[hpsdr] Problems building ghpsdr receiver client (from ghpsdr3 project) on Mac OSX

[Jeremy McDermond]

On Jan 9, 2012, at 8:05 AM, Mark Leone wrote:

> Jeremy, I see that you did something similar with Mac-Ghpsdr. Did you run
> into any other issues that I'm likely to encounter with ghpsdr3?

I wish I could tell you, but I honestly don't recall.  I modified the ghpsdr code like three years ago and haven't really looked at it since.

> BTW I did
> try to run Heterodyne. It looks like a nice app; but right now I have a
> problem making the Ethernet interface work for my configuration. The Mac is
> a laptop, connected to a wireless router. Metis is connected to an Ubuntu
> system wired Ethernet port, and a second (wireless) interface on the Ubuntu
> system connects to the aforementioned wireless router.
> 
> I don't know whether the high data rate connection to Metis will work
> satisfactorily through my wifi router, but I want to give it a try. I
> implemented IP forwarding on the Ubuntu system, and the MacBook can ping all
> the way through to Metis. It would be helpful if Heterodyne allowed me to
> specify the Metis Ethernet address, in which case I could connect with my
> current configuration. Since Heterodyne relies only on the discovery
> protocol, I need to implement a bridge between the two Ubuntu Ethernet
> interfaces, so the broadcast frames reach Metis. I did this with Ubuntu
> bridge-tools, but it's not working correctly. I have a post on the Ubuntu
> forums about it (http://ubuntuforums.org/showthread.php?t=1906359), and if I
> get it working, I'll post the results here.

I'm not quite sure what you're describing here, but I'm surprised that ping is working.  The reason you can't specify the Metis ethernet address is that Metis must receive a discovery packet before it will wake up and respond to the start packet (unless Phil has changed the firmware since I last looked).  Either way, if you're not bridging, I'm really surprised Metis is responding to your pings.  Metis doesn't have a full TCP/IP stack, so it needs to be on the same L2 segment as the computer controlling it.  You can't specify a default route on Metis because it has no idea of a routing table or anything, it just knows from what address the start packet originated, and pushes packets to that destination.  There's not even really any ARP at all either, it just pays attention to the MAC addresses of the machines that it talks to.

So, you may be doing something cute with proxy arp and such that may be making the ping work.  This may work in practice once you can get the connection going, but I'm not really sure if this is an optimal case.  It certainly wasn't envisioned as something we were supporting the rudimentary Metis IP stack was written.  John's been looking at writing a Metis firmware such that it's a bit smarter, but I haven't seem how his struggles are going with that.

Incidentally, I've tested Metis over my Airport Extreme with my MacBook Pro on 802.11n and it works fine.  I haven't tried scaling back to 802.11g, but I honestly don't think there will be a huge issue for single hardware/firmware receiver applications.  The data rate is well less than 10Mbit/sec in that case.

> Mark - K4XML

--
Jeremy McDermond (NH6Z)
Xenotropic Systems
mcdermj at xenotropic.com



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