Hi Marcus
Thank you for the response. I will take your advice and go over all the
tutorial information again as well as [2] & [3].
However I have completed the tutorial's and for the most part understand
the information. Admittedly I am still struggling with the use of stream
tag's, I have gone back over the tutorial on stream tags multiple times and
whilst I understand how to create stream tags and their propagation, I
haven't really grasped how and when to use them. I have also read [2] but
don't really understand how this will help me.
Please excuse my lack of understanding. Are you suggesting that I send a
SOB tag along with the Flag 0x7E (1 byte) and the radio will continuously
output 0x7E's until I send an EOB ?
The project I am on is a cubesat project and the team working on the
cubesat have stipulated that to maintain lock on the signal, when not
transmitting data the ground station transmitter (my work) is to send
continuous HDLC Flags. So regardless of my view I need to somehow meet this
requirement.
Sorry for taking up so much of your time. Your assistance is appreciated.
Kind Regards
Frank
On 15 August 2016 at 20:24, Marcus Müller-3 [via GnuRadio] <
[email protected]> wrote:
> Hi Frank,
>
> really, with the advances of the drivers and hardware capability and the
> changes in GNU Radio architecture, your problem isn't that comparable to
> the problem in 2009; again, please don't rely on Nabble posts; Nabble is
> just a mirror of the GNU mailing list archives (and adds some kind of forum
> infrastructure), and it has been down lately for quite some time. I don't
> trust it, personally, and usually urge people to directly sign up to the
> mailing list and use the official archives; so here's the link to the
> official mailing list archive's thread:
>
> http://lists.gnu.org/archive/html/discuss-gnuradio/2009-03/msg00552.html
>
> Anyway, let us really discard the idea of describing your problem in terms
> of a problem from 2009; that just makes things more complicated, because
> then I'd have to explain what happened to GNU Radio in the last seven
> years, and why Ettus N210 & B210 driven via gr-uhd isn't like a USRP1
> driven via libusrp. What you're really asking is analogous to "my 2012
> Ferrari won't start; I found this 1920 Ford Model T hand crank start
> discussion, but I can't find the hand crank in my Ferrari's trunk". Things
> simply don't work like that anymore.
>
> So, this has really become much easier: The USRP sink reads stream tags,
> which can contain a start-of-burst, and a end-of-burst info; the N210 and
> B210 USRPs (unlike what was available in 2009) keep an internal device
> time, so that they can even be used to transmit samples at a specified
> time, without having to continuously send before that time.
>
> It's important to understand the concept of stream tags to work with this
> (that concept wasn't around in 2009 in the shape that it's built into GNU
> Radio since roughly 2011), so I'm referring you to the official GNU Radio
> tutorials [1].
>
> Chapter 5 should explain Tags and Message Passing, but the tutorial
> chapters built atop of the previous ones, so I'd recommend starting with
> the first and working to the fifth; you will be rewarded with being able to
> fully understand Chapter 6, which is about interfacing what you've built in
> chapters 1-4 with real USRP hardware, and with an instant understanding of
> [2], the documentation of how to send "bursty" samples to the USRP via
> stream tags!
>
> For a demo of how to use stream tags to tune at a specific time and
> annotate, see [3]; if you run that as
>
> ./freq_hopping.py -r 2.5e5 -N 10000 -t 500 -f 2.4e9 -c 100 -d 2.5e6 -v
>
> with your B210 attached, you should see its TX LED blink *exactly* twice
> per second.
>
> Best regards,
>
> Marcus
> [1] http://tutorials.gnuradio.org
> [2] http://gnuradio.org/doc/doxygen/classgr_1_1uhd_1_1usrp__sink.html
> [3] https://github.com/gnuradio/gnuradio/blob/v3.7.10.1/gr-
> uhd/examples/python/freq_hopping.py
>
> On 15.08.2016 13:07, Inspire Me wrote:
>
> Hi Marcus
>
> My apologies if I posted incorrectly, I am new to this. Thank you for
> responding.
> The posts I was referring to are http://gnuradio.4.n7.
> nabble.com/Constant-carrier-digital-transmission-td27764.html
>
>
> I do understand that things have moved on since 2009. I was hoping to have
> a look at the code mentioned in the post for the
> GMSKSpacecraftGroundstation. https://moo.cmcl.cs.cmu.edu/trac/cgran/wiki/
> GMSKSpacecraftGroundstation I have not been able to find it. I was
> wanting to see how it was done.
>
> I have the almost the identical situation described in the post. I was
> thinking I need a Flag Source feeding some sort of switch logic that checks
> if no message is present on the data stream input and then selects the flag
> input, sends one flag; repeats check and send until a data arrives on the
> data stream input.
>
> We are currently using Ettus N210 & B210 hardware. I have a Tx chain
> working except for the flag stuff. For testing I have Mux'd in a vector of
> flags (0x7E) and can successfully talk to the receive end.
>
> Any help would be greatly appreciated.
>
> Kind Regards
> Frank
>
>
> On 15 August 2016 at 20:29, Marcus Müller <[hidden email]
> <http:///user/SendEmail.jtp?type=node&node=61221&i=0>> wrote:
>
>> Hi Frank,
>>
>> **which** post from March 2009? Would you happen to have a mailing list
>> archive [1] link (please don't use Nabble).
>>
>> At any rate, what applied 7 years ago regarding messages will probably
>> not apply now, anymore.
>>
>> I think it would be very worthwhile if we didn't discuss this based on
>> something from 2009; what program/flowgraph/python script are you
>> specifically looking at?
>>
>> Best regards,
>> Marcus
>>
>>
>> [1] http://lists.gnu.org/archive/html/discuss-gnuradio/2009-03/index.html
>> On 15.08.2016 10:41, Inspire wrote:
>> > Hello
>> >
>> > I am relatively new to gnuradio, I have only been working with it for 6
>> > weeks.
>> >
>> > I came across your posts from march 2009 relating to continuously
>> > transmitting 0x7E's when no messages are present in the queue. I am
>> facing
>> > the exact issue with our implementation in GNURadio. I need to send out
>> > continuous flags when no messages are in the queue but immediately
>> (within a
>> > few flags) switch to sending data when a message arrives. I have gone
>> > looking for the HDLC Source code spoken about but have not found it.
>> >
>> > Q1. How was this solved ?
>> >
>> > I am struggling with getting my head around how to ensure the continuous
>> > stream of Flags given that gnuradio buffers up and schedules
>> transmission
>> > based on buffers. I am also struggling with how to do the switching
>> between
>> > streams.
>> >
>> > I know 2009 was a long time ago, but any help would be greatly
>> appreciated.
>> > The mentioned source code example or any other example code would be of
>> > great benefit as GNURadio documentation is confusing and some times
>> > non-existent.
>> >
>> > Kind Regards
>> > Frank
>> >
>> >
>> >
>> > --
>> > View this message in context: http://gnuradio.4.n7.nabble.co
>> m/Constant-carrier-digital-transmission-tp27764p61217.html
>> > Sent from the GnuRadio mailing list archive at Nabble.com.
>> >
>> > _______________________________________________
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