[Hackrf-dev] hackrf_transfer receives 1kB (at most) of valid data

[Brent Thorne]

Hey Dominic,

Thanks for the explanation on all points!  Yes the band at 900Mhz is
rather quiet.  Using your suggesting of tuning to a local FM station
made the hex values more visually modulated, also it helps to know
these values are signed 8 bit values.  Right on!   Now back to the
lesson plan.

Thanks again,

Brent

On Fri, Feb 12, 2016 at 2:52 AM, Dominic Spill <dominicgs at gmail.com> wrote:
> On 12 February 2016 at 06:43, Brent Thorne <brentathorne at gmail.com> wrote:
>>
>> Got to lesson 5 in the tutorial and I think I broke something after
>> upgrading to hackrf-2015.07.2 (firmware and cpld images) .  I can only
>> capture 1kB using 'hackrf_transfer -r'.  Help me understand if I'm
>> doing something wrong.
>>
>> $ hackrf_info
>> Found HackRF board 0:
>> Board ID Number: 2 (HackRF One)
>> Firmware Version: 2015.07.2
>
> Looks good.  You could also upgrade the CPLD too but if you're coming
> from the 2014.08.1 release there's no need because there was no
> change.
>
>> 19.9 MiB / 1.000 sec = 19.9 MiB/second
>> 19.9 MiB / 1.000 sec = 19.9 MiB/second
>> 19.9 MiB / 1.000 sec = 19.9 MiB/second
>> ^CCaught signal 2
>>  4.7 MiB / 0.224 sec = 21.1 MiB/second
>
> This looks like it transferred much more than 1kB.  How big is the
> rx.raw output file?
>
>> $ hexdump rx.raw | head -10
>> 0000000 ff00 ffff ff00 ff00 ff00 ff00 0000 ff00
>> 0000010 ff00 ff00 ff00 ff00 0000 ffff ff00 ffff
>> 0000020 fe00 ff00 ff00 ff00 ff00 ff00 ffff ff00
>> 0000030 ffff ff00 ff00 ff00 ff00 0000 ff00 0000
>> 0000040 ff00 ff00 fe00 ff00 ff00 ff00 ff00 ff00
>> 0000050 ff00 ff00 ff00 ff00 fe00 ff00 ff00 fe00
>> 0000060 0000 ff00 ff00 ff00 ff00 ff00 ff00 ff00
>> 0000070 ff00 ff00 ff00 ff00 ff00 fe00 ff00 ff00
>> 0000080 ff00 ff00 ff00 0000 ff00 ff00 ff00 ff00
>> 0000090 ffff ff00 ff00 ff00 ffff ff00 ff00 ff00
>
> These values are signed int8s, which means what you're seeing here are
> very low values, fluctuating around zero.  This looks like valid data
> to me.
>
> This brings us back to the command that you're using to capture the data:
>
>> $ hackrf_transfer -r rx.raw
>
> You will probably see more interesting data if you set some gain
> levels and perhaps start out by tuning to a local FM station
> frequency.  -l -g set gain levels, -a enables the amplifier (although
> I usually leave it off unless I need it) and -f will let you set the
> frequency.  I would expect you to see much more interesting data if
> you set these.
>
> Please let me know how you get on with this.
>
> Thanks,
>   Dominic