How to use the standalone serial mode added in release v1.8+?

gjkm · January 15, 2025, 5:11pm

I would like to use the device standalone over serial. I would like to receive (rtl_433_esp library) and transmit FSK packages.
The released images on github does not look to be intedted for such a use.

Why is the serial console not available on the normal images? When i press any button i cant activate a console. I flashed the device over usb cable. I would like to just continue working over that same usb cable over serial.
If i connect it to wifi (i do not need/want wifi/network at the moment but i am forced to use it at the moment) then its rebooting the whole time because it does not found the MQTT - because there is none. I just want to receive and transmit data over serial. How can i disable all those things? I was not able to find something about that serial-only-usage that should be possible since v1.8.0 in the documentation.

gjkm · January 22, 2025, 4:22pm

Is it impossible to use the released firmware files on github for the advertised serial mode?

Serial Communication Mode: OpenMQTTGateway can now operate without MQTT! Modules can communicate over a Serial connection, making it easier to link multiple microcontrollers.

The only way to use it is to add -DZgatewaySERIAL=“SERIAL” and compile a new firmware? There are no firmware files to download with a browser (.bin) out there that support this serial mode?

1technophile · January 25, 2025, 1:08pm

To use serial communication layer you will need to build your own binary.
What would be the device receiving the data from the RTL_433toSerial gateway ?

gjkm · January 26, 2025, 2:32pm

A computer that had been used to install the firmware over the usb cable would be the the device receiving the data from the RTL_433toSerial.

Could you make this functionality available at default? Would be great to have the different use options already build into the released firmware files on github without the need of recompilation.

A example usecase to make things more clear:
A person is using a T-Beam with for example Meshtastic and the app on the smartphone that is using blutooth to connect to the T-Beam. The same person have a device at home that should be transmitting on the same frequency band. For example external battery powered temperature sensor sold with a weather station. Suddenly the weather station do not receive the transmission any more. So the person would like to use the SX127x from his T-Beam with rtl_433_esp library to check on his computer if the external transmitter is still transmitting to know if the issue is on the external transmitter or at the reception from the weather station.

Having to connect things to WiFi networks and having to set up some MQTT servers is just making things much, much more complex to just quickly check if a transmitter is transmitting or not.

Second usecase example at transmitting raw packages:
The person would like to know how high and how low temperatures the weather station could receive and what happens on the screen when the values are too high or too low. Instead of putting the transmitter into the oven or fridge, it would make more sense to just send the packages with high or low temperature to the weather station. This would make the need of receiving a package on a computer, understanding its format, changing the values and transmitting it again.

For both examples using just the USB cable to install the firmware files from github and then using the same cable and its serial connection to receive and transmit the data would be enough.

1technophile · January 26, 2025, 3:15pm

Sure, I did not include a ready binary to see which interest this kind of feature will have. Happy to add one.

Maybe the solution is more an offline mode in this case + the regular serial logs ?

The XtoSERIAL feature is more for machine to machine communication.

gjkm · January 26, 2025, 3:38pm

Thanks for the quick answer.

The openmqttgateway was the most active project using rtl_433_esp i could find and also the most polished one. Because of the use of RadioLib, i was hoping to be able to use rtl_433_esp for reception and RadioLib for transmission.
rtl_433 have simplified ability to show the raw data that have been received next to the decoded results. I hope rtl_433_esp work the same and i can then take a look into the raw data thanks to serial communication and having the practical decoded data on a OLED screen of the received data.

Then i liked to copy over the data-string received from it and check if at first i can transmit the same thing i received with rtl_433_esp (for example with a second t-beam) by following

github.com

jgromes/RadioLib/blob/master/examples/SX127x/SX127x_Transmit_Interrupt/SX127x_Transmit_Interrupt.ino#L81


      
            // when packet transmission is finished
            radio.setPacketSentAction(setFlag);
          
            // start transmitting the first packet
            Serial.print(F("[SX1278] Sending first packet ... "));
          
            // you can transmit C-string or Arduino string up to
            // 255 characters long
            transmissionState = radio.startTransmit("Hello World!");
          
            // you can also transmit byte array up to 255 bytes long
            /*
              byte byteArr[] = {0x01, 0x23, 0x45, 0x67,
                                0x89, 0xAB, 0xCD, 0xEF};
              transmissionState = radio.startTransmit(byteArr, 8);
            */
          }
          
          // counter to keep track of transmitted packets
          int count = 0;

byte byteArr[] = {0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF};

Then i modify this data and experiment with the values in there.

That is the whole current task at the moment and nothing there have any need of WiFi or MQTT.

Would that use-case be possible with the current implementation?

I do not know of any other software project where i could use for example a t-beam as it is that would make such a use-case possible.

1technophile · January 26, 2025, 6:37pm

A kind of range extender of RF 433 signals ?

gjkm · January 26, 2025, 9:13pm

No, its just a test to know that TX is working and what is getting out of the SX127x TX can still be decoded with the stock weather station. When that is working, start to modify the data to something else. For example higher or lower temperature and try to calculate the checksum by hand correctly to send valid data with different values.