API call results "DOWNLINK_PAYLOAD_SIZE" Error because "max. payload size" = 0

ChirpStack (v4)
#1

I recently set up the latest Chirpstack V4 (chirpstack: 4.1.3_linux; chirpstack-gateway-bridge: 4.0.3_linux) and it can receive packets from node without any problem.
Then I tried the Python API following “Python examples - ChirpStack open-source LoRaWAN<sup>®</sup> Network Server” with necessary changes (server addr; token; dev_eui etc) and these two lines:

req.queue_item.data = bytes([0x01, 0x02, 0x03, 0x09])
req.queue_item.f_port = 1

However, when check from the web UI, it complains with “Device queue-item discarded because it exceeds the max. payload size”. More details as below picture shows:

max_payload_length_error
max_payload_length_error724×599 48.5 KB

Has any one seen such issue before, and how to correct it? Thanks.
A few more details:

  1. I use the CN470_RP_1B, not the RP_2
  2. The node may not receive in port 1, but I think it doesn’t matter for the issue here.

In fact what I really want to do is sending MAC command “NewChannelReq” to guide chirpstack to ask Node to change the current channel list. Now I wonder is it possible? Now I just feel that the API payload can’t include MAC command?
Thanks in advance. :slight_smile:

#2

After tested with EU868 frequency band, I don’t see this issue; and the node can receive the payload correctly.

So I guess the root cause is Chirpstack doesn’t support CN470_RP_1B? I see this is mentioned somewhere; however I can choose it from Chirpstack UI page “device profiles”. So maybe the UI should filter such option out?

#3

Could you take a screenshot of the device-profile mac-version and regional param. revision options that you selected?

In fact what I really want to do is sending MAC command “NewChannelReq” to guide chirpstack to ask Node to change the current channel list. Now I wonder is it possible? Now I just feel that the API payload can’t include MAC command?

You can not send these mac-commands. This is all handled by ChirpStack automatically. Just make sure you have configured the additional channels (see also the region_eu868.toml config example that contains 5 additional channels). Then these channels will be automatically configured on the device by ChirpStack.