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Optoisolated DB9 RS232 ??
I'm trying to hook up a optoisolated DB9 cable/connector that I purchased
from Nautical Tech. (The Cap'n).. I'm confused.. They are using two different gounds. One is suppose to be NMEA "B"(signal ground) to GPS signal ground. The other is called Capn Transmit signal ground to AP input ground (and/or GPS/Radar ground) The NMEA B is going through the opto-isolator so I can't tell what DB9 pin it uses.. The Transmit signal ground bypasses the opto-isolator circuit and is pin 5 of the DB9. Here is the complete cable designation info: Yellow wire-- NMEA "A" (recieve Data)-- connect to GPS output wire Green wire-- NMEA "B" (signal Ground)-- connect to GPS signal ground wire Red wire-- Capn Transmit Data-- connect to Autopilot input wire (and/or GPS/Radar input) BlackBrown-- Capn Transmit Signal Ground-- connect to AP input ground (and/or GPS/Radar ground) So far I have ignored the Capn Transmit Signal wire and it isn't hooked to anything. My GPS is recognized and working fine with the software.. However, eventually I want the navigation software will need to send XTE to the autopilot.. I always assumed that XTE would be sent via the NMEA sentence. I can't figure out what to do with the extra ground wire. I can't get tech support from Nautical Tech. since I haven't been upgrading my softwere since ver 6.3. etc.. Comments. Steve s/v Good Intentions |
#2
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Optoisolated DB9 RS232 ??
"Steve" wrote in message
... I'm trying to hook up a optoisolated DB9 cable/connector that I purchased from Nautical Tech. (The Cap'n).. I'm confused.. They are using two different gounds. One is suppose to be NMEA "B"(signal ground) to GPS signal ground. The other is called Capn Transmit signal ground to AP input ground (and/or GPS/Radar ground) The NMEA B is going through the opto-isolator so I can't tell what DB9 pin it uses.. The Transmit signal ground bypasses the opto-isolator circuit and is pin 5 of the DB9. Here is the complete cable designation info: Yellow wire-- NMEA "A" (recieve Data)-- connect to GPS output wire Green wire-- NMEA "B" (signal Ground)-- connect to GPS signal ground wire Red wire-- Capn Transmit Data-- connect to Autopilot input wire (and/or GPS/Radar input) BlackBrown-- Capn Transmit Signal Ground-- connect to AP input ground (and/or GPS/Radar ground) So far I have ignored the Capn Transmit Signal wire and it isn't hooked to anything. My GPS is recognized and working fine with the software.. However, eventually I want the navigation software will need to send XTE to the autopilot.. I always assumed that XTE would be sent via the NMEA sentence. I can't figure out what to do with the extra ground wire. I can't get tech support from Nautical Tech. since I haven't been upgrading my softwere since ver 6.3. etc.. Comments. Steve s/v Good Intentions Surely Ground is Ground, and if there are 3, or even 10 ground wires, they all go to the same pin? -- Remove "nospam" from return address. |
#3
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Optoisolated DB9 RS232 ??
Hi Steve,
The NMEA A and NMEA B wires are completely isolated from the rest of the circuit. NMEA B is not a ground wire but you do hook it up to the ground of the GPS. The ground wire to the autopilot is the same ground as from the computer. The isolator only isolates the input to the computer. Here is the complete cable designation info: Yellow wire-- NMEA "A" (recieve Data)-- connect to GPS output wire Green wire-- NMEA "B" (signal Ground)-- connect to GPS signal ground wire This is correct info, although the NMEA "B" is not a ground, it is 'floating', aka isolated from anything, only connected to the circuitry inside the isolator, just like NMEA "A" Red wire-- Capn Transmit Data-- connect to Autopilot input wire (and/or GPS/Radar input) BlackBrown-- Capn Transmit Signal Ground-- connect to AP input ground (and/or GPS/Radar ground) This is also correct. So far I have ignored the Capn Transmit Signal wire and it isn't hooked to anything. My GPS is recognized and working fine with the software.. However, eventually I want the navigation software will need to send XTE to the autopilot.. I always assumed that XTE would be sent via the NMEA sentence. I can't figure out what to do with the extra ground wire. Well you have to connect it to the ground of the autopilot. This is can all be pretty confusing, it has to do with so called "single ended" interfaces and "differential" interfaces. I have written a web page about this, which describes all sorts of connections between these two types of interfaces. You can find it at http://www.shipmodul.com/en/connections.html In your case, the connection from GPS to the isolator compares to figure 4 and the connection from the isolator to the autopilot compares to figure 2. The isolator only isolates the input (GPS) from the computer, not the output that goes to the autopilot. Regards, Meindert |
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