Hi @TheLazy, Ah, let me see. Let me first summarize you situation. (1) Your radios are configured and connected, and testing sending/receiving commands looks OK, as indicated by the green and red LEDs. (2) Now suppose the ground module sends a text message "HELP <new line> ", and air module receives the message OK. (3) You problem now is how can Rpi connected to the air module display the received text message "Help <newline>", in the terminal window. Please confirm if I understand you situation and problem correctly.

And can you give me the web links to your radios, any user guide or tutorials you are following, like the following? (1) AliExpress 3DR 500MW Radio Telemetry 433Mhz 915Mhz Air and Ground Data Transmission Module for APM Pixhawk Flight Control FPV - US$25, aliexpress.com/i/32799841052.html (2) 3DR V2 Quick Start Guide, 3dr.com/wp-content/uploads/2013/10/3DR-Radio-V2-doc1.pdf.

Hi @tlfong01, Your understanding is correct. I want to display the message <HELP> sent from ground module (using mission planner) on the Raspberry pi terminal at air module end. The 1st web link shared by you is the radios I am using. I am not following any specific tutorial/ guide. Its just bits and pieces from the internet which we followed and made upto basic stage of connecting the radios and verifying it.

Hi @TheLazy, Oh my goodness. You must read the friendly manuals. I don't talk to lazy guys not reading anything. Now read this PX4 stuff and let me know what do you think about it. "PX4 Autopilot User Guide": docs.px4.io/master/en/index.html.

Hi @tlfong01. Thanks for sharing the good resource. I went through the basic concepts which led me to Sik telemetry section giving a tutorial of connecting the radios to TELEM1 port of the controller such as Pixhawk/Navio and proceeding further with build instructions. The problem is I don't have the Pixhawk/Navio controller board. I am trying to interface the airmodule radio directly to the Pi board (Without controller board) and read the data. Please let me know, if I can achieve this without a controller board or It is must to have the controller board in order to proceed.

Hi @The Lazy, Good, so you have a rough idea that the air radio can connect to a PixHawk controller. I agree with you that your question actually has nothing to do with any controller. In other words, you only need the ground and air radio module to answer your question. Furthermore, if the near term goal is to use Rpi to talk to the air module using UART, then even the ground module is not required. / to continue, ...

You only need to (1) use the Misson planner to config the air radio, (2) Connect Rpi UART to the air radio and start talking. If you agree what I am suggesting make sense, then we can start studying this little "Rpi > UART > Air Radio Module" project. Questions, comments, and counter suggestions welcome.

I agree with the suggestion. My ultimate goal is to decode the data received from the ground module using Rpi > UART > Air Radio Module.

OK. So we agree that (1) Ultimate goal is to use Rpi to decode the Air module's received data sent from ground module. (2) Near term goal is (a) How can Rpi start talking to the air module, (b) Where to find the data sent by the ground module, (c) How to decode the data. Now we can start with (a). But let me know if (a), (b), and (c) are all the "user requirements". Please feel free to let me know any other requirements before we start (a).

Now a couple of questions: (1) Do you have any experience in: (a) Rpi4B Thonny 3.2 Python 3,73? (2) Do you know how to test loopback of (a) Rpi on board UART (using GPIO TxD, RxD pins), (b) USB to UART TTL serial /adapter/cables? (2) Do you have any other relevant experience, eg, Arduino/Rpi HF/RF devices such as SIM800, GPS, or BlueTooth serial module using UART for config and testing?

lunch time. see you later. cheers.

I have experience with python 3.7 language. Have worked with arduino, gsm800 interfacing with arduino. Blue tooth. I don't know to test the loopback part.

(1) Any user experience with terminal emulators, such as Win/Linux/Rpi/Arduino RealTerm, TeraTerm, SuperTerm, puTTY, miniCom, cuteCom? (2) Basic handshaking protocol dialogue such as "AT <new line>, OK <new line>"?

Ah, you remind me that I once played with Arduino RF12B 433MHz transceiver. I wrote Arduino IDE C++ programs to interface with SPI RF12B and talk UART. So I guess you have not played with 433MHz RF12B, or something similar, have you?

I have experience with Teraterm, At commands used for testing blue tooth module. I have not worked with 433MHz RF12. Can we have conversation over email?

Ah, when our comments get too long, system will invite us to a chat room, which is more friendly and flexible than using emails. The bad things of using emails are (1) other visitors can not join in, (2) future visitors cannot check past record. So let us use comments for a longer while.

I did not know about the comments part. I completely agree with you.

Ah, I used Win10RealTerm to talk UART with BlueTooth serial module, which in turn talks BT with android phone. And about loop back, if you connect the TxD to RxD pin and use TeraTerm to send something eg, "XYZ' and "XYZ" is displayed "echoed" back in the TeraTerm terminal, and this is loopback test, testing the wiring is OK. Now if you have not used python to do loopback/echoback, then you might need to learn this later. But actually you can use Win10TeraTerm/RealTerm to try to talk to the air radio. Win10 as a developing host is faster than using the stupid Rpi puTTY/minTerm.

Ok give me some time, I'll try to talk to airmodule using loopback on raspberry pi using minicom (similar to teraterm). Ill test and give the feedback.

One thing about comments: (1) You are not supposed to use answer as a comments, but a get around perhaps is to give an interactive, progressive, Agile style, muddling through tentative answer, as my suggested edit to your answer. (2) So you can report your TeraTerm experiment in your answer, and if successful, then proceed to read the received data (sent by the ground station) and see how to analyse it. Take you time. No hurry at all. Good luck and cheers! :)

One more thing: In case you carelessly forget, the WinTeraTerm connection is "crossing over" / (also called "null modem"): TxD this side connected to RxD opposite side, and RxD this side to TxD opposite side. Now this is not loop/echo back, because TeraTerm sends "AT", and air module returns "OK". It is two parties talking, not one party looping back. :)

I am suggesting some editing to your answer, in a way that future FPV radio newbie visitors might hopefully find your answer useful to learn the basic things. Of course it is your answer, so feel free to accept, modify, or reject (just delete it! :)) any of my edit suggestions, to fit your elegant personal styles.

I found a terminal mode Mission Planner tutorial (Ref 8) you might find useful. I guess the air module has two connectors, USB and UART. The USB connector is for Windows only Mission Planner. For Linix and Rpi terminal mode, you use the UART connector. But I am only 50% sure. And in case you would like to use python UART to talk to the air module, you might like to read Ref 9, 10 for UART talking to GPS and LIRC, and also python UART loopback test program.