I never used the EVB Modules… What I could say from using the breakout boards is, that you have to connect TXD (output) from moving base to RXD2 (correction input) on rover. You then get $PSTI,032 message output with data like up-projection und angle between north and the two modules. You dont get RTK Postition at the moment, as you cant give the correction from your static base to the moving base! This is where we need the precisely moving base mode, which is still in development as they told in their forum 
At the moment AOG calculates an the roll from the up-projection and the distance between the antennas and also corrects the heading by 90 degree as the antennas have to be next to each other for the roll. I’m not quite sure, but I think the rover has to be on the left and the (precisely) moving base on the right, but you could easily try this out with a working setup. Of course you also have to set the right configuration in AOG for the source of heading and roll.
As I dont have time to go on with the project at the moment I hope the firmware update will be available when I need it… Sure I will keep you updated!
One thing about the breakout-boards I have to say here: There is only this little coax connector on the pcb wich is not really reliable. I have had some issues with it while building my base and gnss-stick. I wouldnt trust these inside the cab of a tractor. This is also one reason why I think about building a custom pcb with the PX1122R an a bigger connector on the pcb edge like on the evb module.
Thanks THiamu, I have the antennas front of cab and rear for heading only. I am plenty pleased with mma for roll. I didn’t realize we couldn’t connect for rtk yet. Might have been a little hasty on my purchase. For now I guess I’ll just use one module and bno55 as we are intersecting cotton rows and need rtk correction. Please post if they get they release the coding for the dual setup. Thanks again
A question @Jhmach : is there a specific reason that you chose a front/rear antenna setup + MMA ? If you went for a left/right setup, you could get rid of the MMA as well, if I’m correct
I believe you are correct, and I may be wrong in my thinking, as I am still very new to electronic side of this, but it’s my understanding if you were to lose connection to one of the antenna the offset to center would be off, where if I lose connection front and back I only lose heading. Please correct me if this is not so, because I would prefer having less components in the box.
I think this is not exact, but as no one had yet the opportunity to implement a moving baseline + rtk fix setup with SkyTraq hardware, what will follow is only assumptions.
I guess one of the two receivers in the cab will get the NTRIP stream and the other not. So if you lose fix on this receiver, the tractor position becomes inaccurate. If this receiver is also the moving base (like in a setup using two ZED-F9P), you keep the heading. On the other hand, if only the other receiver (the rover of the moving baseline system) loses rtk fix, heading becomes inaccurate but you should keep the absolute position of the tractor.
To properly address these issues and provide AOG with the most relevant data, it would probably be necessary to use an ESP32 or equivalent as an interface (like it is done with dual antenna setups with ZED-F9Ps and MTZ8302 program). Advantages would be at least the following :
- Reduced complexity in AOG to keep it compatible with as much receivers as possible
- Ability to generate a “virtual antenna” in the middle of the two physical antennas, with offsets if needed
Here, people discussed about physical implementation of a left/right moving baseline setup, and here about the (dis)advantages of a front/back setup.
I have to share some information about the PX1122R with you:
Some days ago they released a new firmware with an “advanced moving base mode”, see User-Guide page 28.
So I think what I was waiting for should be possible now. At the moment I only have two modules at home from wich one works inside my base on the roof of my house, so I cant test the setup at the moment… Maybe @Jhmach wants to try it out and give some feedback? If you take the NMEA output from Receiver C into AOG and put antenna C on the left (antenna B on the right) I would hope it already works with AOG.
As far as I read the User Guide I think the maximum update rate will be 5Hz. For the experts with a working setup: Is this enough? Do we need more than 5Hz?
I also asked some additional questions on the NavSpark-Forum about NMEA output, update-rate and pin-description.
If I find some time for that, I will design a pcb with two PX1122R the next days (weeks) and order all the parts for a first setup…
This is great THiamu. However I used my second antenna this last week for a permanent base on the barn. I will get another one coming and give this a try.
Also thanks for sending a simple hookup drawing, it take most of the frustration out of these new setups.
The only problem is, in the linked User-Guide you dont find the SDA and SCL pins… They should next to TXD on pins 6/7 as you find on the datasheet of the PX1122R I think…
On the hookup drawing they take the NMEA output from Receiver B… I think and hope there is also an NMEA output on Receiver C as AOG expects an $PSTI,032,… message in the NMEA stream with up-projection and baseline-length between the two antennas on tractor wich could only be taken from Receiver C and NOT from Receiver B (we dont need the baseline-length and up-projection between our static base at home and the rover on tractor)
My modules are marked. I ordered a couple ublox antennas today. Will give it a try soon as they come in.
I got an evaluation board (has the SCL & SCA pins marked) and a breakout board (pins not well marked). I have them working with NTRIP and together on a short baseline. I’ll have a go at flashing the new firmware and see what messages come from what. That diagram implies to me that receiver C gives information back to receiver B? Maybe the PSTI message from receiver B is modified. I have been turning off the SkyTraq messages (because I didn’t understand what they were for). Mine are still on the bench being tested and not on the tractor yet…
For a PCB I would be inclined to design it for the breakout board as a socketed component rather than as a smd chip as it would be a bit more serviceable in that you could remove the modules and and easier to solder given the chip is the most expensive component.
Yes I would totally agree with you, but I can report, that this small coax connector on the breakout-board is really fragile… I’ve had some issues with antenna connection on my base und gnss-stick setup with the breakout-boards. This is why I would prefer the evaluation board or the small smt receiver wich is also the cheapest. (99$ SMT; 125$ breakout; 150$ eval.)
About the message streams…
Yeah those antenna connectors are tiny. The sma connector is a lot better.
5Hz is a bit on the slow side from recommended isn’t it? I wonder if that’s a comms between receivers constraint or processing constraint?
I’ve discovered that our state’s CORS network has recently become a free service whereas it used to be subscription (eye wateringly expensive) only so I no longer need my own base. That leaves me with a spare receiver so dual gps would be a good use of it.
Got antennas today. Will try to get it connected for testing tomorrow. Stay tuned for questions, I lack a lot of understanding on the flow here.
I just set up in the pickup to test. Connected everything according to the navspark outline. I took my rfd900 antenna out of the tractor for rtk. I am not getting the rtk correction through the module. Works good on the ublox c099 board.
If you look at the pictures, without rtk, the vehicle always points north, however with several trips around my driveway on baseline, the vehicle is pretty close to center, and the antennas are left side and right. Have tried reversing them and front to back both ways.
I did update the firmware off of the website, and made the rover a moving base, and the master a kinetically moving base and normal. Also tried float.
I wonder, since it gets heading from the rtk base, it that is my problem, but I don’t read anything to help correct the lack of rtk connection. If anyone knows please respond.
Did you chose dual GPS as source for heading in AOG? I think its on sources tab in settings, but don’t have AOG here at the moment…
For the rtk position I think as far as I understand the answer in NavSpark forum we could get this from moving base receiver, but not from the rover behind moving base…
The heading as implemented by SkyTraq/NavSpark now is different from what I coded in AOG. The parsing of the NMEA stream in AOG looks for the baseline course in PSTI,032,… message. This is should be the direction to static base if using receiver B and the direction to moving base if using receiver C. After parsing the code turns the direction by 90 degree to get the actual vehicle heading. Similar with the roll: Parsing takes up-projection from PSTI, 032,… message which should again be different if using receiver B or C output… The heading as defined by SkyTraq is in some different NMEA message which isn’t read by AOG at the moment but should be the same on receivers B and C.
I hope you understand what tried to say… English is not my mother tongue 
It would be really nice, @Jhmach if you would post some lines of the NMEA output of moving base B and rover C receivers if you don’t mind to give your coordinates to us.
I do have dual antenna selected in aog. As I understand it, the skytac should receive rtk through rx2, and show rtk radio in gnss viewer. However gnss viewer show 0 in rtk radio. I feel certain about my signal from base to rover radio, but it seems the skytraq in not set to receive it. I wonder if you or someone else has a single skytraq rover successfully receiving rtk through a radio, as I am still new to rtk.
Wasn’t sure what all you needed so I just snapped a few shots
OK, something in your setup doesnt work, hard to find out what is wrong with it from here…
Yes, I have a working setup with base and single rover. Base (also the PX1122R) on the roof of my house broadcasting rtcm3 to the internet and rover connected via a bluetooth-serial adapter to my android phone with lefebure ntrip client or over usb to AOG (with integrated ntrip client). Working pretty good and giving rtk position after some seconds.
As far as I could see from your pictures there is no connection to base station or moving base (or at least no calculation of correction) and therefore no heading or anything. Also there is a lot of change in satellite signal as they are changing from one picture to the next although there are only a few seconds in between… This might also be a reason there is no RTK. Maybe you have to check your antenna connection/placement.
By the way: Could you state which receiver you are talking about when giving pictures or messages? I think for the recent posts you always took output from Moving Base (Receiver B) as described in the picture from NavSpark.
One thing I have to add: You are using GNSS-Viewer v. 2.1.012. There is already v. 2.1.026 out. Dont know if that makes any difference.
http://navspark.mybigcommerce.com/content/GNSS_Viewer-CustomerRelease-2.1.026.zip