Downlink data ：max_payload_size

ChirpStack Application Server
1

DR=5:

  • item_size:“55”
  • max_payload_size:“51”
  • queue_item_id:“53aa1833-e210-4802-9a2e-0fc490f1f4cf”
    Why do I get DR=5, the maximum load is still 51, shouldn’t it be 222

This is what I have to configure：
LoRaWAN 1.0.2 A
Default ADR

2

On Chripstack v4, the source code is here for your region: chirpstack/cn470.rs at e2214f94857bf3bfdbb8a981131a3eb9ccb8c5d5 · chirpstack/chirpstack · GitHub (n is for DL size)

See:

MacVersion::LORAWAN_1_0_2,
    [(
        Revision::Latest, // A & B
        [
            (0, MaxPayloadSize { m: 59, n: 51 }),
            (1, MaxPayloadSize { m: 59, n: 51 }),
            (2, MaxPayloadSize { m: 59, n: 51 }),
            (3, MaxPayloadSize { m: 123, n: 115 }),
            (4, MaxPayloadSize { m: 230, n: 222 }),
            (5, MaxPayloadSize { m: 230, n: 222 }),
        ]

But if ADR is active, maybe your device switched to DR0…

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