Robnet Network Specifications

[R_C]

Does anyone have a source for technical specifications for the older Robertson (now Simrad) Robnet network? Is it a proprietary protocol or is it NMEA 0183? Any specs on the pinout or signals for the Robnet cables? I'm troubleshooting my old Robertson AP300 autopilot and would like to know what data is on the cables. Thanks.

[gbkersey]

Originally Posted by R_C

Does anyone have a source for technical specifications for the older Robertson (now Simrad) Robnet network? Is it a proprietary protocol or is it NMEA 0183? Any specs on the pinout or signals for the Robnet cables? I'm troubleshooting my old Robertson AP300 autopilot and would like to know what data is on the cables. Thanks.

Looks like most of this is in the manual...
I see an NMEA table at the back and pin outs for many of the inter unit connectors there....

The manual is here...

[R_C]

Originally Posted by gbkersey

Looks like most of this is in the manual...
I see an NMEA table at the back and pin outs for many of the inter unit connectors there....

The manual is here...

Thanks. I found the Robnet cable pinouts in the manual. The AP300/AP300X does have one NMEA0183 input and one output port but the data on the Robnet cables is apparently not NMEA. I have been told by someone much more knowledgeable on Robertson autopilots than me that Robnet is much, much faster than NMEA0183 and bidirectional, similar to CanBus. Unfortunately, Simrad/Robertson told me they could find no documentation on the Robnet bus in their archives. It would be nice to find some documentation.

[tayana55]

Originally Posted by R_C

Thanks. I found the Robnet cable pinouts in the manual. The AP300/AP300X does have one NMEA0183 input and one output port but the data on the Robnet cables is apparently not NMEA. I have been told by someone much more knowledgeable on Robertson autopilots than me that Robnet is much, much faster than NMEA0183 and bidirectional, similar to CanBus. Unfortunately, Simrad/Robertson told me they could find no documentation on the Robnet bus in their archives. It would be nice to find some documentation.

Robnet is a multidrop RS485 network, it is in no way compatible at hardware or software level with NMEA.

What is it that you need to do with the protocol info ?

To read the info into a PC for example you would need a robnet to USB converter and proprietary software to decode the sentences.

[R_C]

Originally Posted by tayana55

Robnet is a multidrop RS485 network, it is in no way compatible at hardware or software level with NMEA.

What is it that you need to do with the protocol info ?

To read the info into a PC for example you would need a robnet to USB converter and proprietary software to decode the sentences.

Because parts are becoming increasingly difficult to find, even on eBay, I am exploring alternatives. If the protocol was well documented and available, it might be possible to create my own basic control head. I may also use the NMEA output data to create my own rudder angle display as a backup.

[tayana55]

Originally Posted by R_C

Because parts are becoming increasingly difficult to find, even on eBay, I am exploring alternatives. If the protocol was well documented and available, it might be possible to create my own basic control head. I may also use the NMEA output data to create my own rudder angle display as a backup.

I haven't seen any information on the protocol whatsoever, however I did scope out some of the signals because I am in a similar position to you.

I am not in the market to replace my complete system yet because the Simrad kit is fairly serviceable.

What I have found out is that the interface is RS485 signal level
The data is sent in packets on a multidrop network.

If you need a rudder angle display, NMEA is the way to go, look up the RSA sentence and decode that

[R_C]

Originally Posted by tayana55

I haven't seen any information on the protocol whatsoever, however I did scope out some of the signals because I am in a similar position to you.

I am not in the market to replace my complete system yet because the Simrad kit is fairly serviceable.

What I have found out is that the interface is RS485 signal level
The data is sent in packets on a multidrop network.

If you need a rudder angle display, NMEA is the way to go, look up the RSA sentence and decode that

I'm also not interested in replacing the complete system. I revived a control head after replacing leaking capacitors but the lack of replacement parts, even on eBay, got me thinking of alternatives for a backup. How do you create a Robnet to USB converter? Would it then be possible to sniff and reverse engineer the packets? I can write software, if necessary, to sniff the packets but is there an open source utility that might do the job to capture the packets for further analysis?

I just recently found the manufacturer of the circular connectors used with Robnet so I have been creating my own cables. I found enough parts on eBay that I am attempting to create a bench scale test system for my AP300 autopilot.

[tayana55]

Originally Posted by R_C

I'm also not interested in replacing the complete system. I revived a control head after replacing leaking capacitors but the lack of replacement parts, even on eBay, got me thinking of alternatives for a backup. How do you create a Robnet to USB converter? Would it then be possible to sniff and reverse engineer the packets? I can write software, if necessary, to sniff the packets but is there an open source utility that might do the job to capture the packets for further analysis?

I just recently found the manufacturer of the circular connectors used with Robnet so I have been creating my own cables. I found enough parts on eBay that I am attempting to create a bench scale test system for my AP300 autopilot.

If you have a J300, the board on the right is the processor board. Just above the robnet connector you will see a 75176 RS485 driver chip, if you check the data sheet and follow the receive line it goes to TP22, the transmit line is TP23 on the rhs of the board. This is at 5V TTL level.

Connect a TTL to USB converter to get the data into the PC.

[R_C]

Originally Posted by tayana55

If you have a J300, the board on the right is the processor board. Just above the robnet connector you will see a 75176 RS485 driver chip, if you check the data sheet and follow the receive line it goes to TP22, the transmit line is TP23 on the rhs of the board. This is at 5V TTL level.

Connect a TTL to USB converter to get the data into the PC.

Excellent. I found the DS75176BM chip on the J300 board and downloaded the datasheet from TI. I'll get a TTL to USB converter and start exploring. Then again, I already have an TTL to RS232 converter so I could probably use that with a USB serial adapter. Thanks.

[tayana55]

Originally Posted by R_C

Excellent. I found the DS75176BM chip on the J300 board and downloaded the datasheet from TI. I'll get a TTL to USB converter and start exploring. Then again, I already have an TTL to RS232 converter so I could probably use that with a USB serial adapter. Thanks.

If you remove the Eprom from the J300 and dump its contents via an Eprom programmer, you will find a lot of clues. Send me the bin file and I can help you

[R_C]

Originally Posted by tayana55

If you remove the Eprom from the J300 and dump its contents via an Eprom programmer, you will find a lot of clues. Send me the bin file and I can help you

That sounds like a lot of work for this hardware novice. A bigger priority is to see if I can come up with an alternate LCD solution. Both LCDs are shot on an AP300DL I bought cheaply on Ebay for parts. The small LCD, the same one on my working AP300 control unit, is 80 columsn by at least 28 rows and uses a PCF8578T driver and two PCF8579T 40-column drivers. The PCF8578T datasheet shows it uses an I2C interface and documents the I2C commands.

If I could confirm the I2C commands, it might be possible to tap into the I2C bus with a separate microcontroller and recreate the display on its own LCD.

[tayana55]

Originally Posted by R_C

That sounds like a lot of work for this hardware novice. A bigger priority is to see if I can come up with an alternate LCD solution. Both LCDs are shot on an AP300DL I bought cheaply on Ebay for parts. The small LCD, the same one on my working AP300 control unit, is 80 columsn by at least 28 rows and uses a PCF8578T driver and two PCF8579T 40-column drivers. The PCF8578T datasheet shows it uses an I2C interface and documents the I2C commands.

If I could confirm the I2C commands, it might be possible to tap into the I2C bus with a separate microcontroller and recreate the display on its own LCD.

Now that sounds like hard work to me
Can't you find replacement LCD dispalys, they will be standard graphic LCD 160x128 pixel

[R_C]

Originally Posted by tayana55

Now that sounds like hard work to me
Can't you find replacement LCD dispalys, they will be standard graphic LCD 160x128 pixel

I sure wish replacement LCDs were available but they don't appear to be standard. The small LCD is only 80x28 pixels.

[tayana55]

Originally Posted by R_C

I sure wish replacement LCDs were available but they don't appear to be standard. The small LCD is only 80x28 pixels.

According to the specs in the manual it is a 80x32, or do I have the wrong unit ?

Autopilot Display:
Type: ............................................... Backlit LCD matrix display
Resolution: .................................................. ............ 80 x 32 pixels
Graphic Display (AP300DLX only):
Type:............................................. .... Backlit LCD matrix display
Resolution:....................................... .....................160 x 128 pixels

[R_C]

Originally Posted by tayana55

According to the specs in the manual it is a 80x32, or do I have the wrong unit ?

I forgot about the manual and just counted the pixels. But you're right, the small LCD is 80x32, which confirms the two rows of 56 contact pads on the PCB (2 * 56 = 80 + 32) . Any replacement would have to be exactly 80x32 and match the approximately 1.25mm pitch of the contact pads. I haven't been able to find one. Most LCDs come mounted on their own PCB complete with driver/controller.