Communication problem between base and rover

[Francis Dominic]

Hi 

I tested the Piksi RTK module + Tallysman TW2710 external GPS antenna with two laptops (one - base ; other - rover).

I was able to immediately get a sat count of 10 in both but the rover and base are not communicating with each other.

I have attached the screenshot of the observations tab in piksi console for your reference.

What setting changes will enable the RTK fix ? 

[Clive Turvey]

You'd want to review the FAQ and forum posts related to radio connectivity.

[rai gohalwar]

Hi Francis

Are you using radios that came with the kit for communication between the 2 Piksi units ? 

If so, then no settings need to be changed. The default AT commands should configure the radios to pair and communicate with each other. 

There are a few ways to trouble-shoot where the potential problem is. The RED led on Piksi will blink when it receives observation messages from the base. Moreover, radios such as 3DR and RFD900+ will display a solid green light when they are paired with another radio. 

Like Clive mentioned, refer to the FAQ here : http://docs.swiftnav.com/wiki/Frequently_Asked_Questions

best

Rai Gohalwar 

[Francis Dominic]

Hi

I did test with the radio and I got a solid green light.

For my stand alone setup, I have attached the settings of my base and rover.

Do let me know if any changes need to be made

[rai gohalwar]

Francis,

From the pictures, the settings look fine to me. Could you do one more thing. When you open the console with Piksi connected (both base and rover), select "Info" from the drop down on the far right (log level filter). Then go to the Advanced tab and click the "Reset Piksi" button. After a while the bottom status tab in the console should say the following:

Radio found on UartA, sending configuration string.

No Radio found on UartB.

If the console says "not found" for both Uart ports, this means that there is a wiring or a baud miss-match problem with the radio and Piksi.

Best

Rai Gohalwar 

[Francis Dominic]

Hi Rai

I followed your instructions for both the base and rover,

I get message

No telemetry radio found on UARTB, skipping configuration.

No telemetry radio found on UARTA, skipping configuration.

How could I bind 2 radios together on the piksi ?

Thanks

[Clive Turvey]

I agree with Rai, the issue seems to be either the way you have these radios wired up, or the default baud rates they are configured too.

Perhaps you can detail the radios you have, how they are wired to the Piksi (how the supply, tx, rx are connected), and if you have configured or changed the settings for them. If it is easier, take a clear picture of the set up at the base or rover. Either end it doesn't matter, as neither seem to be working currently.

UARTA is primarily used to link the base/rover.

UARTB is a secondary port, you can direct different messages there, I for example have the rover configured to output NMEA, and have a BlueTooth module attached.

[Francis Dominic]

Hi Rai

I could bind both radios by configuring their net id and baud rate using mission planner or is there a simpler way of doing so.

[Francis Dominic]

I even tried using another telemetry pair by the name of holybro (http://www.getfpv.com/holybro-100mw-fpv-transceiver-telemetry-radio-set-433mhz.html) 

Though both telemetries (base and rover are lit solid green), a proper communication is not being established. 

[Clive Turvey]

Do they work at the prescribed baud rate when connected via USB?

Review carefully the wiring of the cables, they are not all the same.

[Francis Dominic]

Yes they do

Would I have to change the net id in the "Settings" tab

[rai gohalwar]

Francis, if the baud of the radio and Piksi's uart port don't match, there will be no communication between them. I would recommend you used mission-planner to set the baud of your radios to 57600. Once the baud rates match, piksi will automatically configure the rest. 

Best

Rai Gohalwar  

[Francis Dominic]

Hi Rai

In the "Settings" tab of Piksi console, should I mention anything about the telem IDs in the telemetry settings.

[rai gohalwar]

Francis,

you can if you would like. By the default the setting string will set the id to 25. If you want to change the if, you will need to add "ATS3=id#" . so for example ATS3=15

Best

Rai Gohalwar

[Francis Dominic]

Thanks Rai

Will try it out

I could make use of the PIksi - 3DR radio cable for connecting the "Holybro 433 MHz" telem with the Piksi  ?

[Clive Turvey]

>>I could make use of the PIksi - 3DR radio cable for connecting the "Holybro 433 MHz" telem with the Piksi  ?

It looks like it is supposed to, but given you are unable to talk to the radios you'd want to verify the wiring/connectivity is correct.

[rai gohalwar]

Francis,

"Configuration is also possible through the 3DR Radio configurator and AT commands." - from the getfpv holybro radio product page

Just to emphasis on clive's point. Yes, the holybro radio will work just like the 3dr radio. However, the wiring will be different from the 3dr radio. 

Best

Rai Gohalwar

[Clive Turvey]

It is potentially different, and with problems associated with connectivity it is a check-list item I'd look at.

I've rewired a number of radios with 5-pin headers which don't match the Piksi configuration. There are several "standards" used for APM and PX4, and people in China that make up their own connectivity or mirror connectors when copying board designs.

[Francis Dominic]

How do I connect the Holybro radio with the Piksi.

[Clive Turvey]

I don't have your radios so you're going to have to take some ownership/initiative with the problem

RADIO SIDE (3DR v2)

1 5V

2 RX (IN)

3 TX (OUT)

4 CTS

5 RTS

6 GND

PIKSI SIDE

1 GND

2 RX (IN)

3 TX (OUT)

4 3V3

5 5V

The Piksi TX needs to get to the Radio RX, and the Radio TX to the Piksi RX, and have the 5V and GND supplies connected correctly.

The default baud rate should be 57600 baud, and it can configure from there.

[Francis Dominic]

Quite helpful

Thanks !!!

[Francis Dominic]

My radio telem follows the same footprint as the 3DR Radio

I believe I could use the cables that came with the Piksi

[Francis Dominic]

Hey 

Thanks so much

My standalone Piski setup is working successfully

I am very much impressed with the technology that you guys have developed. Hats Off!!!

I will be now integrating it with the Pixhawk and will need your help when I faca challenges

[Francis Dominic]

Hi

I integrated the Piksi with the Pixhawk but the issue is that I am not able to see the "RTK Position" in "Solutions" tab

but in "Baseline" tab, it shows Float and then Fix

I made the following setting for the Rover Piksi,

ection	Setting	Value	Notes
UART B	sbp message mask	65280
UART A	baudrate	57600
solution	soln freq	5	(5 solutions per second)
solution	output every n obs	1
telemetry	configuration string	AT&F,ATS1=57,ATS2=64,ATS3=50,ATS5=0,AT&W,ATZ	Sets the NetID of radio to 50 (from default of 25)*

Following settings for Pixhawk,

Param	Value	Notes
GPS_TYPE2	1	Auto protocol discovery mode
SERIAL4_PROTOCOL	5	GPS Mode
SERIAL4_BAUD	115	Baud rate of 115200
GPS_SBP_LOGMASK	-1	All messages logged*
GPS_AUTO_SWITCH	1	Switch to GPS reporting best fix for vehicle control.*

And finally for Base Piksi

Section	Setting	Value	Notes
Surveyed Position	latitude	<determine this value>	This value must be as accurate as possible
Surveyed Position	longitude	<determine this value>	This value must be as accurate as possible
Surveyed Position	altitude	<determine this value>	This value must be as accurate as possible
Surveyed Position	Broadcast	True
solution	soln freq	5hz
solution	output every n obs	1
sbp	obs message max size	102
UART A	baudrate	57600
telemetry	configuration string	AT&F,ATS1=57,ATS2=64,ATS3=50,ATS5=0,AT&W,ATZ	Sets the NetID of radio to 50 (from default of 25)*

The screenshot of RTK position tab and Baseline tab

And in Mission planner

Another question, could we fly the drone when the RTK is in Float and GPS2 STATUS is 4 ?

Under what conditions would we establish the GPS2 STATUS greater than 5 ?

[Clive Turvey]

As indicate in the Pane you need to provide the Base with a surveyed position for the Rover to take its "Relative" position and convert that into a Latitude, Longitude, Altitude position with respect to the Base.

ie you have to figuratively nail the base to a known location to project that known location somewhere else.

[Francis Dominic]

I mostly get the lat, long, alt from the "Single Point Position" under Solution tab

Is that the way to do it ?

[Clive Turvey]

Look, if you want centimetre accuracy you don't take you don't take numbers yielding multi-metre level accuracy as a reference point. And you don't average numbers a metre off target. A lot of people do it that way, the results are unsatisfactory.

If you want imagery with strong registration to *local/current* Google Earth passes, then find a visual reference point (corner of structure/fence, crossed lines painted on a parking lot, etc) for the placement of the base antenna. This tends to be good when impressing management types as they can "see" it is super accurate.

The standard way to get accurate survey grade location for an antenna is to post-process measurements, 20-30mins, against a local CORS within 5-7 KM of your site, or from similar contemporaneous measurements you've taken from a reference monument or marker of documented location in the datum we are using here (WGS84)

[Francis Dominic]

Hi

How come I am able to see the "RTK Position" tab under "Solution" for the stand-alone setup but not when it is connected with the Pixhawk ?

[Clive Turvey]

Does it expect you to be sending NMEA via UARTB?

[Francis Dominic]

Pls check if the settings on the drone and ground are correct

[Clive Turvey]

I'm not involved with PixHawk integration, perhaps others can assist you in that regards.

[rai gohalwar]

Hello Francis,

Sorry for being out of the loop.

So your settings look fine to me. The solution tab will not show your RTK position (Its something that is). Your baseline tab shows "RTK Fixed" so we know that the system is working. 

As far as mission planner goes, does your system achieve "GPS Status 4" ? If so then everything is working fine. You just need to wait for the rover piksi to solve for all the ambiguities. Once thats done, the status will change to 5. You can fly in 4 if you like. Most of the times, the reason a status will stay is 4 will be due to a low satellite count. How many satellites in average do you track on your uav ? Are you using the GPS antennas that came in the kit ? 

To check the UAV's GPS status, you can click on the "STATUS" tab on the mission-planner landing page. A list will appear and the messages showing Piksi data will be : GPSStatus2, LAT2, LONG2, ALT2, SATCount2, etc. 

Best

Rai Gohalwar 

[Francis Dominic]

Hi Rai

Thanks 

I am able to track about 8-10 common satellites and the GPSStatus2 oscillates between 1 and 4

I am not using the GPS antenna that came with the kit but instead Tallysman TW2010 antenna which seems 

to be a good catch.

[Francis Dominic]

Hi

I have attached my Hardware setup

Pls give your suggestions on  the setup. 

What are all the important points to be kept in mind while placing the Piksi on the Pixhawk ?

[Francis Dominic]

Hi

Kindly provide suggestions on the hardware setup.

[rai gohalwar]

Hi Francis,

Your hardware setup is fine. Though the piksi is literally beside the pixhawk without any sort of shielding, the fact that you are tracking 8-10 common satellites ensures a lot of hardware techniques. 

I just want to mention that if your status is oscillating between 1 and 4, this means that there is an issue with the radios. Under most cases, if the rover piksi doesn't receive a full observation message from the base for more than a second, the status drops to 1. I think there is a robustness issue with your radios. 

Best

Rai Gohalwar 

[Francis Dominic]

Hi Rai

I was thinking of solving the radio issue by injecting Piksi on the main telemetry stream through Mission Planner  

[Francis Dominic]

I am following the alternate radio setup

I followed the steps as mentioned in the tutorial

1. Starting the Ground station Piksi

2. Configuring the radios

3. Settings in mission planner (Inject GPS button) 

Accordingly, I got the " waiting for UDP packet" message and it went away as soon as UDP packets started to be sent.

How do I calrify that the setup is working

For I am not able to see any changes in "GPS_STATUS2" or Piksi console

My setup is as follows,

[Francis Dominic]

HI

GPS injection is finally working

I had to change over to Mission Planner 1.3.38 and am able to get the GPS_STATUS2 as 5. 

I believe the Piksi radio was the issue and delaying the RTK FIX