Erratic Seatalk1 conversion

Discussion and support for the Nmea4Wifi multiplexer - a 4-input Nmea 0183 wifi multiplexer.
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Joined: Tue Oct 19, 2021 3:43 pm

Erratic Seatalk1 conversion

Post by Arnaud » Wed Oct 20, 2021 7:23 am


Just installed a brand new NMEA4Wifi device las week-end in my boat.

I see erratic Seatlak1 to NMEA conversion, for example on depth.
Sometime the value is correct, sometime it is not.
Same for water temperature.
It's constantly switching between 3 or more different value, like 2.1, 1740, etc... 2.1 being the correct one (was in the harbour).

Attached is my wiring.
NMEA/Seatlak wiring schematics
(28.36 KiB) Downloaded 47 times
I first tested with ONLY Seatlak (Port4) connected and had already the issue, thus this not linked to the complexity of wiring.

On the wifi side, I have a PC with Lubuntu (Linux) and OPENCPN on UDP port 2000 and dashboard plugin showing depth.

Firmware version is 4.4.
I have seen multiple fixes in other threads regarding Seatlak and version 2.5,2.6,2.7, etc...
Could it be a bad merge/fix/bug still in 4.4 ?
(I used to be a software developper earlier in my carrier, if I can have source code, I may help)

Luis Sa
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Joined: Thu May 04, 2017 4:12 am

Re: Erratic Seatalk1 conversion

Post by Luis Sa » Wed Oct 20, 2021 8:33 am


Could you please send to my private email a photo of the PCB so that I can be sure what hardware you have. Since I started to offer both the TH and SMD versions earlier this year I changed the optocouplers that now are much faster. The new firmware (as 44) identifies the hardware it is running and use different timing to handle interrupts ( which are the base for SeaTalk input). As you are a programmer we can exchange information by email that will not confuse other users that read this forum. In the end we can write here a summary of our findings.

Regards, Luis

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