RFM95 with arduino uno Transmitter and receiver

Before starting to  test communicate with Rfm95 with Arduino uno download radio head library

radio head library for arduino uno with rfm
https://drive.google.com/open?id=1iBQWCOm13X3bdDKEcy0czGebPDz_PqQ-

RFM95 with arduino uno connections:

ARDUINO UNO	RFM 95
Gnd	Gnd
3.3v	3.3v
D5	reset
D2	DIO 0
D3	DIO1
D13(SCK)	SCK
D12(MISO)	MISO
D11(MOSI)	MOSI
D10(SS)	NSS

NOTE:

LEVEL SHIFTER FOR BETTER OUTPUT




sender side code:

#include <SPI.h>
#include <RH_RF95.h>

RH_RF95 rf95;

int led = 9;

void setup()
{
  pinMode(led, OUTPUT);   
  Serial.begin(9600);
  while (!Serial) ; // Wait for serial port to be available
  if (!rf95.init())
    Serial.println("init failed");

}

void loop()
{
  if (rf95.available())
  {
    // Should be a message for us now 
    uint8_t buf[RH_RF95_MAX_MESSAGE_LEN];
    uint8_t len = sizeof(buf);
    if (rf95.recv(buf, &len))
    {
      digitalWrite(led, HIGH);
     // RH_RF95::printBuffer("request: ", buf, len);
      Serial.print("got request: ");
      Serial.println((char*)buf);
   
//      Serial.print("RSSI: ");
//      Serial.println(rf95.lastRssi(), DEC);
   
   
      /***************************************/
      // Send a reply
      /***************************************/
    char data[32]="";
   int availableBytes = Serial.available();
   for(int i=0; i<availableBytes; i++)
    {   
        data[i]=Serial.read();
    }
      rf95.send(data, sizeof(data));
      rf95.waitPacketSent();
      Serial.println("Sent::");
      Serial.print(data);
       digitalWrite(led, LOW);
     
    }
    else
    {
      Serial.println("recv failed");
    }
  }
  delay(100);
}


receiver side code:

// rf95_client.pde

#include <SPI.h>
#include <RH_RF95.h>

int led = 9;

RH_RF95 rf95;


void setup()
{
  pinMode(led, OUTPUT); 

  Serial.begin(9600);
  while (!Serial) ; // Wait for serial port to be available
  if (!rf95.init())
    Serial.println("init failed");
}

void loop()
{
  rfm95_uart();

}

void rfm95_uart()
{
  Serial.println("Sending to rf95_server::");


  char data[32]="";
   int availableBytes = Serial.available();
   for(int i=0; i<availableBytes; i++)
    {   
        data[i]=Serial.read();
    }
      rf95.send(data, sizeof(data));
      rf95.waitPacketSent();
      Serial.println("Sent::");
      Serial.print(data);
       digitalWrite(led, LOW);

  uint8_t buf[RH_RF95_MAX_MESSAGE_LEN];
  uint8_t len = sizeof(buf);


  if (rf95.waitAvailableTimeout(3000))
  {
    // Should be a reply message for us now 
    if (rf95.recv(buf, &len))
   {
      Serial.print("got reply: ");
      Serial.println((char*)buf);
//      Serial.print("RSSI: ");
//      Serial.println(rf95.lastRssi(), DEC); 
    }

    else
    {
      Serial.println("recv failed");
    }
  }

  else
  {
    Serial.println("No reply, is rf95_server running?");
  }
  delay(400);


  }
out put:

after some modification::
send code:
#include <SPI.h>
#include <RH_RF95.h>

RH_RF95 rf95;

int led = 9;

void setup()
{
  pinMode(led, OUTPUT);   
  Serial.begin(9600);
  while (!Serial) ; // Wait for serial port to be available
  if (!rf95.init())
    Serial.println("init failed");
}

void loop()
{
  if (rf95.available())
  {
    // Should be a message for us now 
    uint8_t buf[RH_RF95_MAX_MESSAGE_LEN];
    uint8_t len = sizeof(buf);
    if (rf95.recv(buf, &len))
    {
      digitalWrite(led, HIGH);
     // RH_RF95::printBuffer("request: ", buf, len);
      Serial.print("got request: ");
      Serial.println((char*)buf);
      /***************************************/
      // Send a reply
      /***************************************/
    char data[32]="";
   int availableBytes = Serial.available();
   for(int i=0; i<availableBytes; i++)
    {   
        data[i]=Serial.read();
    }
      rf95.send(data, sizeof(data));
      rf95.waitPacketSent();
      Serial.println("Sent::");
      Serial.print(data);
       digitalWrite(led, LOW);
    }
    else
    {
      Serial.println("recv failed");
    }
  }
  delay(100);

}

Receiver code:
// rf95_client.pde

#include <SPI.h>
#include <RH_RF95.h>

int led = 9;

RH_RF95 rf95;


void setup()
{
  pinMode(led, OUTPUT); 

  Serial.begin(9600);
  while (!Serial) ; // Wait for serial port to be available
  if (!rf95.init())
    Serial.println("init failed");
}

void loop()
{
  rfm95_uart();

}

void rfm95_uart()
{
  //Serial.println("Sending to rf95_server::");
  char data[32]="";
   int availableBytes = Serial.available();
   for(int i=0; i<availableBytes; i++)
    {   
        data[i]=Serial.read();
    }
      rf95.send(data, sizeof(data));
      rf95.waitPacketSent();
      Serial.println("Sent::");
      Serial.print(data);
       digitalWrite(led, LOW);

  uint8_t buf[RH_RF95_MAX_MESSAGE_LEN];
  uint8_t len = sizeof(buf);
  if (rf95.waitAvailableTimeout(3000))
  {
    if (rf95.recv(buf, &len))
   {
      Serial.print("got reply: ");
      Serial.println((char*)buf);
    }

    else
    {
      Serial.println("recv failed");
    }
  }
  else
  {
    Serial.println("No reply, is rf95_server running?");
  }
  delay(400);
  }

Node MCU with WIFI scanning

/*
    This sketch demonstrates how to scan WiFi networks.
    The API is almost the same as with the WiFi Shield library,
    the most obvious difference being the different file you need to include:
*/
#include "ESP8266WiFi.h"

void setup() {
  Serial.begin(115200);

  // Set WiFi to station mode and disconnect from an AP if it was previously connected
  WiFi.mode(WIFI_STA);
  WiFi.disconnect();
  delay(100);

  Serial.println("Setup done");
}

void loop() {
  Serial.println("scan start");

  // WiFi.scanNetworks will return the number of networks found
  int n = WiFi.scanNetworks();
  Serial.println("scan done");
  if (n == 0) {
    Serial.println("no networks found");
  } else {
    Serial.print(n);
    Serial.println(" networks found");
    for (int i = 0; i < n; ++i) {
      // Print SSID and RSSI for each network found
      Serial.print(i + 1);
      Serial.print(": ");
      Serial.print(WiFi.SSID(i));
      Serial.print(" (");
      Serial.print(WiFi.RSSI(i));
      Serial.print(")");
      Serial.println((WiFi.encryptionType(i) == ENC_TYPE_NONE) ? " " : "*");
      delay(10);
    }
  }
  Serial.println("");

  // Wait a bit before scanning again
  delay(5000);
}

output:

SHT31 Temparature and Humidity sensor with arduino uno

#include <Arduino.h>
#include <Wire.h>
#include "Adafruit_SHT31.h"

Adafruit_SHT31 sht31 = Adafruit_SHT31();

void setup() {
  Serial.begin(9600);

  while (!Serial)
    delay(10);     // will pause Zero, Leonardo, etc until serial console opens

  Serial.println("SHT31 test");
  if (! sht31.begin(0x44)) {   // Set to 0x45 for alternate i2c addr
    Serial.println("Couldn't find SHT31");
    while (1) delay(1);
  }
}


void loop() {
  float t = sht31.readTemperature();
  float h = sht31.readHumidity();

  if (! isnan(t)) {  // check if 'is not a number'
    Serial.print("Temp *C = "); Serial.println(t);
  } else {
    Serial.println("Failed to read temperature");
  }
 
  if (! isnan(h)) {  // check if 'is not a number'
    Serial.print("Hum. % = "); Serial.println(h);
  } else {
    Serial.println("Failed to read humidity");
  }
  Serial.println();
  delay(1000);
}

output::

c interview question25

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int x=55, y=17;
    printf("%d\n",func(x,y));
    return 0;
}
func (int x, int y)
{
    int q=0;
    if (x<y)
        return 0;
    else
        return func(x-y,y)+1;
}

output::

3

c interview question24

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int a=7,b=8;
    printf("%d\n",fune(a,b)) ;
    return 0;
}

fune(int x,int y)
{
    if (x==0)
        return y;
    else
        fune(--x, ++y);
}

output::

15

c interview question 23

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int a=2,b=6;
    printf("%d\t",funcl(a,b));
    printf("%d\n",func2(a,b));
    return 0;
}
funcl(int a, int b)
{
    int i,s=0;
    for(i=a;i<=b;i++)
    {s=s+i*i;}
return s;
}
func2(int a, int b)
{
    int s;
    if (a<b)
        s=a*a+func2(a+1,b);
    else
        s=a*a;
}

output::

90      90

c interview question 22

#include <stdio.h>
#include <stdlib.h>

int main()
{
   int n=8;
    printf("%d\n",func(n));
    return 0;
}



func(int n)
{
    if(n==0)
        return 0;
    else
        return(n+func(n-1));
}

output::
36

c interview question 21

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int i=0,k=3;
    i+=func(k);
    i+=func(k);
    i+=func(k);
    printf("%d\n",i);
    return 0;
}

func(int k)
{
    static int m=2;
    m=m+k;
    return m;
}

output::

24

explanation:

1st->k=3,m=5,i=5

2nd->k=3,m=8,i=13

3rd->k=3,m=11,i=24

c interview question20

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int a=2,b=5;
    a=func(a+b,a-b);
    printf("%d\n",a);
    return 0;
}

func (int x, int y)
{ return x+y, x-y;}

output::
10

c interview questions 19

#include <stdio.h>
#include <stdlib.h>


int a=5;
void func(void );

int main()
{
    func() ;
    printf ("%d\n", a);
    return 0;
}

void func (void)
{
int a=2;
printf ("%d\t", a);
}

output::
2       5

c interview questions18

#include <stdio.h>
#include <stdlib.h>

void func (int a, int b);
int main()
{
    int i=5,j=10;
    func(i/2,j%3) ;

    return 0;
}
void func(int a,int b)
{
    a=a/2;
    b--;
    printf("%d\t",a+b) ;
}

output::
1