Class C Device Downlink Not Sending Immediately #694
Description
Hi I am running a Chirpstack server 4.9.0 and cannot send downlinks to a class C device immediately after the 1st uplink.
I enabled the Class C option under the device profile.
My downlink will only be sent right after an uplink, which is a class a behavior.
The JoinAccept and the first confirmed uplink is 2 seconds apart, is this a problem?
What do I miss to enable a Class C device?
Here is the detail of my first confirmed uplink:
{
"phy_payload": {
"mhdr": {
"m_type": "ConfirmedDataUp",
"major": "LoRaWANR1"
},
"mic": [
60,
124,
133,
131
],
"payload": {
"f_port": 10,
"fhdr": {
"devaddr": "0102d274",
"f_cnt": 1,
"f_ctrl": {
"ack": false,
"adr": false,
"adr_ack_req": false,
"class_b": false,
"f_opts_len": 0,
"f_pending": false
},
"f_opts": []
},
"frm_payload": "0123456789abcdef"
}
},
"rx_info": [
{
"channel": 7,
"context": "AQID8TZ0NgGN",
"crcStatus": "CRC_OK",
"gatewayId": "0016c001f156719b",
"gwTime": "2025-06-09T17:47:58.662606008+00:00",
"location": {
"latitude": 43.8043949,
"longitude": -79.3436473
},
"metadata": {
"hop_count": "1",
"region_common_name": "US915",
"region_config_id": "us915_5",
"relay_id": "f1367436"
},
"nsTime": "2025-06-09T17:47:58.660004831+00:00",
"rfChain": 1,
"rssi": -24,
"snr": 10,
"uplinkId": 856978064
}
],
"tx_info": {
"frequency": 911700000,
"modulation": {
"lora": {
"bandwidth": 125000,
"codeRate": "CR_4_5",
"spreadingFactor": 10
}
}
}
}