Trimble - trimble comms

[e3120]

For messy reasons, I want to feed gps info from my 750 to 500. I've butchered an old serial mouse cable and shoved it into the back of both units. Difficulty is what comms protocol to use. The only one I can get to work is tsip, but when use this, the 500 switches the 750 from rangepoint to egnos, rp being before the 500's time.

I thought that the slave in these arrangements didn't care how the position info was determined but it's trying to be smart. Tried nmea output on 750, ext corrections on 500, but no joy. Some screenshots:

750 output

500 input

Which when you select ext tsip you get

This is what controls the GPS source on the 750.

Any ideas? I could just use the egnos signal, but it significantly limits what I'm trying to achieve.

 

[Pheasant Surprise]

Trimble proprietary protocols are finicky. TSIP is way more than just a positioning/timing output protocol too, it’s like Topcon GRIL in that it’s a protocol that allows the receiver to be configured with special commands so the 500 could be sending config type commands back to the 750.

Have you got both receivers running the latest firmware?

My shot in the dark: it could be a position output ‘precision’ thing. That is the 750 is sending position output with a higher number of decimal places on RP than the 500 can cope with. That’s just a theory though, I’ve got no basis that’s your exact issue.

Simple NMEA should work, as long as your selected / expected message sentences are correct and the refresh rate matches up.

Sorry I don’t have any Trimble tractor screens/receivers here to play with replicate to check only Trimble fixed base receivers.

 

[e3120]

Cheers. It deffo seems the 500 is sending config instructions back, as it's exactly when i configure the 500 (or plug in pre-configured) that the 750 swaps to egnos.

I realise trimble stuffs not your bag, but what setting would you suppose to use on the 500 when sending nmea across? There's no nmea input option, just ext tsip & ext corrections. Tried that, I think.

Are these the things that should match? (data parity now both set to odd, to no avail)

 

[Pheasant Surprise]

That’s just your basic port settings. I’d usually leave both ends set to the same speed / baud rate (the highest common one) and leave parity as ‘none’ and 1 stop bit.

Now you should have an NMEA output setup on the 750 such that you can configure the refresh rate (usually 5 or 10 Hz) and the NMEA “sentences” (message types) that you need to send to the 500 for position and speed. Typically these are GGA, VTG and GSA at a minimum. But I’ve not checked specifically to see what the 500 needs.

 

[Pheasant Surprise]

By the way... not being familiar with the 500’s, are you sure it can accept an NMEA input for position/heading/speed?

Can you put up your input config screen from the 500?

 

[e3120]

I've got the 2nd picture in the first post. Have found that ext corrections is rtcm - is this for rtk? It would seem that it and tsip might be the lot. Have just found more options in advanced port settings (Inc nmea input) but still not sure what to set correction source to. If weather is fresher tomorrow, hopefully thought is clearer.

Thanks again.

 

[Pheasant Surprise]

Yeah RTCM is for RTK correction input. You need position, heading and speed via NMEA.

 

[Pheasant Surprise]

I've got the 2nd picture in the first post.

I just clocked that - but if you look closely (I didn’t admittedly the first time) that’s the correction source.

That presumes you’re using the external antenna on the 500 for your basic position, and not from an external receiver.

 

[e3120]

I know, but can't find anything else. It comes from the GPS source menu. Selecting tsip in there definitely gives position etc without any antenna connected.

 

[Pheasant Surprise]

Looks like it will only do NMEA output on the 500. So you have to work with TSIP to get position etc on input.

If that’s the case, the best the 500 will do is EGNOS over a TSIP connected position input. Or so it would appear...and it’s pushing the 750 to give it. Need a Trimble person to confirm if there’s any better way of doing it or whether that’s your limit now.

All the Trimble boys and girls only work M-F it seems

 

[Badshot]

I needed to get a GPS output from my 750 to go to my drill.
I wasted a day or two trying.
Eventually found out I had to take the output from the autopilot diagnostics port not direct from the back of the 750.

 

[e3120]

I needed to get a GPS output from my 750 to go to my drill.
I wasted a day or two trying.
Eventually found out I had to take the output from the autopilot diagnostics port not direct from the back of the 750.

I had heard of that, but only on ez pilot here.

Looks like it will only do NMEA output on the 500. So you have to work with TSIP to get position etc on input.

If that’s the case, the best the 500 will do is EGNOS over a TSIP connected position input. Or so it would appear...and it’s pushing the 750 to give it. Need a Trimble person to confirm if there’s any better way of doing it or whether that’s your limit now.

All the Trimble boys and girls only work M-F it seems

I was becoming resigned to egnos but remembered this thread, where even if the core idea didn't work, they are pretty certain a 500 should be able to receive a higher accuracy position over tsip, they had a 252 in mind.
https://talk.newagtalk.com/forums/thread-view.asp?tid=62344&DisplayType=flat&setCookie=1

Anyway, fresh day, fresh ideas and I have it working with a dirty solution. If I connect them using tsip, let the 500 switch the 750 back to egnos and then pull out the Rx wire from the 750 (connects to Tx on 500), I can then change to rangepoint. The 500 appears to be working OK, reporting ~ 13 sats and tracking position around the yard. Not ideal, as if either is powered down (Inc by starter motor), I'm back to square one. Next step is to put a switch on that wire, make the cable a bit more robust and do some more testing. I guess the 500 is constantly shouting down the wire "change to egnos" and might get the huff after being ignored.

If it works, then it'll do me. Sometimes I have to ignore my character and accept the 90% solution.

Incidentally, this thought process was inspired by your galileo thread. If the accuracy doesn't get watered down by the big boys, I imagined there might be a case for feeding non-galileo receivers (like the 750) from a simple galileo receiver, funded by kicking rangepoint subs into touch.

 

[towbar]

Wouldn’t be hard to stick a little processor like arduino between the 2 to intercept the 500 transmit and block only the data you want. If your not into that level of programming drop pm might be able help as would be keen to send corrected data to a 500 myself

 

[Pheasant Surprise]

If I connect them using tsip, let the 500 switch the 750 back to egnos and then pull out the Rx wire from the 750 (connects to Tx on 500), I can then change to rangepoint. The 500 appears to be working OK, reporting ~ 13 sats and tracking position around the yard. Not ideal, as if either is powered down (Inc by starter motor), I'm back to square one. Next step is to put a switch on that wire, make the cable a bit more robust and do some more testing. I guess the 500 is constantly shouting down the wire "change to egnos" and might get the huff after being ignored.

Can you not simply get the position info out, using the TSIP setting on both units, with just the Tx wire (and comms ground) on the 750 going to the Rx pin on the 500 (ie simplex comms from 750 to 500 only)?

(This is generally how most RTK radios are wired to receivers - you really only need the transmit path from the radio to receiver to get correction, the return path is redundant)

Or do you need the Tx wire from the 500 going to Rx on 750 (ie full duplex comms) to setup the initial handshake etc?

 

[e3120]

It needs to handshake, I suppose because it's a more interactive connection.

 

[e3120]

Wouldn’t be hard to stick a little processor like arduino between the 2 to intercept the 500 transmit and block only the data you want. If your not into that level of programming drop pm might be able help as would be keen to send corrected data to a 500 myself

My programming is limit to a bit of picaxe, but no serial stuff, I'll be in touch. Could well be useful for future exploits.

 

[Pheasant Surprise]

Wouldn’t be hard to stick a little processor like arduino between the 2 to intercept the 500 transmit and block only the data you want. If your not into that level of programming drop pm might be able help as would be keen to send corrected data to a 500 myself

My programming is limit to a bit of picaxe, but no serial stuff, I'll be in touch. Could well be useful for future exploits.

Some bloke has put an NMEA to TSIP converter on Github. Might be worth a look in case you do ever decide to go down the TSIP filter/translating direction.

https://github.com/Kelvin312/NMEA-to-TSIP-Converter

 

[Pheasant Surprise]

Some interesting TSIP / NMEA developer stuff here too still tucked away on Trimble's website.

1. TSIP and NMEA Application Developer’s Guide
2. Trimble GPS Studio Application
3. User Guide - Trimble GPS Studio

Fairly old, but actually all similar-ish vintage to the 500's etc. So could for example be useful for port configuration using Trimble GPS Studio loaded on a laptop hooked up to the receiver. Similarly the app development guide if you wanted to roll your own solution...

 

[e3120]

Well, used in earnest burning off a bit of grass this morning. A bit of cab clutter but relaxed operator.

500 controlling ez-boom; 750 driving the ez-pilot, both from single rangepoint receiver.

 

[Badshot]

I suppose the 500 can't do the pilot, only ez steer?