Talk to my PC ....

[Guest]

We all hear about NMEA / Seatalk etc. Protocols used to transfer info between instruments and PC etc.

Now my question is .... as Echo Sounders and Speed Logs use what would surely be simple language to communicate and convey the pulses etc. to the head for calculating speed / depth. Is it possible to feed that pulse direct to a PC to have it displayed WITHOUT having a display head ..... obviously a convertor etc. would be needed.

I ask because like many I have simple LCD displays without provision for repeaters etc. Therefore would think that splitting the signal between head and PC may work IF I can get a suitable box.

I know that Echo Sounders cable length is part of the equation of travel vs time to get the depth etc. This could be compensated surely in the PC box ??

Interesting little project for someone ??



<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[Oldhand]

It would need to be a very specialised box and one would need to know all the signal levels/frequencies and calibrations to be processed. The echo sounder would be tricky as you need the timing for the transmit pulse which may only be available in the instrument control head.

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[Guest]

Maybe thats why I posted ??.

Its not a nut and bolt job - so onto others with the brains !

But imagine - if someone did it - which I am sure it can be done ..... what a revolution.



<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[Anthony]

Question is why? then you are reliant upoin your PC for all of your info, and have a single point of failure, and lets face it PCs are power hungery and fragile on boats (but yes I love having mine on board for nav etc). However I also like having seperate insturments so that I can read the depth and speed without having to boot the PC up.

If you want to read all this data on your PC then just plug into the NMEA output of the instuments, there are windows progs around to display it all, or it would not be to hard to write a new one to do whatever you want, or display the info on remote character based LCDs.

I am also just building a character based LCD NMEA repeater (using a PIC chip), that I can program to pick up any info off the NMEA network and display it how I want, thats low power and again doesnt rely on a PC, but again uses teh head to drive and interpret the sensor, and pass out easy to use NMEA strings.

Anthony



<hr width=100% size=1>The difference between men and boys, is just the price of their toys...

 

[Guest]

With due respect - point missed ...

My instruments do not have nmea out or repeater possibility.

Second I did mention that splitting of signal so that head and PC display.

MY idea is that Seatalk etc. are proprietary and difficult to 100% interact with NMEA .... etc.

My idea is to bypass all this commercial limitation and have pulses / etc directl;y read.


<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[tome]

Re: With due respect - point missed ...

Using a PC for instruments doesn't seem one of your brightest ideas Nigel!

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[snowleopard]

what passes between the control head and the transducer is not a 'language'. the control head of an echo sounder transmits a pulse to the transducer which in turn picks up the echo and sends it back to the head. if you tap into this you will interfere with the signals. you might possibly replace the control head completely in which case you would need to generate the pulses and interpret the returns yourself. seems like a lot of hard work. far simpler to interpret the nmea output from the head.

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[Anthony]

Re: With due respect - point missed ...

Sorry Nigel, I missed the point totally! Apologies...

if they are still connected to the head then that will power the transducer for the depth, so really it would be a case of putting an osciloscope on them and seeing what waveform is produced for given speeds / depths. Once you know the peak to peak voltages of the waveform you could then use a suitable interface to get that signal into the PC where software could read it.

There are commercial analog PC interfaces, Pico is one that springs to mind. Most are primarily aimed at usign the PC as an oscilloscope, however I think they have some software development tools / libaries that would enable you read the signal with code and then write your own code to interpret it. These interfaces should also be quite high impredence so as not to effect your existing heads. However its not an easy task, and I would imagine, bespoke to each intrument and manufacturer. As more and more instruments now have NMEA out, I suspect it would be more cost effective to ebay the instruments you have, and try to pick up some bargains at the boat show or boat jumble. I say that purely from trying many projects to reinvent the wheel, and often ending up spending as much financially, and even more in time, than if I had just bitten the bullet in the first place. I am sure given enough time you could do it, but I dont predict it being that easy unless you are reasonable at both electronics and software development.

Anthony


<hr width=100% size=1>The difference between men and boys, is just the price of their toys...

 

[Guest]

Got me thinking ....

I know the sensible way is to replace all with a set that allows NMEA out .... but note that I also run the GPS Nav group and this would be an interesting addition to our and MY boats line-up.

I know the pulse and timing etc. etc. not technically - but the idea of why it works with the standard head ..... the thought of an oscilloscope .... mmmmmm ...

Now the pulse (e/s) is triggered by a signal from head to transducer - which changes the electrical pulse to a sound wave, this rebounds to the transducer which now converts it back to electrical pulse .....(please excuse me all those experts .....but I think I'm close enough to principle ......) So as I see it - we would have to generate the pulses at correct time intervals and correct strength etc. We would then have to receive the return lesser strength pulse.

OK maybe I give up ????


<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[Guest]

we all have off days !

Its been a question with me for a long time .... and today I'm bored ..... works quiet, someone stole my lab managers car, just received a large bill for sonmething I don't want- cause it dinno work ...

C'mon it has its points ?


<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[bedouin]

For the log it should be pretty straightforwards. That is just a pulsed waveform so counting the pulses in a known period of time is all you need. I should think that you can get an IC to do that for a few pence.

The depth sounder is probably a lot more complex. The dedicated head has the advantage of knowing when it is transmitting and when the transmission stops, whereas anything trying to piggy-back off the same signal needs to do additional processing to work out where the transmitted pulse starts/finishes and the reflected pulses begin. The you need a bit of processing to convert the analogue reflection into a depth.

If I were doing it I would probably try to use a PIC with a comparatively simple input circuit; but it might just be possible to put the signal through a low pass filter and feed it into an audio ADC in the PC.

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[peterb]

If you remember using one of the old Seafarer sounders (with the neon display) you'll remember that the return signal is not necessarily a single clean pulse. There may be signals from fish; on a mud bottom the return may be quite fuzzy. You'll need to put in software (or hardware) to sort it out. I suspect that that will need A/D conversion first.

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[Jools_of_Top_Cat]

I would guess that you would be better to tap into the depth sounder head unit somewhere in the circuit just as it sends the data to the screen. Whether this is graphical or just plain digital data. The interface to the PC should then be easy and you will not be loading down the transducer circuit.

The dedicated head unit would have to be running. If you are looking for just numbers to be processed then I think (think) it is an probably a simple 8 bit word to the LCD, probably even ascii too.

<hr width=100% size=1>Julian

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