Upnorth
Member
I have an Evermore SA320 with the RS232 NMEA port. The RS232 has both an data send and a data receive connection. Anyone know why you would ever need to connect the data receive wire?
Evermore GPS receiver serial port
- Thread starter Upnorth
- Start date
elton
Well-known member
To upload waypoints.
Upnorth
Member
Why would the GPS receiver want to know waypoints - surely these go to the autopilot.
elton
Well-known member
You're correct of course. Perhaps it's to allow firmware updates, or factory test.
tillergirl
Well-known member
I think - but may be wrong - that it is essential as the receiving unit tells the sending unit when it is ready to receive. When I connected up my Evermore to my laptop it needed both connecting - and worked fine. And you can see that the data comes through in batches as though a batch gets sent, the sending unit then waits for an acknowledgement before it sends the next data batch. This could all be nonsense though. It just looks like its working like that.
When I connected the Evermore to my Furuno GP31, it failed. Quite why I don't know. I suspect that the firmware in the Furuno needs an update but I can't get an answer from Furuno at present.
When I connected the Evermore to my Furuno GP31, it failed. Quite why I don't know. I suspect that the firmware in the Furuno needs an update but I can't get an answer from Furuno at present.
Billjratt
Active member
MNEA talkers just talk and listeners just listen. The talkers don't wait for an Ack, Wack or Nack as in simplex comms. That is why you can only have one talker per group, but as many listeners as the driver will take. Multiple talkers on the same group will cause data collisions, as they aren't polite enough not to interrupt each other! As mentioned, you can have multiple listeners, which would mean multiple talkers if they all tried to acknowledge receipt of data.
It is reasonable for the GPS to know the waypoint so it can calculate course error and ETA etc. It is equally reasonable that you could save/generate your waypoints and routes on a laptop and then transfer them to the GPS.
It is reasonable for the GPS to know the waypoint so it can calculate course error and ETA etc. It is equally reasonable that you could save/generate your waypoints and routes on a laptop and then transfer them to the GPS.
Upnorth
Member
This evermore product is not a gps plotter, it's just the mushroom thing that looks at the satellites and outputs the lat/log data.
Bobobolinsky
New member
They are an excellent unit for the price though
Amulet
Active member
So that you can daisy-chain NMEA devices. It will presumably pass through NMEA sentences that have nothing to do with it. My understanding was that NMEA devices were supposed to do that. If the GPS is the last or only device in a chain it doesn't matter a monkey's that it's got an unused input. Maybe someone more expert will correct me, but I'd have thought the standard required it.
Norman_E
Well-known member
Seconded. My VDO chartplotter was connected to an old VDO GPS unit that only had 6 channels, and it kept losing fix. I replaced it with the bare wire Evermore unit which has 12 channels and have had no problems at all. It was about half the price of other makes.
tillergirl
Well-known member
Anyone know why I can't get my Furuno GP31 to 'find' it. It works fine feeding the plotter programme in the laptop but the Furuno ignores it.
Norman_E
Well-known member
You need to have both operating at the same speed. In NMEA 0183 mode it outputs the signal at 4800 baud, and the Furano unit must be set to receive at the same rate. On my VDO plotter there was a menu that allowed me to set the baud rate, and you need to look for that on the Furano.
tillergirl
Well-known member
Thanks. I don't appear to have any menu item on the Furuno to set the Baud. It appears it is already at 4800 since the manual says that when connected to any PC, the PC must be set to receive at 4800. I can select either Ver 1.5 or 2.0 of NMEA and that appears to be it.
wooslehunter
Active member
Seems as though for the normal user there is no reason to send data to the 320. According to the manufacture's website, it outputs the following NMEA sentences: GGA, GLL, GSA, GSV, RMC, and VTG. None of these are related to waypoint navigation. So, the device does not seem to be capable of driving an auto-pilot or knowing about waypoints.
Generally, a GPS that knows about waypoints will be able to drive an auto-pilot. Auto-pilots do not know about waypoints. The GPS does all of the navigation & tells the auto-pilot what to do. This is generally done with a NMEA APB sentence. This contains:
A Loran-C blink/SNR warning, general warning
A Loran-C cycle warning
0.10 cross-track error distance
R steer Right to correct (or L for Left)
N cross-track error units - nautical miles (K for kilometers)
V arrival alarm - circle
V arrival alarm - perpendicular
011,M magnetic bearing, origin to destination
DEST destination waypoint ID
011,M magnetic bearing, present position to destination
011,M magnetic heading to steer (bearings could True as 033,T
So essentially, the auto-pilot will know about bearings & steering. They will not know about positions.
Generally, a GPS that knows about waypoints will be able to drive an auto-pilot. Auto-pilots do not know about waypoints. The GPS does all of the navigation & tells the auto-pilot what to do. This is generally done with a NMEA APB sentence. This contains:
A Loran-C blink/SNR warning, general warning
A Loran-C cycle warning
0.10 cross-track error distance
R steer Right to correct (or L for Left)
N cross-track error units - nautical miles (K for kilometers)
V arrival alarm - circle
V arrival alarm - perpendicular
011,M magnetic bearing, origin to destination
DEST destination waypoint ID
011,M magnetic bearing, present position to destination
011,M magnetic heading to steer (bearings could True as 033,T
So essentially, the auto-pilot will know about bearings & steering. They will not know about positions.