Hi DIY.

Thanks for providing such a great forum for exchanging experience with arial drones. This has already proven a very helpful resource. I'm working on a Makani like kite energy project, but for now I'm just trying to get my Wing Wing Z84 out flying with Telemetry.

I'm currently in (Shenzhen, China) so of cause I got some 3DR V2 like Telemetry radio. My Radio works perfectly fine when I put them both in my laptop using the micro USB.

The main problem is that when I plug in my radio to the Pixracer, then it enters Bootloader more (solid red LED) 97% of the time. Appox. 1/30, it will connect with solid green and work transfer data nicely. I have attached a screenshot of the radio settings from AMP Planner 2.0. I currently have a 1.5.0 Dev version of the PX4 flight stack on the Pix Racer, but I have also tried with the official 1.4.4 available through qGroundControl.


Also a picture showing a test setup with red light on. If I just apply power it will also light up red (5V and ground connected).

Is this a fault with the radio, or is there some settings in the PX4 software that I can change to avoid this problem. I did see for ArduPilot (which i'm not using), that it's possible to put in a delay before telemetry data is being sent.

Any input would be appreciated. Would also liked to be a bit more informed, if I need to try to return it to the Chinese seller.  Thanks! Hope you can help me get going so I can contribute the community later.

/Andreas

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Just a small update.

I took one of the radios from another build (looks like 3DR v1) and soldered on the JST GH connector. Works great with the pixracer. I will try and return the radios if possible as they seem faulty.

/Andreas

Hi Andreas. From the photo it looks like you have a Pixracer set from Thanksbuyer. The set comes with a pair of telemetry radios with 4-pin connectors. The radios seem to work when connected via USB, but they go into bootloader mode (solid red) when connected via the 4-pin connector.  Did you ever identify the problem?  Thanksbuyer continues to sell these radios as part of the Pixracer set. We now have a large stack in the corner that have never worked. Thanks. Ron

Nope, I never resolved the issue. I did send the radios to seller, but never received any feedback (to my knowledge) - It can be pretty difficult navigating Taobao! My assumption is that there is a small mistake on the print, perhaps the pin that determines to bootload is floating or something similar - (considering that it would sometime work).

I would definitely try make sure to order a different set next time.

Haven't had any problems with the pixracer so far!

Thanks for the update. I will take one apart and look at the 4 pins. 

I resolved the problem. The radios have an error in the PCB causing CTS to pull low on boot from the 4-pin picoblade connector.. If you pull the plastic housing off and pry off the metal can, you can access the UART chip. Identify the CTS and cut the trace. Then the radio will work fine. It takes about 10 minutes to make the correction. Best advise is to not purchase these radios, but the diagnostics was fun.

Great that you got it to work. Hopefully it will be useful information who ever receives the rest of production batch :)

Ronald, hi. I'm an unfortunate owner of the exactly same 3DR telemetry module, ordered at banggood. When I connect main battery to my quadcopter, the telemetry module goes into Bootloader mode, and red LED goes solid.

May I ask your kind help, to post the photo of the UART chip on the module without the metal cap, and specific trace/leg on the chip/PCB, which must be cut.

It's much easier for me to go to the nearby laptop or mobile service center, than send this module back to China. I can ask the service engineer to desolder the cap and cut the trace, but I need to show them what exactly they need to do. If you can share a photo - this would make things much-much easier.

Also have you tested this solution yourself?

Thanks in advance!


Ronald Pandolfi said:

I resolved the problem. The radios have an error in the PCB causing CTS to pull low on boot from the 4-pin picoblade connector.. If you pull the plastic housing off and pry off the metal can, you can access the UART chip. Identify the CTS and cut the trace.

Hi Dmitry.  If you study the telemetry radio you will find it is designed such that "you can force bootloader mode by shorting the CTS and GROUND pins on the radio while powering on." The problem with this radio is that CTS is connected to the UART such that the voltage on CTS is pulled down during startup. You can "fix" the radio by cutting the trace between CTS and UART. Unfortunately I did not take a photo before gluing the radio back in the case, but you can find schematics and photos online, and it is easy to follow the trace for the CTS to the UART. I went through the process of evaluating the problem and executing a repair for fun. Otherwise it is not worth the effort. My suggestion is you dedicate the radios as "ground radios" and use other radios for "air radios." 

Ronald, thank you very much. Your solution worked. We identified CTS pad on the PCB of the radio module, and cut the trace to it. Now the radio module starts fine when I plug in the battery to the quadcopter.

For those "lucky" guys who end up with the same radio modules, here's the photo of the trace you need to cut. It's the trace which comes to the third contact pad from the right. when you look at opened module under the metal cap.

Thanks for including the photo. If you can send the photo to Andy Vo at Thanksbuyer (thanksbuyer@aol.com) he will attempt to negotiate a fix with the manufacturer. These radios have been shipped all over the world in 433 and 915 MHz variants, and none of them work (as air radios) without this time consuming repair. Most go straight in the trash.

Thanks for providing the photo of the fix, I just bought a pair of these 915mhz with the same problem described above.  I made the fix, they did a real good job of soldering to the CTS pad.  I will be doing the other one to also use it as an air radio, I have the radios that came with my APM 2.8 and will continue using the ground radio that came with it.  For the radios I have it was a matter of making sure the solder joint between the pad and the radio CTS pad was also cut.  

Thanks All,

I had the the same issue and used this procedure. Its all working now. Unfortunately Banggood was no help.

Dmitry Ovcharov said:

Ronald, thank you very much. Your solution worked. We identified CTS pad on the PCB of the radio module, and cut the trace to it. Now the radio module starts fine when I plug in the battery to the quadcopter.

For those "lucky" guys who end up with the same radio modules, here's the photo of the trace you need to cut. It's the trace which comes to the third contact pad from the right. when you look at opened module under the metal cap.

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