hackrf: gr-osmocom sink tx buffering

Eric Wild ewild at sysmocom.de
Wed Dec 9 15:39:55 UTC 2020


Hi Sebastian,
since the hackrf is half-duplex and has no timestamp support (only 
continuous streaming) the buffer size was chosen at the time to provide 
a reasonable tradeoff between latency and performance for higher sample 
rates - I suppose you could just decrease it if that is the problem, but 
there is still no way to just send something immediately, there will 
always be a considerable latency between the host and the rf output.

-Eric

Am 09.12.2020 um 13:23 schrieb Sebastian Böhm:
>
> Does anyone have any idea what could be the reason for this behavior?
>
> Am 01.12.2020 um 16:28 schrieb Sebastian Böhm:
>> Hi,
>>
>> i try to transmit 2.48 ghz radio packets (beacons) at a fixed time 
>> interval (e.g. every 1 s) via hackrf using the osmocom sink in 
>> gnuradio. Without exception, the beacons are all received by my 
>> sniffer "golden device" hardware, but burst.
>>
>> It seems that the packets are only transferred via USB to the hackrf 
>> device hardware when the buffer with the fixed BUF_LEN 262144 
>> (32*16*512) is completely filled. For my setup this are e.g. 18 
>> beacon frames, which are transmitted as burst. When I look at the USB 
>> interface, I can see this burst of data every 18 seconds in a full 
>> USB request block (URB) of  size 262144 byte. All other URBs (also of 
>> size 262144 - every approx. 200us) transferred via USB are filled 
>> with zeros only. So this burst behavior should be caused by gnuradio.
>>
>> How can I achieve that the complex data of the osmocom sink's input 
>> is immediately (with the next URB) transferred to the hackrf 
>> hardware? Am I missing any options of the GRC module?
>>
>> Thank You in advance!
>>
>> Regards,
>> Sebastian
>> -- 
>> __________________________________________________________
>>
>> Sebastian Boehm
>> Brandenburg University of Technology Cottbus - Senftenberg
>> Computer Networks Communication Systems Group
>>
>> E-Mail: sebastian.boehm at b-tu.de <mailto:Sebastian.Boehm at b-tu.de>
>>
>> P.O. Box: 10 13 44
>> D-03013 Cottbus
>> GERMANY


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