[chirp_devel] Radioddity FS-T3 seems related to Retevis RB18

[Charles Terrell]

Trying to get Chirp to talk to my Radioddity FS-T3 (same as PR-T3).
Using a typical USB cable with FTDI chip. Proprietary software from
Radioddity runs well in Win 10, and tolerably in Fedora using
"bottles". Using plain wine is more complicated due to .net DLL
errors. Based on earlier FCC filings and similar appearance, it could
be a rebadged Baofeng BF-T12.

Could not find a free working serial port capture solution for Win 10.
Linux capture scripts from chirp docs yielded a pcap file but nothing
parsed out. Finally just loaded the pcap file into wireshark.
Confirmed baud and flow settings. Exported as plain text from there,
grepped for "payload", cleaned it up with my own perl script.

What I found: PC sends "PROGRAL" and radio replies with "P3107".
Digging through existing chirp code, Retevis RB18 driver
(radtel_t18.py) has both PROGRAL and P3107.

Tried it: Yes! Radioddity FS-T3 actually works with RB18 driver. But
it's not perfect. It's limited to 22 channels, while the real radio
can handle up to 99 memory channels. 22 seems to be hard-coded in the
RB18 driver. This is sort of a big deal because the radio offers no
way to change squelch tones / codes without using a computer.
Sometimes it's easier just to add another channel for a particular
group or event.

Also, the radio can do separate RX/TX freqs via its original software,
making it GMRS repeater compatible. (Note that it is not marketed as
GMRS. Based on signal reports, I suspect it forces narrowband for GMRS
repeaters. Possibly because repeater inputs are in the same general
freq range as FRS channels 8-14.) But the RB18 driver forces simplex.

Haven't tried other drivers yet, but at least 3 other files mention
P3107. This is a good start though. As it is now, the RB18 driver
gives the functionality one would need for pure FRS-only usage. I
think we can do better for GMRS / PMR446 / 70cm ham / extra FRS
channels, which the mfg's software already can do.

I'll check my dev tools setup and see what I can come up with.

----
Charles Terrell <tachyon at pobox.com>