Txinfo wrong frequency 1210132480

Roberto_Palermo · April 14, 2021, 9:50am

Dear all,
I’m using the ChirpStack application version 3 using docker-compose.
The gateway connected to ChirpStack is a Dragino LP-01 with the single packet forwarder. The device is an Arduino with a Dragino hat.
Frames sent by the device are received from the gateway and sent to ChirpStack, I can see them into gateway’s frames:

but on the network server logs I see the error:
“get channel error: no channel found for frequency: 1210132480, dr: 5”

This frequency is absolutely wrong, both on Dragino and on Arduino the reported frequency is 868100000 MHz.

I also tried to add this frequency into configuration, but correctly the network service notice that the frequency must be a 100 multiple.

So now I’m stuck into understanding from where this wrong frequency come: is from my Arduino device, or the Arduino packet forwarder embedded on Dragino or from Dragino itself? Or is it a wrong configuration of my gateway in ChirpStack?

Thank you in advance for any help!
Bests,
Roberto

brocaar · April 14, 2021, 9:59am

This is likely to be the frequency reported by your gateway to ChirpStack. What I recommend to do is look at the UDP data sent by your gateway to the ChirpStack Gateway Bridge.

See https://www.chirpstack.io/project/guides/connect-gateway/ for some examples to debug this.

Roberto_Palermo · April 14, 2021, 10:24am

Hi @brocaar and thank you very much for your support!
With your instructions I debugged the incoming UDP messages, but the frequency seems to be correct:

E0…@.&…
…
…6…V?..@A…{“rxpk”:[{“tmst”:546652299,“time”:“2021-04-14T10:22:43.392575Z”,“chan”:7,“rfch”:0,“freq”:868100000,“stat”:1,“modu”:“LORA”,“datr”:“SF7BW125”,“codr”:“4/5”,“lsnr”:7.8,“rssi”:-93,“size”:24,“data”:“QMtO9AGAAAAB7QLgiFHeaQUHqikQMl3L”}]}

What could be wrong?

Many thanks,
Roberto

brocaar · April 14, 2021, 2:39pm

The value itself is correct, but the presentation is wrong. It is expected to be in MHz, your freq is in Hz.

See:

github.com

Lora-net/packet_forwarder/blob/master/PROTOCOL.TXT#L136


      
          ```
          
          That array contains at least one JSON object, each object contain a RF packet 
          and associated metadata with the following fields:
          
           Name |  Type  | Function
          :----:|:------:|--------------------------------------------------------------
           time | string | UTC time of pkt RX, us precision, ISO 8601 'compact' format
           tmms | number | GPS time of pkt RX, number of milliseconds since 06.Jan.1980
           tmst | number | Internal timestamp of "RX finished" event (32b unsigned)
           freq | number | RX central frequency in MHz (unsigned float, Hz precision)
           chan | number | Concentrator "IF" channel used for RX (unsigned integer)
           rfch | number | Concentrator "RF chain" used for RX (unsigned integer)
           stat | number | CRC status: 1 = OK, -1 = fail, 0 = no CRC
           modu | string | Modulation identifier "LORA" or "FSK"
           datr | string | LoRa datarate identifier (eg. SF12BW500)
           datr | number | FSK datarate (unsigned, in bits per second)
           codr | string | LoRa ECC coding rate identifier
           rssi | number | RSSI in dBm (signed integer, 1 dB precision)
           lsnr | number | Lora SNR ratio in dB (signed float, 0.1 dB precision)
           size | number | RF packet payload size in bytes (unsigned integer)

Roberto_Palermo · April 15, 2021, 1:50pm

Dear @brocaar,
yes it is a Dragino issue, I found this discussion: Lorawan/band: unknown channel for frequency
Now I will look for a solution/workaround, but you answered my question!
If I will find a solution I will update this thread.

Thank you very much!