Can not receive downlink message from RAK7248

[bienxanh1901]

Hi every one,
I am facing to the downlink issue on RAK7248.
I have written a simple program in RAK7248 to send message (ie ping message) periodically. The tx_ptk is as following and lgw_send return success.

    m_txPingPkt.freq_hz = 922200000;
    m_txPingPkt.tx_mode = IMMEDIATE;
    m_txPingPkt.count_us = 0;
    m_txPingPkt.rf_chain = 0;
    m_txPingPkt.rf_power = 20; // dBm
    m_txPingPkt.modulation = MOD_LORA;
    m_txPingPkt.freq_offset = 0;
    m_txPingPkt.bandwidth = BW_125KHZ;
    m_txPingPkt.datarate = DR_LORA_SF7;
    m_txPingPkt.coderate = CR_LORA_4_5;
    m_txPingPkt.invert_pol = true;
    m_txPingPkt.f_dev = 0;
    m_txPingPkt.preamble = 8;
    m_txPingPkt.no_crc = true;
    m_txPingPkt.no_header = true;
    m_txPingPkt.size = sizeof(message_t);
    memcpy(m_txPingPkt.payload, &pingMsg, m_txPingPkt.size);

    while (true)
    {
        // send ping message
        {        
            std::lock_guard<std::mutex> lck(m_mux);
            if (lgw_send(&m_txPingPkt) == LGW_HAL_ERROR)
            {
                Logger::log()->error("Error send message");
            }
        }

        std::this_thread::sleep_for(std::chrono::milliseconds(delay_ms));
    }

In end device side, I use Lora_E5_mini to receive the message on same frequency. But it did not receive any message.
I am wonder if i am wrong in tx configuration? In RAK7248, I can receive uplink message from Lora_E5_mini.

Does anyone have same issue or can help me in this case?

Thank you very much!
Hai Pham

[mcoracin]

Hello,
One thing that could be wrong, depending on how the end-device is configured to receive, is that you have set "no_header" to true. This means that you are sending a LoRa packet without header (IMPLICIT HEADER), so the end-device has to be configured accordingly.
If it is not intentional, you should set no_header to false.
Best regards,
Michael