Good day,

I am making a wireless sensor network prototype using communication technology, the RFM69HCW module [3]. I use an Arduino nano for the processing unit for the sensor nodes, and for controlling the module with the Arduino, I am using the RadioHead library [4]. For the gateway, I am trying to use a Raspberry. The schematics for the node is the following: Schematic

Note: in the schematics the radio shown is the RFM95W, but as the layout is the exact same as that of the RFM69HCW, I decided to use it and not create a new component. The code I use is the following:

#include <SPI.h>
#include <RHReliableDatagram.h>
#include <RH_RF69.h>
#include <DHT.h>

#define RFM69_FREQ 915.0

#define RFM69_INT 2
#define RFM69_CS 10
#define RFM69_RST 3 // 

#define NODEID 2
#define NETWORKID 69
#define GATEWAY 1

#define LED           9 // LED positive pin
#define GND           8 // LED ground pin

#define DHTPIN 7
#define DHTTYPE DHT22

// Singleton instance of the radio driver
RH_RF69 rf69(RFM69_CS, RFM69_INT);


void Blink(byte PIN, int DELAY_MS);
String getReadings();

void setup() 
  pinMode(RFM69_RST, OUTPUT);
  digitalWrite(RFM69_RST, LOW);


  // Manual reset of rfm
  digitalWrite(RFM69_RST, HIGH);
  digitalWrite(RFM69_RST, LOW);
  if (!rf69.init())
  // Frequency at 915.00 MHz, no encryption.
  // No encryption
  if (!rf69.setFrequency(RFM69_FREQ))
  rf69.setTxPower(20, true);

  // The encryption key has to be the same as the one in the server
  uint8_t syncwords[2];
  syncwords[0] = 0x2d;
  syncwords[1] = NETWORKID;
  rf69.setSyncWords(syncwords, sizeof(syncwords));

  // Init the dht sensor

uint8_t buf[RH_RF69_MAX_MESSAGE_LEN];
uint8_t from;
void loop()
  // Set up a "buffer" for characters that we'll send:
  static char sendBuffer[62];
  static int sendLength = 0;
  bool sendF = false;

  // Get the data from the sensors and send it to the server}
  String data = getReadings();
  uint8_t t = rf69.temperatureRead();
  if (data != '\0')
    data += " " + String(NODEID);
    for (int i = 0; i < data.length(); i++)
      sendBuffer[i] = data[i];
    sendF = true;

  if (sendF)
    if (rf69.send(sendBuffer, sendLength))
      uint8_t len = sizeof(buf);
      if (rf69.recv(buf, &len))

  Blink(LED, 100);
  delay(10000); // 10 seconds

String getReadings()
  float h = dht.readHumidity();
  float t = dht.readTemperature();

  if (isnan(h) || isnan(t)) {
    return String('\0');
  return String(h) + " " + String(t) + " ";

// Blink an LED for a given number of ms
void Blink(byte PIN, int DELAY_MS)

The radio does seem to work with the Arduino. When I call readTemperature() to get the module's temperature, I get a similar value to that of the DHT sensor (with a variation of 0.5 to 1 °C). I first tested it with an Arduino Uno as a gateway, and it did get the data I sent.

Then, I tried to use a Raspberry Pi 3 B with 32-bit Raspbian OS, and I got no data from the sensors. I tried with two different libraries, an adaptation of the RadioHead library to Raspberry [5], and a Python interface [6]. For the connection, I am using the following: Wiring the RFM69 with Raspberry

The code that uses the RadioHead library is:

#include "../RasPiBoards.h"

// Our RFM69 Configuration 
#define RF_FREQUENCY  915.00
#define RF_NODE_ID    1  // Node ID 1 (Gateway)
#define RF_GROUP_ID   69

// Create an instance of a driver

//Flag for Ctrl-C
volatile sig_atomic_t force_exit = false;

void sig_handler(int sig)
  printf("\n%s Break received, exiting!\n", __BASEFILE__);

//Main Function
int main (int argc, const char* argv[] )
  unsigned long led_blink = 0;
  signal(SIGINT, sig_handler);
  printf( "%s\n", __BASEFILE__);

  if (!bcm2835_init()) {
    fprintf( stderr, "%s bcm2835_init() Failed\n\n", __BASEFILE__ );
    return 1;
  printf( "RF69 CS=GPIO%d", RF_CS_PIN);

#ifdef RF_IRQ_PIN
  printf( ", IRQ=GPIO%d", RF_IRQ_PIN );
  // IRQ Pin input/pull down
  pinMode(RF_IRQ_PIN, INPUT);
  bcm2835_gpio_set_pud(RF_IRQ_PIN, BCM2835_GPIO_PUD_DOWN);
  // Now we can enable Rising edge detection
#ifdef RF_RST_PIN
  printf( ", RST=GPIO%d", RF_RST_PIN );
  // Pulse a reset on module
  pinMode(RF_RST_PIN, OUTPUT);
  digitalWrite(RF_RST_PIN, LOW );
  digitalWrite(RF_RST_PIN, HIGH );

  if (!rf69.init()) {
    fprintf( stderr, "\nRF69 module init failed, Please verify wiring/module\n" );
  } else {
    printf( "\nRF69 module seen OK!\r\n");

    // set Network ID (by sync words)
    uint8_t syncwords[2];
    syncwords[0] = 0x2d;
    syncwords[1] = RF_GROUP_ID;
    rf69.setSyncWords(syncwords, sizeof(syncwords));

    // Adjust Frequency
    rf69.setFrequency( RF_FREQUENCY );

    // This is our Node ID
    printf("RF69 GroupID=%d, node #%d init OK @ %3.2fMHz\n", RF_GROUP_ID, RF_NODE_ID, RF_FREQUENCY );


    // listen for incoming message

    printf( " OK NodeID=%d @ %3.2fMHz\n", RF_NODE_ID, RF_FREQUENCY );
    printf( "Listening packet...\n" );

    //Begin the main body of code
    while (!force_exit) {
#ifdef RF_IRQ_PIN
      // Rising edge fired?
      if (bcm2835_gpio_eds(RF_IRQ_PIN)) {
        // Now clear the eds flag by setting it to 1

        if (rf69.available()) {
          uint8_t buf[RH_RF69_MAX_MESSAGE_LEN];
          uint8_t len  = sizeof(buf);
          uint8_t from = rf69.headerFrom();
          uint8_t to   = rf69.headerTo();
          uint8_t id   = rf69.headerId();
          uint8_t flags= rf69.headerFlags();;
          int8_t rssi  = rf69.lastRssi();
          if (rf69.recv(buf, &len)) {
            printf("Packet[%02d] #%d => #%d %ddB: ", len, from, to, rssi);
            printbuffer(buf, len);
          } else {
            Serial.print("receive failed");
#ifdef RF_IRQ_PIN
  printf( "\n%s Ending\n", __BASEFILE__ );
  return 0;

The code using python is the following:

from RFM69 import Radio, FREQ_433MHZ
import datetime
import time

node_id = 2
network_id = 69
recipient_id = 1

with Radio(FREQ_433MHZ, node_id, network_id, isHighPower=True, verbose=True) as radio:
    print ("Starting loop...")
    rx_counter = 0
    tx_counter = 0

    while True:
        if rx_counter > 10:
            rx_counter = 0
            # Process packets
            for packet in radio.get_packets():
                print (packet)

        # Every 5 seconds send a message
        if tx_counter > 5:
            # Send
            print ("Sending")
            if radio.send(2, "TEST", attempts=3, waitTime=100):
                print ("Acknowledgement received")
                print ("No Acknowledgement")
        print("Listening...", len(radio.packets), radio.mode_name)
        delay = 0.5
        rx_counter += delay
        tx_counter += delay

Both codes indicate that the radio is working. When I try to read the radio temperature, the RadioHead library just freezes, and the python code returns a value double that of the Arduino. According to this website [7], it is a problem of power, I tried its solution and still, it did not work.

Can someone please provide me with guidance? I am stuck with this.

[3] https://cdn.sparkfun.com/datasheets/Wireless/General/RFM69HCW-V1.1.pdf

[4] https://github.com/hallard/RadioHead

[5] https://github.com/hallard/RadioHead

[6] https://rpi-rfm69.readthedocs.io/en/latest/index.html

[7] https://stackoverflow.com/questions/51727482/rfm69-radio-transciever-arduino-is-not-registering-acknowledgement-for-transmis

1 Answer 1


I did a similar project with RFM69HCW. Transmitter build with Arduino Pro Mini 8Mhz 3.3V sends a DS18B20 temperature data to a receiver build with Raspberry Pi and python sketch. Transmitter libs, I took from: https://github.com/LowPowerLab/RFM69. For the receiver I used the libs from: https://github.com/etrombly/RFM69, which is a port from the LowPowerLab to python for raspberry pi. Have a look at this! By the way: In your arduino code you definde a frequency of 915MHz. You should use the same frequeny in your Python sketch!

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