RFM69 RSSI value report

[jpaulin]

@rmtucker In my RFM69 sensors using ver2.1 I'm doing as follows to check RSSI and, as well, how to check the background noise level. I have them implemented as two sensor values being reported every 5 minutes in the loop() to the gateway and controller.

void loop()      
{
  float humidity = dht.readHumidity();       // get dht22 humidity
  if (isnan(humidity)) {
    Serial.println("Failed reading humidity from DHT");
  } else {
    send(msgHum.set(humidity, 1));           // send dht22 humidity
  }

  float temperature = dht.readTemperature(); // get dht22 temperature
  if (isnan(temperature)) {
    Serial.println("Failed reading temperature from DHT");
  } else {
    send(msgTemp.set(temperature, 1));       // send dht22 temperature
  }
  digitalWrite(DHT22_PWR,LOW);               // save some power. Turn off dht22 module.
  
  rssi = _radio.readRSSI();                  // read RSSI in RFM69. Measure reception signal level from gw
  send(msgRSSI1.set(rssi));                  // send RSSI, signal level to gateway

  wait(500);                                 // wait to get idle
  rssi = _radio.readRSSI();                  // read RSSI in RFM69. Measure background noise
  send(msgRSSI2.set(rssi));                  // send RSSI, noise level to gateway
  
  sleep(SLEEP_TIME);                         // sleep a bit
  digitalWrite(DHT22_PWR,HIGH);              // wake up dht22 module
  wait(2000);                                // warm up dht22 module
}

To get the RSSI value it's read in the sketch ( int rssi = _radio.readRSSI(); ) immediately after sending something, in this case the dht22 temperature. To check the background noise the RSSI level is read again 500ms after being kept idle (probably a shorter waiting period would work as well, but haven't studied it as it's not a critical issue for me). Normally the background noise-floor should be something around -95dBm and -115dBm. If you have some external interference, it could be easily detected with this method.

[rmtucker]

@jpaulin
Thank you so much for the info that rssi can be extracted in V2.1.0.
Would you be able to post your full sketch as it would be easier for me to extract the bits i need.?
I just can not understand why before your answer i was being told it is not possible in V2.1.0 to do this?
Or does this need another version of the Rfm69 library?

[jpaulin]

@rmtucker Here's the complete sketch. It's a DHT22 temp/humidity battery powered sensor node with an RFM69 radio.

/**
 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 *
 * Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
 * Copyright (C) 2013-2015 Sensnology AB
 * Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
 *
 * Documentation: http://www.mysensors.org
 * Support Forum: http://forum.mysensors.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 *******************************
 *
 * REVISION HISTORY
 * Version 1.0 - Henrik EKblad
 * 
 * DESCRIPTION
 * This sketch provides an example how to implement a humidity/temperature
 * sensor using DHT11/DHT-22 
 * http://www.mysensors.org/build/humidity
 */

// Enable debug prints
#define MY_DEBUG

// Enable and select radio type attached
//#define MY_RADIO_NRF24
#define MY_RADIO_RFM69

#define MY_RFM69_FREQUENCY   RF69_433MHZ

#define MY_NODE_ID 13                        // Identity for temp/hum sensor

// Set blinking period
#define MY_DEFAULT_LED_BLINK_PERIOD 50

// Flash leds on rx/tx/err
//#define MY_DEFAULT_ERR_LED_PIN 7           // Error led pin  red
//#define MY_DEFAULT_RX_LED_PIN  6           // Receive led pin  yellow
#define MY_DEFAULT_TX_LED_PIN  9             // Transmit led pin  green

#define MY_WITH_LEDS_BLINKING_INVERSE

const byte BATT_ADC = 1;                     // ADC Pin to measure battery level

#include <MySensors.h>
#include <DHT.h>


unsigned long SLEEP_TIME = 300000;           // Sleep time between reads (in milliseconds)



#define CHILD_ID_HUM 0
#define CHILD_ID_TEMP 1
#define DHTPIN 18                            // Input pin from DHT22
#define DHT22_PWR 6                          // Vdc pin DHT22 to get it to sleep
#define DHTTYPE DHT22

DHT dht(DHTPIN, DHTTYPE);


#define CHILD_ID_RSSI_HIGH  7                // RSSI received signal level
#define CHILD_ID_RSSI_LOW   8                // RSSI background noise level
#define CHILD_ID_TEMP2      9                // internal temperature RFM69 chip

int rssi;                                    // RSSI RFM69 chip
int temp2;                                   // Internal temperature RFM69 chip

int batteryLevel;                            // measured battery level
int batteryPcnt;                             // measured battery level in percentage

MyMessage msgHum(CHILD_ID_HUM, V_HUM);
MyMessage msgTemp(CHILD_ID_TEMP, V_TEMP);

MyMessage msgRSSI1(CHILD_ID_RSSI_HIGH, V_VAR1);
MyMessage msgRSSI2(CHILD_ID_RSSI_LOW, V_VAR1);
MyMessage msgTemp2(CHILD_ID_TEMP2, V_TEMP);


void setup()  
{ 
  pinMode(DHT22_PWR,OUTPUT);
  digitalWrite(DHT22_PWR,HIGH);              // power-on dht22
  wait(2000);

  dht.begin();                               // Start-up DHT22 sensor Temperature/Humidity
}

void presentation() 
{
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("Temp_Hum", "1.0");

  // Register all sensors to gw (they will be created as child devices)
  present(CHILD_ID_HUM, S_HUM);
  present(CHILD_ID_TEMP, S_TEMP);

  present(CHILD_ID_RSSI_HIGH, S_CUSTOM);
  present(CHILD_ID_RSSI_LOW, S_CUSTOM);
  present(CHILD_ID_TEMP2, S_TEMP);
}

void loop()      
{
  float humidity = dht.readHumidity();       // get dht22 humidity
  if (isnan(humidity)) {
    Serial.println("Failed reading humidity from DHT");
  } else {
    send(msgHum.set(humidity, 1));           // send dht22 humidity
    wait(200);
  }

  float temperature = dht.readTemperature(); // get dht22 temperature
  if (isnan(temperature)) {
    Serial.println("Failed reading temperature from DHT");
  } else {
    send(msgTemp.set(temperature, 1));       // send dht22 temperature
  }
  digitalWrite(DHT22_PWR,LOW);               // save some power
  
  rssi = _radio.readRSSI();                  // read RSSI in RFM69. Measure reception signal from gw
  send(msgRSSI1.set(rssi));                  // send RSSI level
  wait(500);                                 // wait to get idle
  
  rssi = _radio.readRSSI();                  // read RSSI in RFM69. Wait and measure background noise
  send(msgRSSI2.set(rssi));                  // send RSSI level
  wait(200);                                 // wait for next send
  
  temp2 = _radio.readTemperature(1);         // read temperature in RFM69
  send(msgTemp2.set(temp2));                 // send temperature

  batteryLevel = analogRead(BATT_ADC);       //  (* 0.0032225806)
  batteryPcnt = batteryLevel / 10;           // battery percentage
  
  sendBatteryLevel(batteryPcnt);             // send battery level in percentage to controller

  // if (oldBatteryPcnt != batteryPcnt) {    // use if not to send every cycle
  //     sendBatteryLevel(batteryPcnt);
  //     oldBatteryPcnt = batteryPcnt;
  // }

  
  sleep(SLEEP_TIME);                         // sleep a bit
  digitalWrite(DHT22_PWR,HIGH);              // wake up DHT sensor
  wait(2000);                                // warm up DHT sensor
}

void receive(const MyMessage &message) {
  // We only expect one type of message from controller. But we better check anyway.
  Serial.println("something came in");
  
  if (message.type==V_VAR1) {                // reception to change SLEEP_TIME.
     SLEEP_TIME = message.getULong();        // send topic: eg. my_RFM69_gw1-in/3/1/1/0/24 30000 (payload in ms)
   }                                         // MQTT_publish_topic_prefix/Node_Id/Sensor_Id/Cmd_Type/Ack_flag/type(V_VAR1=24) payload
}

readRSSI(); is an internal function in the RFM69.h / RFM69.cpp library that I'm calling in the sketch to get the RSSI and background noise level.

[jpaulin]

@rmtucker Another feature I'm using in the sketch, by calling directly the RFM69 library, is reading the temperature sensor in the RFM69.

temp2 = _radio.readTemperature(1);         // read temperature in RFM69

The value (1) sent in the call above to the RFM69 library is a calibration in Centigrades (e.g. 1 = +1 °C). Added here to show the possibility to adjust the measured temperature. The temperature sensor on the chip is not as accurate as for example a dht22 and needs sometimes some manual adjustment.

[mihai.aldea]

The onboard temperature sensor is not a cool freebie. It's meant to be a way to check the approximate environmental temperature for the outdoor or industrial devices (not only sensor nodes) using RFM69.

[rmtucker]

@jpaulin
Just wanted to thank you for taking the time to post your example for rssi.
I have just finished putting my new rfm69 gateway together and about to start assembling a new node to try everything out.
I will let you know how i get on.

[gieemek]

In the 2.2 version of MySensors (development branch) the new driver for RFM69 is built. It has new command for reading RSSI value: RFM69_getSendingRSSI() and RFM69_getReceivingRSSI(), so now is very easy to get RSSI value.
You can get some more information from ATC Signal Report which are useful - look at RFM69_RFM95_ATC_SignalReport example.

[gieemek]

This post is deleted!

[gohan]

@gieemek

what kind of variable and type are better for reporting RSSI?

[gieemek]

@gohan I use V_VAR1 type of variable.

[gohan]

@gieemek ok, but how about when you present the child? S_CUSTOM is not accepted by Domoticz S_SOUND could be an option

[napo7]

I see in the domoticz code that there are some fields to record Signal Level for other sensors types.
Making domoticz handle the signal level would then be possible.
There is 2 enhancements to do so :

• Handle a standard variable or subtype in MySensors to carry the signal or RSSI level (github issue 581 : https://github.com/mysensors/MySensors/issues/581)
• Modify the domoticz code to show somewhere the Signal Level for MySensors devices. (no github issue yet)

That would be interresting, since it would also allow to trigger some custom scripts if a device falls in a poor level...

[gieemek]

I do not know Domotich - I am working with openHAB through MQTT protocol, which simply reads the sent value of variable and does not wonder what type they are. Yes, I use S_CUSTOM variable to send RSSI value.
But it really doesn't matter what kind of variable you use. The variable type tells to MySensors that its value is for example: light level, temperature, or voltage, but you can send a temperature value using the S_POWER variable - no problem with that.
RSSI should be expressed as an integer, so what is realy important that you choose the variable type declared as integer value, such as i.e. S_LIGHT_LEVEL.
Once you have that value in the controller (openHAB), you can do whatever you want with it.
So it is in openHAB, and I hope in Domoticz the same.

[gohan]

I used S_SOUND so it will report it as 'db', so for now I am happy with it.

[zboblamont]

@jpaulin I can see the value of obtaining Gateway RSSI for individual battery powered nodes to inform programmed power settings on them in the absence of ATC implementation at the Node itself, but not sure I understand the purpose of RSSI readings at the node other than to establish noise thresholds on the Gateway signal.

Although the function of the Gateway is to forward messages to the Controller, is it possible for the Gateway to read and forward RSSI readings for nodes as if locally attached sensors?

[gohan]

Reading rssi and power on the node it gives you an idea of how much signal that node is getting and if there are interferences around it

[zboblamont]

@gohan Yes, I understood that aspect. I can imagine certain environments where the SNR might inform change of Node location or shielding or directivity of antenna, or increased output from the Gateway, but I would have thought that a one-off task unless the node noise background changes frequently...

[gohan]

You can always put a counter to send rssi reports after X amount of other data being sent

[zboblamont]

@gohan True, but if no change to the environment is anticipated, why use battery power to convey it at all?
My own interest in what RSSI the Gateway is receiving should also be a one-time exercise, but is more difficult to implement I suppose.

Until such time the 2.2 version is released, and what it provides becomes clearer, I might just do the checking with two portable nodes...

[gohan]

I can show you how background noise rssi and power output changes during the day and I'm not moving things around