Re: [Discuss-gnuradio] packet_pad_impl in gr-foo

[Nikita Airee]

I sorry that I was not very clear. The Packet Pad2 block works just fine. I meant the Packet Pad block. When that block is placed before the UHD sink, nothing is transmitted. Tag Debug also doesn't show any added tags.

On Fri, Mar 3, 2017 at 1:16 PM, Bastian Bloessl <address@hidden> wrote:

Hi,


> On 3 Mar 2017, at 07:15, Nikita Airee <address@hidden> wrote:
>
> I would like to time synchronize transmission in two USRPs. I understand that after synchronizing pps and 10MHz, I would have to make use of time tags. For that I looked to packet_pad_impl in gr-foo.
>
> When I use the block with a flowgraph, specifically the example flowgraphs in gr-ieee802-11, it really just blocks the transmission, meaning no data is transmitted from the USRP. The loopback too doesn't work. Tag debug also doesn't show the presence of any tags(tx_eob, tx_sob, tx_time etc).
>
> Is the block not working or am I doing something wrong? If at all I completely misunderstood the purpose of the block, could you please point me in the right direction for implementing time tags as well?

I don’t get what you mean. Could you please describe a bit more detailed what’s happening.

The gr-ieee802-11 flow graph uses “Packet Pad 2”, a Tagged Stream Block that just pads some 0s. It doesn’t block. When you enable the delay option, it will add a “tx_time” tag that can be used to delay the transmission. (The delay is added by the USRP, i.e., also in that case it doesn’t block).

Best,
Bastian