NMEA weirdness on ICOM M323

VHF Marine Band radios, protocol, radio communication theory, practical advice; AIS; DSC; MMSI; EPIRB.
gaffer206
Posts: 4
Joined: Sun Jun 30, 2019 3:59 am

NMEA weirdness on ICOM M323

Postby gaffer206 » Sun Jun 30, 2019 4:05 am

I have my ICOM IC-M323 radio wired to a USB serial adaptor driven by the Chrome NMEA SImulator, and I'm monitoring the serial port.

The ICOM M323 is set to output GPS data received on its input to its output.

I can see the DSC and GPS data coming out of the M-323.

If I stop the simulator the GPS output from the radio stops.

If I start the simulator the GPS output from the radio starts.

So the radio is definitely receiving GPS data in real time on its input.

But the radio display says NO POSITION NO TIME.

Is this a faulty radio?

jimh
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Re: NMEA weirdness on ICOM M323

Postby jimh » Sun Jun 30, 2019 8:09 am

The ICOM M323 radio may be very particular about which NMEA-0183 sentence it must receive in order be provided with time and position information. Try sending various sentences, RMC, GAA, GLL, and so on.

I found an older ICOM radio would only accept one specific sentence.

See:

viewtopic.php?f=13&t=4087&p=23075


Also, the M323 radio may be particular about the device type information in the sentence, the TALKER ID, expecting only a specific prefix, such as “GP.” See

http://freenmea.net/docs

gaffer206
Posts: 4
Joined: Sun Jun 30, 2019 3:59 am

Re: NMEA weirdness on ICOM M323

Postby gaffer206 » Sun Jun 30, 2019 10:45 am

Thanks Jim,

It could be but probably not.

I should have said that earlier I did see it picking up time and position, but pretty much ONLY on power on. Now it doesn't even do that.

FYI this is an example of what the simulator sends:

$GPRMC,144433.892,A,5300.02,N,00059.97,W,13.0,36.8,300619,,,*3F
$IIVHW,36.8,T,36.8,M,6.7,N,12.4,K*63
$IIHDT,36.8,T*1F
$GPGLL,5300.02,N,00059.97,W,144433.892,A*26
$GPGGA,144433.892,5300.02,N,00059.97,W,1,4,4.2,2.0,M,,,,*2D
$GPGSA,A,3,8,11,15,22,,,,,,,,,1.8,4.2,3.7*05
$GPZDA,144433.892,30,06,2019,+01,00*75
!AIVDO,1,1,,A,17PaewhP22wsK<`NDsaiL1920000,0*2D
$WIMWV,360.0,T,39.8,N,A*12
$WIMWD,360.0,T,360.0,M,39.8,N,20.5,M*5F
$WIMWV,332.0,R,50.8,N,A*1C
$IIMTW,7.6,C*22
$SDDPT,20.3,01*49
$SDDBT,66.6,f,20.3,M,11.1,F*30
$SDDBK,66.6,f,20.3,M,11.1,F*2F
$SDDBS,66.6,f,20.3,M,11.1,F*37

So the only relevant missing sentence is RMC.

And this is what the radio emits when it has simulator input:

$PICOA,15,00,DSC,LNK,2351093660,V*14
$CDRMC,080743.618,A,5300.20,N,00059.67,W,32.9,42.6,300619,,,*26
$CDGLL,5300.20,N,00059.67,W,080743.618,A*38
$CDGGA,080743.618,5300.20,N,00059.67,W,1,4,1.8,2.0,M,,,,*3C
$CDGSA,A,3,8,11,15,22,,,,,,,,,1.5,1.8,2.4*15

gaffer206
Posts: 4
Joined: Sun Jun 30, 2019 3:59 am

Re: NMEA weirdness on ICOM M323

Postby gaffer206 » Sun Jun 30, 2019 10:58 am

Ah,

I just sent a text file containing

$GPGLL,5300.02,N,00059.97,W,144433.892,A*26
$GPGGA,144433.892,5300.02,N,00059.97,W,1,4,4.2,2.0,M,,,,*2D
$GPGSA,A,3,8,11,15,22,,,,,,,,,1.8,4.2,3.7*05
$GPZDA,144433.892,30,06,2019,+01,00*75

to /dev/ttyUSB0 and the radio is showing time and position.

So it seems to be the sentences it doesn't like that's messing it up.

I'll try some filtering using kplex.

gaffer206
Posts: 4
Joined: Sun Jun 30, 2019 3:59 am

Re: NMEA weirdness on ICOM M323

Postby gaffer206 » Sun Jun 30, 2019 11:13 am

That [i.e., the sentences being sent by the simulator to the M323 that the M323 doesn't seem to be able to handle] was [the cause of the problem] . [The ICOM M323 radio] is now working [that is, it now is able to get the GPS data from the simulator via NMEA-0183].

I've moved the simulator so it serves on a TCP port and inserted kplex with the following configuration and position and time are now updating nicely:

[serial]
filename=/dev/ttyUSB0
direction=out
baud=4800
ofilter=+GPGLL:-all
[tcp]
mode=client
address=localhost
port=55555
direction=in

jimh
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Location: Michigan, Lower Peninsula
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Re: NMEA weirdness on ICOM M323

Postby jimh » Sun Jun 30, 2019 2:30 pm

Maybe the checksum was missing or wrong from the simulator. Some NMEA-0183 devices may be lax about the checksum in a sentence, and others may be strict. The radio might have been ignoring sentences with bad checksums.

jimh
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Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
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Re: NMEA weirdness on ICOM M323

Postby jimh » Sun Jun 30, 2019 2:38 pm

By any chance are you running kplex on MacOS?