No radio waves emission on Lopy4

Reply to No radio waves emission on Lopy4 on Fri, 28 Jun 2019 07:14:51 GMT

cyby — Fri, 28 Jun 2019 07:14:51 GMT

Hello,

I bought a Lopy4 card with the V3 expansion card to connect to Lora in LoraWan mode. I also have a gateway to make a private network.
I updated the firmware of the lopy4 card by specifying the 868Mhz frequency band.
I used the Lorawan example with OTAA activation to program the card.
I had two experiments, one with the private gateway and the other with The Things Network.
In the first case I used a personal AppEUI and AppKey declared in the gateway and
in Lopy4 and in the second case I used the values provided by TTN after account configuration and declaration.
I didn't succeed in connecting, the Lopy4 looped permanently on'lora.has_joined()'.
I used a field meter to measure the radio emission on the Lopy4 antenna and I get 0 v/m !
I used another antenna and another Lopy4 card and I have the same result!
It seems there is no radio emission.

Is there a step I missed to validate radio emission ?

Or any other idea?

Thank you for your help

Reply to No radio waves emission on Lopy4 on Fri, 28 Jun 2019 07:32:43 GMT

robert-hh — Fri, 28 Jun 2019 07:32:43 GMT

@cyby After calling Lora.join() you should see the join messages every 15 seconds. The RF signal itself is short, depending on the SF setting just a burst for 70 ms at SF7 (default) up to about one second for SF12, and the power is low, 20 mW max. I do not know the sensitivity of of your field meter, but it has to be able to capture this signal.

Reply to No radio waves emission on Lopy4 on Fri, 28 Jun 2019 12:52:53 GMT

cyby — Fri, 28 Jun 2019 12:52:53 GMT

Hello
Thank you for your answer

My Champ Meter is very basic and its accuracy is about 1v/m.
I did a new test with an SF of 12 at initialization and I don't see any manifestation at the antenna either . My gateway generates 50 v/m at about 50cm and I imagined that this would also be noticeable on the Lopy4 at least during its activation sequence.
If I measured the electric field it is because I can't connect to either my gateway or TTN and I think I have met all the conditions: DevEUI declaration on the Gateway/Server side, matching of AppEUI and AppKey between the gateway/server and the device.
Moreover the example provided for the Lopy4 is very clear and simple!
CT

Reply to No radio waves emission on Lopy4 on Fri, 28 Jun 2019 13:08:45 GMT

robert-hh — Fri, 28 Jun 2019 13:08:45 GMT

@cyby Even when DevEUI and AppEUI are wrong, OTAA join will send the join requests. Only it may not get a response.
You may try also ABP for initialization. Then you can send arbitrary messages at the pace you like.
And just for confirmation on simple question (and I'm a little bit shy to ask): did you connect the antenna to the right U.FL connector?

Reply to No radio waves emission on Lopy4 on Fri, 28 Jun 2019 14:30:05 GMT

cyby — Fri, 28 Jun 2019 14:30:05 GMT

@robert-hh
No problem for the question about antenna :)

Yes, I connected it.
I have experience in radio, not LoraWan. I know that it is destructive to transmit without load (antenna) connected to the radio output amplifier.

I'm going to try ABP activation.

Thanks

Reply to No radio waves emission on Lopy4 on Fri, 28 Jun 2019 17:10:45 GMT

jcaron — Fri, 28 Jun 2019 17:10:45 GMT

@cyby I think @robert-hh meant the right connector among the 3 présent on the board (there’s one for WiFi/BLE, one for 868 and one for 433 MHz). It’s easy to mistakenly connect the antenna to the wrong one.