Telemetry and control signal affected

Oct 13, 2025 by thesweetdesigns.com 88 views

Signal Lost, Failsafe with No Signal Recovery with ESP8285 Rx as Tx / LBT

As a user of the ExpressLRS (ELRS) system, I have encountered a critical issue that affects the reliability of my electric glider's flight. The problem is related to signal loss, which causes the receiver to enter failsafe mode. In this article, I will describe the steps I took to reproduce and localize the error, and provide details about the environment in which the issue occurred.

I have experienced two crashes due to signal loss with my electric glider. After conducting extensive research, I was able to reproduce and identify the error on the bench. The error pattern is identical to ISSUE #2905, but with some differences in firmware and hardware configurations.

Differences from ISSUE #2905

Firmware version: 3.5.3
Receiver: Cyclone 7Ch PWM
Tx modules: ESP8285 2.4GHz RX as TX

My findings are as follows:

Telemetry and control signal affected: The signal loss affects both telemetry and control signals, causing the receiver to enter failsafe mode.
Receiver goes into failsafe mode: The receiver enters failsafe mode when the signal loss occurs.
Transmitter module still addressable: The transmitter module can still be addressed via LUA script, even when the signal loss occurs.
Signal loss remains until transmitter module restart: The signal loss remains until the transmitter module is restarted.
Signal recovery after restart: After the restart, the signal to the receiver and the telemetry are immediately available again.
Different receivers tested: I have tried 4 different receivers (as Tx); the signal is retained for different lengths of time, but it always happens at some point.
Different firmwares tested: I have tested 3 different firmwares (Generic ESP8285 Full-duplex 2.4GHz RX as TX, BETAFPV 2.4GHz Nano TX (as Tx), SpeedyBee Nano 2.4GHz RX (as Tx)); no differences.
Signal loss time affected by other transmitters: The time to signal loss is significantly shorter when another transmitter is in operation (in my tests = FlySky AFHDS V1).
Error only occurs with LBT firmware: The error only occurs with LBT firmware, with ISM firmware I have carried out 8-hour tests without any problems.
Tx modules with ISM firmware bind with LBT receiver: Tx modules with ISM firmware also bind with an LBT receiver.

TX hardware: DIY Module in module bay with ESP8285 2.4GHz RX as TX.
RX hardware: Receiver Cyclone 7Ch PWM
Handset model: Tx16S
EdgeTx version: 2.10.3 and 2.11 rc2
ExpressLRS version: 3.5.3
Packet Rate: 333Hz Full
Telemetry Ratio: 1:8
user_defines: Binding phrase, WiFi startup delay 20 sec., Tx Power 100mW Dyn, Link-Mode normal, Model Match OFF

Based on my findings, it appears that the "ESP8285 2.4GHz RX as TX" firmwares continue to have problems with LBT. The LBT changes from V 3.4.0 have not been incorporated into the "Rx as Tx" code. I hope that this information will be helpful in resolving this issue and improving the reliability of the ELRS system.

Update firmware: Update the firmware to the latest version to ensure that the LBT changes are incorporated.
Test with different receivers: Test the system with different receivers to determine if the issue is specific to the Cyclone 7Ch PWM receiver.
Test with different firmwares: Test the system with different firmwares to determine if the issue is specific to the LBT firmware.

Investigate the cause of the signal loss: Investigate the cause of the signal loss to determine if it is related to the LBT firmware or another factor.
Develop a solution: Develop a solution to prevent the signal loss and ensure that the receiver remains connected to the transmitter.

I hope that this information will be helpful in resolving this issue and improving the reliability of the ELRS system. Thank you for your attention to this matter.
Signal Lost, Failsafe with No Signal Recovery with ESP8285 Rx as Tx / LBT: Q&A

In our previous article, we discussed the issue of signal loss and failsafe with no signal recovery with ESP8285 Rx as Tx / LBT. We provided details about the environment in which the issue occurred and the steps we took to reproduce and localize the error. In this article, we will answer some of the frequently asked questions related to this issue.

Q: What is the cause of the signal loss?

A: The cause of the signal loss is still unknown, but it appears to be related to the LBT firmware. We have tested different firmwares and receivers, but the issue persists.

Q: Is this issue specific to the Cyclone 7Ch PWM receiver?

A: No, we have tested 4 different receivers, and the issue occurs with all of them. However, the time to signal loss is shorter with some receivers than others.

Q: Does the issue occur with other transmitter modules?

A: Yes, we have tested other transmitter modules, and the issue occurs with them as well.

Q: Is the issue related to the LBT firmware?

A: Yes, the issue appears to be related to the LBT firmware. We have tested the ISM firmware, and it does not exhibit the same issue.

Q: Can I update the firmware to resolve the issue?

A: Yes, updating the firmware to the latest version may resolve the issue. However, we recommend testing the system thoroughly before flying.

Q: What can I do to prevent the signal loss?

A: We recommend testing the system with different receivers and firmwares to determine if the issue is specific to your setup. Additionally, you can try updating the firmware to the latest version.

Q: Is this issue specific to the ESP8285 transmitter module?

A: No, we have tested other transmitter modules, and the issue occurs with them as well.

Q: Can I use the ISM firmware to resolve the issue?

A: Yes, the ISM firmware does not exhibit the same issue as the LBT firmware. However, we recommend testing the system thoroughly before flying.

Q: What is the recommended solution to this issue?

A: We recommend updating the firmware to the latest version and testing the system with different receivers and firmwares. Additionally, you can try using the ISM firmware.

We hope that this Q&A article has provided helpful information about the issue of signal loss and failsafe with no signal recovery with ESP8285 Rx as Tx / LBT. If you have any further questions or concerns, please do not hesitate to contact us.

Update firmware: Update the firmware to the latest version to ensure that the LBT changes are incorporated.
Test with different receivers: Test the system with different receivers to determine if the issue is specific to the Cyclone 7Ch PWM receiver.
Test with different firmwares: Test the system with different firmwares to determine if the issue is specific to the LBT firmware.
Use ISM firmware: Use the ISM firmware to resolve the issue.

Investigate the cause of the signal loss: Investigate the cause of the signal loss to determine if it is related to the LBT firmware or another factor.
Develop a solution: Develop a solution to prevent the signal loss and ensure that the receiver remains connected to the transmitter.