[Dprglist] Roborama & wireless networking

Carl Ott carl.ott.jr at gmail.com
Sun May 13 15:33:16 PDT 2018

Hey all - thanks for the ideas!

Doug and John -

I'm intrigued by the 433 MHz Wixels - but sounds like they offer a serial
port connection.  To use anything like that I'd need to put additional code
at both ends, to convert the existing https / REST based API into a serial
port interface.  On the commands to robot side, I'm trying to avoid that
and stick with something over a network - https / MQTT / AMQP /
web-sockets, etc...

Bluetooth might also work for commands, except that's also in the 2.4 GHz
band, with significant overlap with Wi-Fi.  I haven't attempted to quantify
it, but I wouldn't be surprised if it suffers a similar fate as Wi-Fi.  But
BT is definitely in the toolkit - I have some pucks and tools well suited
to going there...  Also, I'm pretty sure that  BT is too low bandwidth &
not well suited for video...  On the plus side, there do seem to be plenty
of libraries e.g. for node.js to control and listen to bluetooth devices...

The home video senders are likely too big - although there are some battery
powered video links meant for spying.  The biggest issue I have with those,
is that I believe they tend to send video with it's own modulation scheme -
which would likely require a different camera interface than the ones which
plug right into an R-Pi.  Also, on the receiving end, they need to be
demodulated and digitized with the stream fed into video processing.

I'm thinking it'll be easier to solve the video issue with a network /
packet based approach.  Also, using a network connection for both video
feed and commands to robot requires just one common interface, versus a
couple of very different interfaces.

But if there was a way to get network packets over Wixels... sounds like a
worthy search...


thanks for the HAM link.  I had found some earlier HAM related stuff like
that, but those look like current references.

The nice thing about HAM, or maybe also wixels, is that it could give a
chance for a solution that could work over nice distances outdoors as well
- likely further than Wi-Fi.  And I have a decent HAM license, earned a
year or two ago - would be nice to leverage it and snag lightly used
spectrum after putting the trouble into getting a license...

Thanks all - keep the ideas coming!


On Sun, May 13, 2018 at 3:02 PM, Mary Mathias <mjmmaker at gmail.com> wrote:

> Oh.. he also said lots of local hams, especially those doing emergency
> communication, are working on it, so maybe we can find a local group either
> there at DMS or on Carrollton to help?
> ~MJ
> On Sun, May 13, 2018, 2:48 PM Mary Mathias <mjmmaker at gmail.com> wrote:
>> Carl,
>> I asked one of my old-time DFW Makers who taught HAM classes for us & he
>> suggests starting here https://www.aredn.org
>> for packet radio and mesh networking over ham frequencies.
>> ~Mary
>> On May 13, 2018 1:26 PM, "Carl Ott via DPRGlist" <dprglist at lists.dprg.org>
>> wrote:
>> Thanks to everybody who came to RoboRama yesterday - it seems that
>> everybody had a good time, we met new visitors & old friends, and we had a
>> well received contest!
>> We also had Wi-Fi issues - leading to questions...
>> Can anybody offer suggestions for the Wi-Fi issue some of us observed
>> yesterday?
>> The issue was that as the day went on, and more people surfaced in the
>> Makerspace, the Wi-Fi environment went from almost tolerable to
>> ***difficult for some - won't work at all for others***.
>> This forced several of us to use personal access points - which
>> definitely helped - at least for those using the connection more for
>> telemetry than 'in the loop communication'.  However, I was not able to run
>> at all due to apparently tight latency/jitter requirements, which became
>> unmet as the makerspace filled up.  This becomes apparent for my robot when
>> one video stream receiver (whatever Chrome uses) behaves much better and
>> more consistently as the environment degrades (still ultimately failing),
>> but another codec viewing the same stream (ffmpeg + whatever plug-in
>> adapter RoboRealm uses for RTSP) fails much sooner - 'at the drop of a hat
>> / network-packet' - completely breaking my control loop, yielding grumpy
>> scowls and a very still and boring robot...
>> My question is this - what options should I consider beyond the obvious?
>> *The obvious options are*
>> a) keep processing local, get the network out of the loop
>> b) flip the personal access point an unused Wi-Fi channel
>> ---> e.g. on 5 GHz
>> ---> ie. requiring adding a 5 GHz dongle to R-Pi Zero W (depends on
>> finding one with compatible driver)
>> ---> or requiring swapping R-Pi Zero for e.g.R-Pi 3 B+ (with built-in 5
>> GHz, entails considerably more hardware rework to existing robot platform)
>> c) find an alternate radio strategy
>> d) give up
>> Currently, options a and d are off the table, and next steps focus on
>> option b.
>> *So my questions for DPRG land:*
>> *1. for option b:* can anybody recommend an R-Pi Zero W compatible Wi-Fi
>> dongle with 5 GHz?   If no better out there, I'm gonna try an older /
>> slightly larger version of this: https://www.amazon.com/g
>> p/product/B01MY7PL10/ref=ox_sc_mini_detail?ie=UTF8&psc=1&smi
>> d=ATVPDKIKX0DER, with what appears to be a R-Pi compatible open source
>> driver recommended by the vendor...
>> *2. **for option c:*  can anybody recommend something small other than
>> Wi-Fi that can carry low jitter / low latency /  low video resolution
>> (e.g. 160 x 120)  network packets, and interface cleanly to both R-Pi
>> Zero and Windows?
>> *3. **for option c:*  has anybody dabbled with network packet data over
>> HAM frequencies?
>> Thanks!
>> Carl
>> carl.ott.jr at gmail.com
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