Sourcecode for Enqueue downlink payload

Ksemanov · November 18, 2022, 4:00am

Enqueue downlink payload is a GUI for that appears in the cs application server dashboard.

Applications >> Name >> Device name

Where is the sourcecode for this staged? I don’t want to copy it, rather I need to know precisely how it is calculating the downlink frequency as a function of the uplink packet frequency.

My end devices are currently using 8 channels from US915 subband 2. Ranging from 903.9 to 905.3 MHz.

chirpstack-network-server.toml has

[network_server.band] name=US915

enabled_uplink_channels=[8,9,10,11,12,13,14,15,64]

My Join/OTAA RX2 channel frequency (Hz) * =
923300000

LoRa Regional parameters calls for downlink frequencies as a function of uplink frequencies such that they are (FRQ modulo 8). Which means my edge device must quickly switch out into chans 0 thru 7 during a listen window.

I wanted to see the sourcecode to ensure that chirpstack is doing that. Thanks.

brocaar · November 28, 2022, 11:17am

For ChirpStack v3, you’ll find this here for US915:

github.com

brocaar/lorawan/blob/master/band/band_us902_928.go#L43


      
          
          func (b *us902Band) GetDefaultMaxUplinkEIRP() float32 {
          	return 30
          }
          
          func (b *us902Band) GetPingSlotFrequency(devAddr lorawan.DevAddr, beaconTime time.Duration) (uint32, error) {
          	downlinkChannel := (int(binary.BigEndian.Uint32(devAddr[:])) + int(beaconTime/(128*time.Second))) % 8
          	// Beaconing is performed on the same channel that normal downstream traffic as
          	// defined in the Class A specification.
          	return b.downlinkChannels[downlinkChannel].Frequency, nil
          }
          
          func (b *us902Band) GetRX1ChannelIndexForUplinkChannelIndex(uplinkChannel int) (int, error) {
          	return uplinkChannel % 8, nil
          }
          
          func (b *us902Band) GetRX1FrequencyForUplinkFrequency(uplinkFrequency uint32) (uint32, error) {
          	uplinkChan, err := b.GetUplinkChannelIndex(uplinkFrequency, true)
          	if err != nil {
          		return 0, err
          	}