Vela Navega Forum

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.

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

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.

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?

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

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