Support for AirSpy MINI

[istamov]

Hello,

First of all - thank you for your efforts in developing this great software. Is it possible to also add support for AirSpy MINI - it differs from the regular AirSpy R2 in terms of the supported sample rates:

### Regular AirSpy R2
Board ID Number: 0 (AIRSPY)
Firmware Version: AirSpy NOS v1.0.0-rc10-3-g7120e77 2018-04-28
Supported sample rates:
    10.000000 MSPS
    2.500000 MSPS

### AirSpy MINI
Board ID Number: 0 (AIRSPY)
Firmware Version: AirSpy MINI v1.0.0-rc10-3-g7120e77 2018-04-28
Supported sample rates:
    6.000000 MSPS
    3.000000 MSPS

I was able to compile and run vdlm2dec by changing SDRINRATE in file "vdlm2.h" from "5000000" to "6000000", but not sure this is the only change that is needed.

#ifdef WITH_AIR
#define SDRINRATE 6000000
#define SDRCLK  1250
#endif

Thanks in advance!

[TLeconte]

No I will not be sufficient. I will try to think about a solution, but I will not be able to test it, and :

no tested, does not work

[istamov]

No problem if you need any testing for the new code or even remote access to an RPi3 with the AirSpy MINI attached. But if it will be too much of a rework, I will just try to get an AirSpy R2 to replace the MINI.

[TLeconte]

Try :

define SDRINRATE 3000000

define SDRCLK 750

and in function chooseFc (air.c) comment the 2 lines with _airspy_r820twrite

[istamov]

Tried with the following changes:

In file "vdlm2.h":

#ifdef WITH_AIR
#define SDRINRATE 3000000
#define SDRCLK 750
#endif

In file "air.c":

static unsigned int chooseFc(unsigned int minF,unsigned int maxF)
{
        unsigned int bw=maxF-minF+2*STEPRATE;
        unsigned int off;
        int i,j;

        for(i=7;i>=0;i--)
                if((r820t_hf[5]-r820t_lf[i])>=bw) break;
        if(i<0) return 0;

        for(j=5;j>=0;j--)
                if((r820t_hf[j]-r820t_lf[i])<=bw) break;
        j++;

        off=(r820t_hf[j]+r820t_lf[i])/2-SDRINRATE/4;

        //airspy_r820t_write(device, 10, 0xB0 | (15-j));
        //airspy_r820t_write(device, 11, 0xE0 | (15-i));

        return((maxF+minF)/2+off);
}

But the result is as before:

$ ./vdlm2dec -v -U -E -G 136.875 136.975
did not find needed sampling rate
Unable to init input

[TLeconte]

My bad. try with

ifdef WITH_AIR

define SDRINRATE 6000000

define SDRCLK 1500

endif

and keep the commants

[istamov]

Thank you, that seems to do the trick (changing the defines and commenting the "airspy_r820t_write" lines), now I receive messages:

$ ./vdlm2dec -v -U -E -G 136.725 136.775 136.825 136.875 136.975
Set freq. to 137223862 hz

[#5 (F:136.975 P:1.7) 26/09/2018 17:59:52.472 --------------------------------
Response from Aircraft:4B9061 (airborne) to GroundD:29BCD8 
Frame-S: Nr:6 RR

[#5 (F:136.975 P:3.0) 26/09/2018 17:59:55.687 --------------------------------
Command from Aircraft:406D8E (airborne) to GroundD:1091AA 
Frame-I: Ns:0 Nr:1
unknown data
1b ff ca 1e 28 f6 40 00 f7 85 00 1e 04 00 00 00    |....(.@.........|
04 00 00 00 02 03 04 bc 5c d9 31 b4 da 00 39 3b    |........\.1...9;|
90 20 9f 2e d8 48 08                               |. ...H..........|

[#5 (F:136.975 P:3.1) 26/09/2018 17:59:56.502 --------------------------------
Response from Aircraft:406D8E (airborne) to GroundD:1091AA 
Frame-S: Nr:2 RR

[TLeconte]

Great, I will try to explain all that in the README

[TLeconte]

Do you have an adsb antenna ? I wrote an adsb decoder for airspy R2 https://github.com/TLeconte/adsbdec

It could work for airspy mini with some modifications. If you could test, I will do the mods .

[istamov]

The MINI is on a remote site currently connected to a wideband Diamond D-130NJ discone antenna, but I guess it will still receive some ADS-B signals. If you are not in a hurry, I can visit the place in about a week and attach an ADS-B optimised antenna (FlightAware 5.5 dBi) to it, so we can test how it performs.

[TLeconte]

OK, that's great. No hurry at all. I have to do the mods before, but I wanted to be sure that someone could test them.

[TLeconte]

OK I just have committed changes for airspy mini. When you will get the time :

• Get the last version
• add -D AIRSPY_MINI to the CFLAGS in Makefile
• make clean
• make

GIve your results in Issue of adsbdec

Thanks

[istamov]

Thanks, I have tried the latest git (by the way it shows the last modification as 3 days ago?), but I still get "did not find needed sampling rate".

I have reported the full command output in the issue opened by @papasven, where he has also provided more details.