Bosch TPS110 parking sensor OTAA works, but subsequent downlinks fail

Hello, recently I bought some of Bosch TPS110 parking sensors and I would like to obtain communication using The Things Network but unfortunatelly there is some issues connected with proper communication. After successful join procedure device don’t get acknowledge to the initial message which results in communication fault and restart. Do these sensor are still compatible with TTN platform? Maybe there is any other know issues with this platform? i attached some sample message log for this sensor.

Application data

Gateway traffic

You’re seeing:

  • You’re using EU868.

  • The downlink for the Join Accept, which is using spreading factor SF10 and bandwidth BW125, is received just fine, as a few moments later the device starts sending uplinks using the newly assigned DevAddr and the new session secrets. (The DevAddr and secrets change for each new OTAA join. You can see the DevAddr in TTN Console, and you know the device uses the expected secrets as TTN is accepting the uplink messages.) This downlink uses the same frequency as the Join Request uplink, so for EU868 indicates that RX1 was used.

  • Subsequent downlinks on 869.525 SF9 BW125 are not received. This frequency is only used for RX2 in EU868, and is specific for TTN; the default for RX2 in EU868 is SF12. For EU868 this specific setting is included in the Join Accept downlink that was clearly received by the device earlier, so SF9 is to be expected for RX2 indeed.

Some possible causes:

  • Maybe the device does not correctly process or store the network settings that are included in the EU868 Join Accept, and is erroneously still expecting the default SF12 for RX2. Ask the manufacturer if they think this should work.

  • Maybe the device is just too far from the gateway to receive the SF9 dowlink. (Note that its uplink used the slower SF10.) However, the gateway will be using a higher transmission power to make up for using the lower SF9 instead of the default SF12.

  • Maybe the gateway does not support the specific power settings that TTN asks it to use for the downlink. What gateway are you using? See ERROR: Packet REJECTED, unsupported RF power for TX - 24.

  • Maybe the downlink is received by the gateway too late to be transmitted, due to high network latency. However, then the Join Accept downlink would likely have failed too. How is the gateway connected to the internet?

For testing, you might be able to avoid RX2 if you can make the device use a better (so: lower) spreading factor for its uplink. Anything that you can configure?