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Old 03-18-2016, 10:23 AM   #61
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Quote:
Originally Posted by Ace Dude View Post
There's always some clock drift. That's why we have NTP in the first place. I'd think 1ms should be able to be easily achievable, however, it would be cool just to validate that from a systems integration testing perspective.
Agree, have to look this up and see what can be done. Doesn't necessarily have to be done for the first version of the system though. I'm taking a somewhat pragmatic view to the project and actually "getting it done" is important. There will be room for improvements later as long as I have a good base to stand on. And I believe I have.

Quote:
Originally Posted by AlastairC View Post
This is a blog post on the subject and how to test (as this is a couple of years old you may want to run the test with your new V3): http://blog.remibergsma.com/2013/05/...-pi-keep-time/
Thanks, will do some reading.
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Old 03-18-2016, 10:31 AM   #62
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I wouldn't spend any more time on it now. Get it working functionally and measuring helis through the course and than you can always refine later.

I think you've overcome the hardest part which is determining when the heli enters the start/exit of the course. The overlays you added to the video are excellent. Good job!
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Old 03-19-2016, 04:10 AM   #63
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Friday evening was a long coding evening for me. Added some well deserved mutexes (Locking of data when access by more than one thread) to my multi-threaded code, I had been sloppy..

Then I was onto jitter again. And it's getting even better. I now have a jitter of 3ms or less 99.8% of the frames. I have come this low by inserting a well timed "sleep" in the high priority camera thread. This is a hack, but it seems to starve the thread on CPU time. so when it's ready to do it's business, It has to do it all very fast. I believe there is waiting going on in the camera libraries (there has to be, waiting for frames coming in from the hardware), I want those waits to never trigger.

Tested over the night for eight hours straight, pushing out 3.500.000 jpegs over two cameras! So the program is also stable.

Today I'm going to look at battery power for the camera stations. I have LM7805 regulators in my inventory. These are good for about 1A (About half of what a PI states it needs). Perhaps they will still work, since I'm not using any USB devices, not even a keyboard. I will run these on 2S Lipo. You can run these on main power, but I'm not keen on having to drag 100M+ more cable to the field.

I have also ordered 2x60M Cat6 ethernet. So progress has been made.
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Old 03-19-2016, 04:35 AM   #64
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Interesting. Never thought of jitter due to software. Looking forward to building out one these once you think it's complete. Cheers.
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Old 03-19-2016, 05:42 AM   #65
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7805 in action, it does work. But the Pi definitely uses some power. 7805 being linear throws away quite a bit too.. Perhaps I should just order a couple of BECs...

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Old 03-19-2016, 06:43 AM   #66
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Get that fancy BEC from R2...........
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Old 03-19-2016, 07:18 AM   #67
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$3, hobbyking As long as they are switching.
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Old 03-19-2016, 11:36 AM   #68
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I came to my senses and took a CC Bec Pro. a 6s5000 can power the PI for an afternoon easy. So don't throw away those old and busted packs.
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Old 03-19-2016, 12:04 PM   #69
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Look at that! Starting to look like Camera stations.

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Old 03-19-2016, 12:22 PM   #70
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Cool!
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Old 03-19-2016, 01:55 PM   #71
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Maybe missed it in previous posts, but what kind of camera are you using with the Pi3?
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Old 03-19-2016, 02:04 PM   #72
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It's the standard camera for the PI. It has a socket on the board to connect to. Cost like 30$ or so.
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Old 03-19-2016, 05:56 PM   #73
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I disconnected the 6s5000 now. After 8 hours straight runtime the cells read 3.94. So you can run a PI (actually doing something) a full day on one of those. Not bad.

I've been working on the base station GUI a bit, it's getting there. But I got tired and felt I messed up more than I got done, time to sleep...
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Old 03-21-2016, 07:42 AM   #74
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Today, or actually yesterday was the day this system measured the speed of something for the first time!

The cameras and distance is not calibrated, I guessed a bit.. But looks good.

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Old 03-21-2016, 03:57 PM   #75
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Today was measuring day. We pulled this off like champs. The upper line which isn't on the picture was pretty much exactly 100M after the four corners where placed. We used a laser meter and measuring tape.

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Old 03-21-2016, 04:31 PM   #76
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Nice... Looking promising Linus...

M
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Old 03-22-2016, 02:44 AM   #77
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The system is pretty much good enough for first real testing now. There are rough edges when it comes to things like usability but it should give respectable results. I have all needed hardware (one station is still running Pi 2 though). Network cables are at the post office. A friend have another BEC pro for the other camera pod.

Hopefully the weather at easter weekend is good so I can set it up and do some real testing. Exciting is the word.
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Old 03-22-2016, 02:53 AM   #78
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To calculate some on the pricing of this so far, this is Swedish prices.

2xPi 3 = $120
2xPi Camera = $60
2xPi Case = $20
2x60M network cable = $70
2xCamera stands = $25
2xBec Pro = $70
Old 100Mbit switch = parts box.

For a total of about $365, not bad. There is also a need for a somewhat up to date laptop (Or a big ass gaming station if you lug that to the field), preferably SSD and ethernet.

The BEC Pros aren't necessarily needed but I have so many half assed 6S 5000 it's cheaper to go with a 6S setup rather than buy new 2S batteries. And since we are using hobby grade equipment which will run all day long without interruption it's better to oversize and use a good BEC. I checked hobbyking, but didn't find anything I wanted. I don't do clone hardware.
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Old 03-23-2016, 01:12 AM   #79
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Now that is a price point that I can live with. Great work once again Linus
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Old 03-23-2016, 08:54 AM   #80
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Thanks!

I have done som testing using a digital watch (smartphone) which both cameras where filmed at the same time. They cameras are very exact, and they should be but before you really do testing you don't really know.

I filmed the phone and later reviewed the material in the "base-station-program", Since the images are to smudgy as this close distance I checked when the seconds turned over. And they do it exactly on the same frame on both cameras, they can even catch the ghosting (pixels turning off) with authority on the same timestamp.

Since they are 90fps cameras and they are not synced on the shutter the theoretical they can actually capture the screen at the same time is about 5.5ms worst case (1 frame being 11ms, and they can be completely out of sync, running there own clocks and all that). They do howerver also timestamp there own images and that is more important.

After reviewing and taking things into account (Smartphone screen only 60fps for example), I really do believe the two cameras have a combined accuracy of about 5 milliseconds. Doing some math on this would give a camera accuracy of within 1kmh if you run 250kmh on 100M... I'm so hoping I'm interpreting this correctly, because the results looks awesome.

Now you may not hit the camera line perfectly, which would add half a frame error or so but still extremely good. And interpolation beetween frames is possible in some future version.

I'm actually not really believing what I'm seeing here...
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