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20 Aug 2017
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TOPIC: PHD2 on RPi3 running INDI Server?

PHD2 on RPi3 running INDI Server? 2 weeks 3 hours ago #18355

Hi everyone,

I am running INDI server on a RPi3 to which I connect from a MacBook Pro. The connection between Mac and RPi3 occurs through an ad-hoc WiFi connection. I would like to use PHD2 for guiding as I found it gives the best results with my mount, and I was wondering which option be the best, quickest and most accurate between the following:

1) Running PHD2 on my Mac;
2) Running PHD2 on my RPi3;

My main focus is to get quick and reliable guiding, but I wonder whether a direct WiFi connection is fast enough for the data to be sent from the RPi3 to the Mac, processed, and sent back the mount.

Regarding option no. 2, would it suffice to enter the Pi's IP address in the Host field?

Do you guys have suggestions you would like to share?

Cheers,

Maurizio

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PHD2 on RPi3 running INDI Server? 2 weeks 3 hours ago #18357

I assume you run KStars on Mac. If it is the case it's better to run PHD2 on RPi (to minimize data transfers). However you need VNC connection to RPi to start and control PHD2. If it's not an option for you you need to run PHD2 on Mac but wireless link might be an issue. Especially while your captured image from the main CCD is downloaded to Mac over wireless - it saturates the link pretty effectively. You can try it anyway.

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PHD2 on RPi3 running INDI Server? 2 weeks 3 hours ago #18358

Thanks for your quick reply!

I do use KStars on my Mac and I use VNC to connect to the RPi, which anyway has a touchscreen so it's fairly easy to start and control applications. I will give it a try and see how it works!

Would you also suggest stopping VNC while acquiring/guiding?

Thanks!

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PHD2 on RPi3 running INDI Server? 2 weeks 2 hours ago #18359

You're welcome. VNC might eat a lot of bandwith, depending on your screen resolution. I would disconnect it while guiding.
Also you can consider running everything on RPi i.e. KStars and PHD2. This way you use your wireless for VNC only and can disconnect Mac anytime not loosing your imaging session if the link gets down. Try ready to use Astroberry Server image for your RPi. If you don't like it you can come back to your standard setup.

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PHD2 on RPi3 running INDI Server? 1 week 6 days ago #18375

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this really depends on what kind of guide camera you are using, and what it's bandwidth requirements are. If you are fetching 1 frame a second with a small frame, it wont make a huge difference. OTOH, if you are trying to use a 30fps video stream, that's going to suck down a ton of bandwidth, and likely get rather far behind on a slow wifi connection.

It also makes a huge difference what kind of wifi connection it is. An older g mode 2.4ghz radio runs at a maximum on air rate of 54mbit, which will result in 27mbit thruput under ideal conditions. OTOH, if it's a 5ghz AC unit, it can have on air rates well over a gigabit, and result in 800mbit overall system thruput under ideal conditions. Not all wifi is created equally. N mode on 2.4ghz advertises 300mbit, most are only capable of 150, and can only sustain on the order of 70mbit under ideal conditions.

The other issue is your conditions for wifi. on 2.4 ghz your thruput will cut in half for every 75 to 100 feet of separation between them, and it cuts in half for each and every wall between them. At 100 foot distance with two walls in the way, you will be lucky to keep 10mbit sustained. 5ghz is much worse, thruput cuts in half for every 50 feet of separation, and by a factor of 4 when it goes thru the first wall, it rarely manages to make it thru a second wall.

And these numbers dont account for any band congestion. If you are in an area with lots of other wifi access points, or security cameras running on those bands, the numbers can easily fall off by a factor of 10.

This is a subject I deal with every day, the network I manage has over 5000 access points in 1000 edge node locations, so we see it all. This is why even tho we are in a fairly clean wifi environment here at our farm, we still see plenty of contention from neighbors access points and security cameras, so I ran conduits with optical fiber between the house and the dome.

Oh, and one more detail I forgot to mention, what kind of antennas on your wifi gadget make a huge difference. As an example, the rpi3 on board stuff is a horribly poor performer, dont even consider that one for any real distance at all. It works ok for a connection 'in the same room', but, put 100 feet of distance between it and the access point (or other device for ad-hoc) and the signals will be barely measurable. moreso if the other gadget is another one with equally poor antennas.

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Last Edit: by gerryr.

PHD2 on RPi3 running INDI Server? 1 week 5 days ago #18389

Hi Gerryr,

thanks for your exhaustive reply! I did benchmark my direct wifi connection using iperf and it turned out to be approximately 45 Mb/sec over a distance of less 2 meters. I am not planning to take my Mac a long distance away from my scope anyway. Just being able to sit in my car or at picnic table while the scope is taking pictures will be enough. If my Mac had an ethernet port, I would have definitely be using a cable to connect to the RPi. In the beginning, both my Mac and the RPi were connected to my home WiFi router for testing, and I only got a top speed of 9 Mbit/sec. Now it makes sense in the light of your explanation, as the router is downstairs and there are a few walls in between. That's what made me go for a direct WiFi.

Kaczorek, I think I have never really considered running KStars/Ekos locally on a RPi3, as I thought it would be too demanding for that small thing, but apparently it's not! How smoothly does KStar run on a RPi3? I should definitely give Astroberry a try.

Thanks!

Maurizio

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Last Edit: by m.baldassarre.85.

PHD2 on RPi3 running INDI Server? 1 week 5 days ago #18392

You could also consider a usb-c to ethernet adapter. You can get a good quality one for about $20-25

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