NMEA multiplex - output position to VHF

[petter5]

I have a Digitalyatch dualnav GPS outputting at 115200 baud to a serial server rs422 to rj45 tcp/ip server. Connection in in opencpn is TCP 10.8.1.10 port 50000 - and this works fine.

I'm trying to use NMEA connection output to a Sailor 6222 DSC class A vhf to feed the VHF with position date for the DSC function. The VHF is 4800 baud.

According to the VHF's manual, General DSC specifications is:
GLL RMC ZDA GGA VTG GNS

I want to feed the output over TCP to the serial server 10.8.1.10:50001
The serial server is capable of 115200 baud, but can also be configuered for 4800 bad as required by the VHF. My question is: The GPS giving position to opencpn is configured at 115200 baud, but the VHF is only 4800 baud. Is there any way I can filter nmea sentences sent out so that I can successfully give required position data to the VHF at 4800 baud from the 115200 baud input to the system ??

[Brasshopper]

Baud refers to the speed of the connection. As I understand your system, the serial server connects particular ports on the IP side to particular serial connections. You sound like you are trying to loop openCPN output back through the serial server to the vhf. As long as you don't overrun the buffering of the serial server I don't see a problem. Baud is a physical link thing. Once you are done with that physical link, it is on to the next.

The only problem you might have is that fast physical links, like 115k bps/baud or Ethernet can send packets so fast that they can stack up in the device that is converting them to 4800 Baud. But since you are relaying the data from a GPS, probably that will not be an issue.

[petter5]

Originally Posted by Brasshopper

Baud refers to the speed of the connection. As I understand your system, the serial server connects particular ports on the IP side to particular serial connections. You sound like you are trying to loop openCPN output back through the serial server to the vhf. As long as you don't overrun the buffering of the serial server I don't see a problem. Baud is a physical link thing. Once you are done with that physical link, it is on to the next.

The only problem you might have is that fast physical links, like 115k bps/baud or Ethernet can send packets so fast that they can stack up in the device that is converting them to 4800 Baud. But since you are relaying the data from a GPS, probably that will not be an issue.

I ended up output only the minimal RMC sentence to avoid packets to stack up from the 115200 baud input. The VHF now displays GPS position correctly connected to the VHF 4800 baud input.