[Linrad] Re: RX OVERRUN_ERROR cause: "Visual Effects" (Ubuntu)

[Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>]

Hi Thomas,

> However, the SDR-IQ Interface Specification Ver. 1.00 of Dec 16,2006 on
> page 9, says it is "USB 2.0 Full Speed".  The RFspace web paqge also
> describes it as a USB 2.0 device.
> 
> For the SDR-IQ,
> # lsusb -v -d 0403:6001,
> ...
> bcdUSB               2.00
> ...
> 
> For a pl2303 serial device
> # lsusb -v -d 0557:2008
> ...
> bcdUSB               1.10
> ...
> 
> Is there something in the PIC that limits this?

I do not have an SDR-IQ, I only have an SDR-14. The SDR-14 is
max 180 kHz or so according to RFspace specifications. 
Based on experience a long time ago I have set a limit at 260 kHz.
The highest speed I could use on my Pentium 4 was about 130 kHz.

I made a test today - and now I can run the SDR-14 at 222 kHz
without any problems so I have changed the limit to 500 kHz.

In Linrad-03.07 it is a define in sdr14.c:
#define MAX_SDR14_SPEED 500000

I do not know exactly what changes that have made it possible to
run the USB faster, it could be a more modern kernel or something
I did in Linrad. Anyway, the speed is now much higher than expected:-)

Please change 260000 and 300000 in sdr14.c at lines 507 and 880 to 
something higher and check where the limit is for SDR-IQ on your
computer. In case it is much above 250 kHz I will make the
tests different for SDR-14 and SDR-IQ.

(Old Linrad versions did not check the nominal speed and much
too high values caused hard to understand crashes for newcomers.)

73

Leif / SM5BSZ


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