FLDIGI on the Raspberry Pi / Getting Better

FLDIGI is a great software package that uses lots of processing to convert the analog signal into the streams of characters and files for the user.  With that conversion comes the cost of processing power.

Ideally, you should run FLDIGI on a computer with a microprocessor speed of 1 Ghz or greater.  The Raspberry Pi only runs at 700 Mhz, so it has typically been overlooked or even discouraged as a platform for FLDIGI.

As I stated in the November 22nd training session, my past experiences with FLDIGI on the Raspberry Pi were mixed.  It typically maxed out the processor and was sometimes unstable.  Early attempts to use sound cards with the Raspberry Pi were also less than ideal, as the early soundcard drivers in Raspberian had difficulties with normal day-to-day audio, let alone modes that require high linearity.  Early versions suffered from snap-crackle-pop sounds on both the output and input (if you used an external USB soundcard), which usually brought experiments in something like FLDIGI to a quick end.

I am pleased to report that the sound card drivers are more robust, plus the hardware solution of an SYBA SD-CM-UAUD has very low background sound levels and appears to get along with Raspberian very well, as evidenced by work by persons on the Dire Wolf APRS project.

So, I used this morning to revisit FLDIGI on the Raspberry Pi.  I took a new Raspberian SD card, booted up, and entered "apt-get FLDIGI".  Within 20 minutes I had FLDIGI and FLARQ icons in the Ham Radio program group.

The version of FLDIGI that is currently available via apt-get is several versions behind, so it does not have all the latest updates, like PSK-500, PSK-1000, or the KISS port.

So, I decided to connect the SYBA soundcard to my laptop (which is running the latest windows version of FLDIGI).  Audio out to audio in on both sides.

After trying to run PSK-250 with some lockups, I decided to drop to PSK-125.



FLDIGI and FLARQ running side-by-side on the Pi

I was able to transfer several files between the two computers using FLARQ with no lockups or problems.  In fact, I didn't have any errors on either side.  Of course, all of this was with a "perfect" audio cable, as opposed to a radio-to-radio connection.  However, it was a much better experience than what I had almost a year ago performing the same experiment.

There is a way to recompile the latest version of FLDIGI, FLARQ, FLMSG, and FLAMP on the Raspberry Pi.  If you would like an SD card with all four on them, please comment below and I will go ahead and make some cards up (assuming there is interest).



Close-up of FLDIGI on the Pi



Close-up of FLARQ on the Pi