Lopy 4 433 output power



  • Hello,
    What is the real maximum output power that can be achieve with the Lopy 4.
    The datasheet seems to say +17 dBm or +20 dBm in boost mode, but we measure a maximum -14 dBm on several boards with no change when boost is activated.



  • Here is a minimal example that show the problem.
    Expansion board V3.1 + Lopy4
    Platform IO / C++

    #include <SPI.h>
    #include <LoRa.h>
    
    int counter = 0;
    
    #define LORA_SCK          5    // GPIO5  -- SX1278's SCK
    #define LORA_MISO         19   // GPIO19 -- SX1278's MISO
    #define LORA_MOSI         27   // GPIO27 -- SX1278's MOSI
    #define LORA_SS           18   // GPIO18 -- SX1278's CS
    #define LORA_RST          23   // GPIO14 -- SX1278's RESET
    #define LORA_DI0          26   // GPIO26 -- SX1278's IRQ(Interrupt Request)
    //#define LORA_DI0          33   // GPIO26 -- SX1278's IRQ(Interrupt Request)
    #define LORA_FREQ_BAND    433E6
    
    void setup() {
      Serial.begin(115200);
      while (!Serial);
    
      Serial.println("Init LoRa Sender");
      SPI.begin(LORA_SCK, LORA_MISO, LORA_MOSI, LORA_SS);
      LoRa.setPins(LORA_SS, LORA_RST, LORA_DI0);
    
      if (!LoRa.begin(LORA_FREQ_BAND)) {
        Serial.println("Starting LoRa failed!");
        while (1);
      }
    
      // set spread factor
      LoRa.setSpreadingFactor(8);  // defaults to 7, supported values are between 6 and 12
      LoRa.setTxPower(17); // TX power in dB, defaults to 17 - value from 2 to 20
      LoRa.setSignalBandwidth(125E3); // defaults to 125E3. Supported values are 7.8E3, 10.4E3, 15.6E3, 20.8E3, 31.25E3, 41.7E3, 62.5E3, 125E3, and 250E3
      // LoRa.setCodingRate4(codingRateDenominator); // defaults to 5, Supported values are between 5 and 8, these correspond to coding rates of 4/5 and 4/8. The coding rate numerator is fixed at 4.
      // LoRa.enableCrc(); // LoRa.disableCrc(); // by default a CRC is not used.
    }
    
    void loop() {
      Serial.print("Sending packet: ");
      Serial.println(counter);
    
      Serial.println("start to send packet ... ");
      // send packet
      LoRa.beginPacket();
      LoRa.print(millis());
      LoRa.print(" ");
      LoRa.print(counter);
      LoRa.print(" abcdefghijklmnopqrstuvwxyz");
      LoRa.endPacket();
    
      delay(1000);
      Serial.print("packet sent... ");
      counter++;
    
    }
    
    

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