ? Any instructions welcome -Thanks, Tim (UK)

procyon12
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by procyon12 » Fri Jan 17, 2020 5:42 am

Hi,

from my experience (SC pro 3.2.6194.0; w7-64bit home premium, Intel i7 2.2GHz, 16GB RAM, SSD) the LED goes on if I move the slider "Calibration End Pos (Fine)" from def. 1000, all the others 3 sliders are default = 0. To see the LED you must push up the gain, with full frame, the LED illuminates only the right side of the sensor. And yes, sometimes the LED is always on... As Robin wrote, you can solve this by (re)using SC default settings (auto restore camera switched off).

The calibration procedure does not appear conclusive..., I Didn't get it working. Are calibration settings (obviously heavily dependent on many parameters) found written to the camera / SC-ini?

Best regards

Christian
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TimHaymes
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by TimHaymes » Fri Jan 17, 2020 12:24 pm

Thanks, I see the LED light now. :D I followed some instructions supplied on the CD that came with the camera "174m_gps_manual.pdf"
dated 25.02.2019. Not a clear translation, and concluded i would set the values back to their default. It looks to me the values are saved in each setting file, so each one would need to be re-saved (so not in an "ini" file). If a definitive set of instructions appear for Dummies, i will re-visit these adjustments :lol: Clear skies... Tim

wunni
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by wunni » Fri Jan 17, 2020 1:50 pm

Hello Robin and Tim,

Robin, thank you for your explanations!

The increasing exponation time is not an virtual effect. You see the image brightening. Also the GPS log shows longer exponations. I did not change the time setting in the Camera Controls, it remained on 50ms.

My problems occured with the most recent SC version, by the way.

Tim - what DCF 77 receiver do you use? 'Normal' DCF receivers cannot deliver a precise signal: The necessarily very narrow bandwidth of the receiver causes a sometimes considerable delay of the output pulse. (We have 77.5kHz...) This is also dependent on the field intensity of the DCF signal. (Just turn the antenna by 45° and repeat the measurement.)
I held a short talk at the ESOP in Berlin 1996 about 'Accuracy limits of DCF-77 receiver modules'. In Berlin I measured a delay of 50..60ms of the receiver's ouput to the direct 77.5kHz-Signal (at this time the most accurate time source available).

For time measurements in the range of milliseconds one should only use 1PPS / GPS as a reference.

Cheers,
Niko

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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by admin » Fri Jan 17, 2020 7:09 pm

Hi,

I did some more testing last night with the GPS camera and found that it looks like the way that the calibration needs to be done has changed somewhat since the last time I updated the SharpCap code. Once upon a time start and end delay values of a few thousand were sufficient for proper calibration, but now values in the millions seem to be the correct result.

What I noticed was that for longer exposures the GPS exposure value is correct. As you reduce the exposure time it becomes incorrect – the point at which it becomes incorrect depends on the value of the USB traffic control. At any particular value of exposure and USB traffic, if you take the time to perform the calibration of the start/end LED positions then the exposure seems to readout correctly - i.e. it matches the expected value from the exposure slider. I tested this for various exposures between 0.5 ms and 50 ms and could get what looked like a correct reading at all points once the calibration was done.

I will try to post the link to an updated version with improved calibration controls and the option to enable a PPS stabiliser kindly donated by the author of OccuRec.

Thanks, Robin

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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by admin » Fri Jan 17, 2020 9:03 pm

Hi,

try this version :

https://d.sharpcap.co.uk/download.html? ... 3.2.6212.0

I have updated the scaling of the coarse/fine sliders for the start/end, locked them out when the LED is off and added the stabilization code from Hristo.

As you can see below, with correct calibration you get the right exposure time result in the GPS data.

I should note that I also found the problem with the GPS showing as locked but not updating occurred if the calibration was significantly incorrect.

Robin
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procyon12
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Re: QHY 174 GPS Calibration LED issue // USB Traffic weirdness

Post by procyon12 » Mon Jan 20, 2020 9:58 pm

Hi,
thanks to Robin and Hristo.
As far as I could test: it works. I've made some tests to check the LED calibration (for my hardware see above). The best how-to is in SC help. I post two self explaining screenshots, maybe you will try to reproduce them.

Regards
Christian
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