[USRP-users] Keep One in N

Zhihong Luo zhluo at umich.edu
Tue Mar 29 17:52:26 EDT 2016


Hi Jonathon,

I realized the reason after noticing the i_tlast on the if condition,
thanks for pointing it out.

But I may need sample based keep one in n. Can I do it by simply removing
the i_tlast? Is there some potential issues that I overlook?

Thanks,
Zhihong






On Mon, Mar 28, 2016 at 12:45 PM, Jonathon Pendlum <
jonathon.pendlum at ettus.com> wrote:

> Hi Zhihong,
>
> The keep one in n block drops packets and not individual samples. So in
> other words, if N=2 it will drop every other packet, not every other sample.
>
>
>
> Jonathon
>
> On Sat, Mar 26, 2016 at 10:44 PM, Zhihong Luo via USRP-users <
> usrp-users at lists.ettus.com> wrote:
>
>> Hi all,
>>
>> I tried to use the RFNoC FIR filter and Keep One in N blocks to decimate
>> my received signal. The FIR filter worked fine, but the Keep One in N block
>> did not work as I expected. When capturing a square signal, with and
>> without the Keep One in N block, the received sample number of the high
>> period remained unchanged. I wonder whether I made a mistake in my code:
>>
>>  uhd::rfnoc::block_id_t fir_ctrl_id(0, "FIR", 0);
>>  uhd::rfnoc::block_id_t keep_n_id(0,"KeepOneInN",0);
>>
>>  uhd::rfnoc::fir_block_ctrl::sptr fir_ctrl =
>> usrp->get_device3()->find_block_ctrl<uhd::rfnoc::fir_block_ctrl>(fir_ctrl_id);
>>
>> uhd::rfnoc::block_ctrl_base::sptr
>> keep_n_ctrl=usrp->get_device3()->find_block_ctrl(keep_n_id);
>>
>>  fir_ctrl->set_args(uhd::device_addr_t(streamargs)); //streamargs is an
>> empty string
>>  usrp->get_device3()->get_block_ctrl(radio_ctrl_id)->set_args(streamargs);
>>  keep_n_ctrl->set_args(uhd::device_addr_t(streamargs));
>>
>>  fir_ctrl->set_taps(taps);
>>  keep_n_ctrl->sr_write("SR_N", 16); // downsampling by 16 times
>>
>> usrp->connect(radio_ctrl_id, fir_ctrl->get_block_id());
>> usrp->connect(fir_ctrl->get_block_id(),  keep_n_ctrl->get_block_id());
>>
>> usrp->set_rx_channel(keep_n_ctrl->get_block_id());
>>
>> Thanks in advance for providing any help :)
>>
>> Zhihong
>>
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>> USRP-users at lists.ettus.com
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>>
>>
>
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