FURUNO FCV668 sounder

Discussion and support for the Nmea4Wifi multiplexer - a 4-input Nmea 0183 wifi multiplexer.
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schnapsy
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FURUNO FCV668 sounder

Post by schnapsy » Sun Oct 20, 2019 5:17 pm

Hello Luis,

I still have not managed to connect the NMEA output of my old Furuno FCV668 sounder.
I tried all possible combinations, I do not receive anything ...

I checked, in case, the connectivity of Nmea4wifi which is efficient. It is not a hardware problem.

The NMEA data coming out of the sounder, according to Furuno's documentation, are of this type:
(nmea output of the sounder)
1 = td-h
2 = td-c
3 = rd-h
4 = rd-c
td in nmea = transmit data
c = cold / common / -
h = hot / high / +


With a RS232 USB/serial cable, when I connect the sonar TD+ on the RX of the serial/usb and RD+ sonar on the ground of the serial/usb, the data are received by OpenCPN.

However, I found that the $DDBT sentence sent by the sounder is not accurate, the checksum is missing.
The sentence sent is of this style, for example: $SDDBT, 0025.6, f, 0007.8, M, 004.3, F
whereas it should be of this form (with the checksum): $SDDBT, 7.8, f, 2.4, M, 1.3, F * 0D ...

Hence my question: does the Nmea4wifi filter input nmea sentences and reject sentences whose checksum is inaccurate or missing ??? (for example, if there is no asterisk * ?).

Best Regards,
Alain

Luis Sa
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Re: FURUNO FCV668 sounder

Post by Luis Sa » Sun Oct 20, 2019 6:54 pm

Hello Alain,

I just read again a previous topic about the Foruno sounder that you posted here. I also read the Foruno manual. Since you receive depth data on OpenCPN I see no reason why the multiplexer green led L? will not blink when you connect TXD-H to A? and TXD-C to B?. It would extremely useful to check the waveforms that the Foruno generates but than you would need an oscilloscope (by the way, I keep a cheap oscilloscope aboard my boat. It is very useful. It cost less than 20 euros). At least you could measure the voltage from TXD-H to TXD-C with a multimeter. It should be positive and almost zero when the sounder is not transmitting data (I am not sure how you could place the sounder without transmitting such data). Because you will be getting zeros and ones the multimeter will just show the, positive, average. Can you confirm that that voltage is at least positive?

I have some more ideas about what you could measure but I need to know if you are able to measure voltages on particular pins of the multiplexer. Can you? Also tell me which input port of the multiplexer are you trying to deliver the Foruno data.

Regarding the Nmea sentences and Check Some - No filtering. The multiplexer is constantly reading incoming characters. If no $ or ! arrives it ignores every thing. When it founds a $ or a ! then it keeps all next following characters until a <CR> is detected. The set of characters between the stating $ (or !) and the ending <CR> (and a <LF>) is the nmea sentence. The checksum comes before the <CR>. No check is made.

Regards, Luis

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Re: FURUNO FCV668 sounder

Post by schnapsy » Mon Oct 21, 2019 12:43 pm

Hello Luis,

Thank you for this very quick answer.
The input port of the multiplexer where i am trying to deliver the Foruno data are A3 and B3 (they work, I tested them with another nmea input).

I will try to go on the boat this week and at first, I will measure with a multimeter the voltage coming out of the Furuno and I will confirm if this voltage is positive.

If around me, I can not find an oscilloscope, I will order one on Amazon, it will always be useful thereafter.
As soon as I have an oscilloscope, I will send you the result of the measurements.

Best regards,
Alain

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Re: FURUNO FCV668 sounder

Post by Luis Sa » Mon Oct 21, 2019 2:04 pm

Hello,

The one I have in the boat is this one:

[20,74€ 24% OFF]Original JYETech Assembled DSO-SHELL DSO150 Digital Oscilloscope Module 9V Arduino Compatible SCM & DIY Kits from Electronics on banggood.com
https://banggood.app.link/LmIYVoe5X0

Regards Luis

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Re: FURUNO FCV668 sounder

Post by schnapsy » Tue Oct 22, 2019 7:08 am

Hello Luis,

So I ordered this oscilloscope.
As soon as it is delivered, I will send you a private message to determine the tests to be performed.
Regards,
Alain

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Re: FURUNO FCV668 sounder

Post by schnapsy » Wed Dec 04, 2019 9:31 am

Hello Luis,

I confirm that measurement with the multimeter gives positive results.
The voltage is positive (TXD-H, TXD-C).

I meanwhile went on the boat and with the oscilloscope (the same as yours), I made measurements.

I posted two short films about these measurements on this page.

https://www.schnaps.fr/articles.php?lng=fr&pg=873

If it helps ...

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Re: FURUNO FCV668 sounder

Post by Luis Sa » Thu Dec 05, 2019 1:33 am

Hello Alain,

In addition to a private message that I sent you this morning regarding the videos, I had another look at them, now in my PC, not on my smartphone and I notice a crocodile on the top of the video. I assume that the probe is similar to the one I have in my boat (now in Greece)

osc-probe.jpg
osc-probe.jpg (10.77 KiB) Viewed 20193 times

Now they sell the same oscilloscope with a better probe. In any case the black crocodile is what I call "aux input" in this post that I just made. So you should connect the red crocodile ("live input") to TX+ of your Foruno and the black crocodile to the Foruno ground. Then, in a second measurement you connect the red crocodile to TX- and keep the black crocodile connected to ground. I read again the Foruno manual and it has 4 wires for Nmea 0183. 2 for input and 2 for output. The output ones are TXD-H (white?) and TXD-C (black?). I am not sure if the TXD-C (black?) is the "B or minus side of a differential" output or if it is a ground! Check the connectivity between TXD-C (black?) and the metallic chassis of your unit with a multimeter.

You said in the forum that you were able to get the data on a PC using a serial to USB cable. If you remember how you connect it, tell me, and I should be able to deduct how to connect to the multiplexer. As the multiplexer input has an optocoupler you can connect TXD-H (white?) to An and TXD-C (black?) to Bn or vice versa. As your oscilloscope is powered up from a small 9V battery (is it? like mine) you can connect even connect the red crocodile to TXD-H (white?) and the black crocodile to TXD-C (black?).

Regards (and good luck!) Luis

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Re: FURUNO FCV668 sounder

Post by schnapsy » Fri Jan 24, 2020 10:39 am

Hello Luis,

After testing all the possibilities of connections, even adding an additional mass to check, nothing worked until ...

... until updating the software with the latest version (NMEA4WIFIV34.BIN) and there, without doing anything, with just the two wires connected, I finally get the display of the depth by Wifi ...

A problem solved ... :D
Thanks

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Re: FURUNO FCV668 sounder

Post by Luis Sa » Fri Jan 24, 2020 2:11 pm

Hello,

Thank you for confirming that the timing adjustment on the reception of ports P3 and P4 was improved in version 3.4.

Regards, Luis

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