Serial input

Discussion and support for the Nmea2Wifi multiplexer - a 2-input Nmea 0183 wifi multiplexer.
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jbonde
Posts: 12
Joined: Sat May 30, 2020 3:51 am

Serial input

Post by jbonde » Mon Jun 15, 2020 7:26 am

Is there a way to use the P3 input port on NMEA2WIFI as standard serial input instead of the current differential format used for NMEA 0183? Reason for asking is that I have a few Raspberries on board used for picking up data from GPS and temperature and pressure sensors etc. All this information can be provided as NMEA-serial strings directly to NMEA2WIFI so it can be transmitted together with the ST1 data I am planning to feed on P2.
The alternative, which I have tested, is to broadcast the RPi data as UDP as well. This is working fine along with the NMEA2WIFI test program but I would like also to have the option of hard wiring the units together if necessary.

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

Re: Serial input

Post by Luis Sa » Mon Jun 15, 2020 8:40 am

Hello,

P3 is an ouput port. May be you mean P1. If you mean P1 the answer is yes. The opto isolated inputs can be feed by RS232 signals.

Regards, Luis

jbonde
Posts: 12
Joined: Sat May 30, 2020 3:51 am

Re: Serial input

Post by jbonde » Mon Jun 15, 2020 11:25 am

OK, thanks. I was referring to the schematic at https://www.vela-navega.com/images/stor ... matics.gif where P2 and P3 are inputs connected to optocouplers and P1 is for power supply. Please let me know if you have another schematic I should look at instead.

jbonde
Posts: 12
Joined: Sat May 30, 2020 3:51 am

Re: Serial input

Post by jbonde » Mon Jun 15, 2020 11:35 am

RS232 compatibility is fine but this requires a -3/15V to +3/15V logic. I am looking for a serial input which recognizes a 0-5V logic (or better 0-3,3V). Is this possible to achieve or should I add a voltage converter like the MAX3232?

Luis Sa
Site Admin
Posts: 535
Joined: Thu May 04, 2017 4:12 am

Re: Serial input

Post by Luis Sa » Mon Jun 15, 2020 11:22 pm

Hello,

I am sorry about my misunderstanding regarding P3. There are schematics for the ´later units. Just small differences. You can get them here:

https://www.vela-navega.com/forum/viewt ... f=14&t=128

Regarding the RS232 problem I am not familiar with the RPi. May be it outputs serial TTL instead of RS232. There some tricks but normally an inversion is needed. My post here:

https://www.vela-navega.com/forum/viewt ... f=14&t=132

can be useful.

Regards, Luis

jbonde
Posts: 12
Joined: Sat May 30, 2020 3:51 am

Re: Serial input

Post by jbonde » Tue Jun 16, 2020 12:20 pm

Thanks for the update. A few suggestions if I may:

The schematic on the product page https://www.vela-navega.com/index.php/nmea2wifi should be updated if it doesn't provide the newest version.
In the "new" schematic resistors R3-R6 are changed to 330 ohm and the parts I received for my NMEA2WIFI is in line with the "old" schematic (R5+R6 are 470 ohm).
As for the P1-P3 confusion I suggest to use same reference for ports in the schematic as on the board/admin page.

With regards to the input the RPi outputs serial TTL 0-3,3V. I have tested and reversed the feed without success and checked if I could find a hint in your fine summary about serial communication. So any good suggestions would be appreciated.

best regards, Jesper

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