Hey @geofrancis,
I’m also interested in testing out these cheap SkyTraq RTK receivers. Quick question since you have one on hand, Is the SMA connection on the PCB normal or reverse polarity and is it male or female?
Thanks
Its an SMA connector, without the pin.
Thanks for the quick reply.
Just want to make sure they didn’t do something weird and add what’s known as a reverse polarity connector on the board. Which of these is it?
Edit: I guess by process of elimination it’s #2 since you said no pin and the pictures on navspark show the male threads.
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I’m interested if you get it working and if you are getting close to centimeter accuracy. I looked at ordering one too and shipping was $60 to the states so I balked. If it works, I might order 2 for a L1/L5 basestation since I am pushing the limits of the free ntrip provider. I think they would be more popular without 60 bucks for shipping.
That is the only place I have seen L1/L5 and centimeter accuracy without the L2. In fact I was going to make a post and ask if it was even possible because my google-fu is failing, and it seems like L5 would be better for a mowbot with the trees.
Long story short i managed to damage my receiver when a ground wire came loose on the 3.3v regulator when i was testing it on breadboard and it got pulled up to 5v killing it. Im going to order another 2 soon since shipping is so high i might as well.
It was qorking up until that point, i never got testing rtcm injection, it got broken as i was wiring it up.
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Oh, I’m sorry!! Im a little surprised 5v killed it to be honest.
You MIGHT want to order 1 for a basestation as well.
In short, the first chart says you need 2 for heading information for a rover.
"Most RTK correction service worldwide are still L1/L2 type, so L1/L2 RTK receivers work best with 3rd party RTK correction service without compatibility issues.
Only common signals used by both RTK base and RTK rover are used for RTK computation."
Which then the chart says it even if the rtk base supports L1/L2, the 1125 ignores the L2 data completely.
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Yes it can do rtk with just l1 its just not as reliable. I wanted to see if a 50usd GPS with free rtcm would work as the cheapest possible setup. Im not doing anything critical so I dont mind some trial and error getting it working.
It isn’t as accurate or reliable. For 50 bucks you -might- be able to get two l1/l5 receivers and try to set up a basestation for rtk. Then you have the l5 signals. Butt hen you need another antenna.
I am kind of in the same boat doing about the same thing except I want 1cm accuracy and my rtcm streamer is right about at the limit for it to work properly.
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PX1172RH-HAT looks like a good choice for RTK and YAW in one package for ~$200. Cheaper and more compact than two ArduSimple boards, and a bonus - you only need to use the one serial port on the flight controller.
As long as it sends the right NMEA message for YAW to make ArduPilot happy.
I am reminded, however, that with two F9Ps we can use one for RTK position, and one for Yaw.
With this unit, we won’t know if we have a RTK Fixed Yaw only, or a Fixed Yaw + Fixed position from the base.
You won’t know when there’s an interruption in the feed from the fixed base.
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@geofrancis any latest update, also need to have a word with you regarding skytrq ? do you have discord ?
@geofrancis did you ever get these $50 Skytraq RTK receivers working? I am looking at setting up a mower and trying to cost out the most economical solution
I haven’t replaced mine after I damaged it, it’s on my list for the summer. it has been documented to work with ardupilot so i dont see any issues using it. your probably best to use a pair and run your own base station or get the l1/l2 version at 100usd if you want to use online ntrip servers as i dont think many do l1/l5.
rtcm injection over mavlink supposedly works too so you only need a single telemetry radio.
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I’m considering biting the bullet, but might go ahead and order 10 if there are others interested in splitting shipping cost. (I need 2) Of course, would be re-shipping once they arrived, but for ground shipping, would only be $7ish. So $65/10 + $7= $14ish on top of the $50 for the module.
Looking at NS-HP-GN5 : PX1125R L1/L5 RTK BREAKOUT BOARD since I’ll be running them through a ESP32. (Choosing the L5 model since enough sats should have L5 support in the next year or two, and L5 is the future. Also cheaper, since I’ll be running my own base station)
Let me know if you are interested, and if enough folks are, I’ll do an order.
@geofrancis good to see all your posts and the details which you shared about gps sensor. I am looking for a gps sensor with 1 cm accuracy. Was wondering if you can suggest me any good option, please. I am in the US, so assuming it won’t take much longer in shipping.
can someone elabrate on how the module worked out I am considering is buying a setup too - just because of cost - good price for a hobbyist but I do not want to collect another forever (parts and project) .
can someone elabrate on how the module worked out I am considering is buying a setup too - just because of cost - good price for a hobbyist but I do not want to collect another forever (parts and project) .
Sorry, I haven’t yet ordered anything. My purpose is precision surveying, and there are enough resources online that I feel pretty confident that this module will work without an issue. I just don’t foresee having enough time in the near future to invest in the project.
I purchased the PX1122R L1/L2 RTK Breakout Board back in June 2023 and combined it with a SparkFun Serial Basic Breakout -USB-C module, a Sik 915 MHz telemetry radio and a Beitian BT-160 Survey Grade L1/L2 antenna to build the Rover portion of my diy autonomous robot lawnmower.
The Breakout Board uses the Sik telemetry radio to receive RTCM correction messages from my Base Station. The Beitian BT-160 is a less expensive alternative to the Sparkfun Survey Grade antennas and provides similar performance.
I have no trouble getting and maintaining a Fix solution with the Breakout Board when used in conjunction with my Base Station. The GNRMC messages from the Breakout Board are sent over the USB-C connection to a Raspberry Pi 4B running the Donkey Car path_follow.py template which provides steering and throttle output to drive the lawnmower over a prerecorded path to mow my lawn.
Works great.
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@TCIII thanks for sharing your experience. I’d also go for a dual-freq receiver cause the L1 band can be easily spoofed or jammed.
I have a question to clarify on how to extract the precise positions after RTK corrections have been applied: do I understand correctly that once you feed RTMC messages to your rover (via the UART RX pin), you simply read NMEA messages (in particular, GNRMC) that the rover outputs?
@dizcza,
Yes, the Donkey Car path_follow.py template, running on the Rover’s RPi 4B 4GB, receives only the GNRMC message at 115200 baud over a USB connection and uses the GNRMC message to accurately determine its lat and lon position.
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