No downlink traffic in chirpstack from old ic880a gateways

niau33 · June 20, 2023, 3:21am

It seems that in chirpstack console we don’t see any downlinks from any of ours ic880a gateways.
They are running with udp semtech packet forwarders in docker based on that image GitHub - netceteragroup/rpi-ttn-gateway: Docker image for Raspberry PI TTN gateway based on Hypriot

Output in the gateway is:

##### 2023-06-20 03:14:50 GMT #####
### [UPSTREAM] ###
# RF packets received by concentrator: 0
# CRC_OK: 0.00%, CRC_FAIL: 0.00%, NO_CRC: 0.00%
# RF packets forwarded: 0 (0 bytes)
# PUSH_DATA datagrams sent: 1 (220 bytes)
# PUSH_DATA acknowledged: 100.00%
### [DOWNSTREAM] ###
# PULL_DATA sent: 3 (100.00% acknowledged)
# PULL_RESP(onse) datagrams received: 0 (0 bytes)
# RF packets sent to concentrator: 0 (0 bytes)
# TX errors: 0
### [GPS] ###
# Invalid gps time reference (age: 1687230890 sec)
# Manual GPS coordinates: latitude 42.36255, longitude 22.99800, altitude 660 m
##### END #####
INFO: [up] PUSH_ACK for server 78.128.42.83 received in 13 ms
INFO: [down] for server 78.128.42.83 PULL_ACK received in 12 ms
INFO: [down] for server 78.128.42.83 PULL_ACK received in 13 ms
INFO: [up] PUSH_ACK for server 78.128.42.83 received in 13 ms
INFO: [down] for server 78.128.42.83 serv_addr[ic]PULL_RESP received :)
INFO: [down] a packet will be sent on timestamp value 833701155
INFO: Downstream Packet RF power to - 14 dBm
INFO: [down] for server 78.128.42.83 PULL_ACK received in 12 ms

However in chirpstack we don’t see any downlink data:

If it is just visualization issue would be ok but in packet log in chirpstack we also don’t see any downlinks.

Our gateway bridge is version=3.14.6

brocaar · June 20, 2023, 12:24pm

If it is a really old Semtech Packet Forwarder version, then it doesn’t send the TX ACK:

github.com

Lora-net/packet_forwarder/blob/master/PROTOCOL.TXT#L322


      
          That packet type is used by the server to send RF packets and associated 
          metadata that will have to be emitted by the gateway.
          
          
 Bytes  | Function
          :------:|---------------------------------------------------------------------
           0      | protocol version = 2
           1-2    | random token
           3      | PULL_RESP identifier 0x03
           4-end  | JSON object, starting with {, ending with }, see section 6
          
          
### 5.5. TX_ACK packet ###
          
          
That packet type is used by the gateway to send a feedback to the server
          to inform if a downlink request has been accepted or rejected by the gateway.
          The datagram may optionnaly contain a JSON string to give more details on
          acknoledge. If no JSON is present (empty string), this means than no error
          occured.
          
          
 Bytes  | Function
          :------:|---------------------------------------------------------------------
           0      | protocol version = 2

In this case you do not see the downlinks in ChirpStack, as it will never receive any confirmation that the downlink was accepted by the gateway. If this is the case, then you might want to update your packet-forwarder version.

niau33 · June 21, 2023, 7:11am

Hm ok. will try to update it. In that case I assume also ADR won’t work properly, is this correct?

Could you confirm that if we try with version 4.1(latest) it will eventually work? It is really old also - from 2017

brocaar · June 28, 2023, 2:10pm

I believe the TX_ACK was introduced in v3.0.0, thus anything later should be good.