HTTP JSON API: ENC28J60 + DHT11 + BMP180 + UNO

DHT11_BMP180_server.ino

// HTTP JSON API.
 
#include <EtherCard.h>

#include <DHT.h>

#include <Wire.h>
#include <Adafruit_BMP085_U.h>

// Ethernet:

// TCP/IP send/recv buffer:
byte Ethernet::buffer[512];

// Ethernet MAC address - must be unique on the network!
static byte myMAC[] = { 0x74, 0x69, 0x69, 0x2D, 0x30, 0x31 };

const char s200[] PROGMEM = "HTTP/1.0 200 OK\r\n";
const char s503[] PROGMEM = "HTTP/1.0 503 Service Unavailable\r\n";

const char headers[] PROGMEM = "Server: Arduino Uno\r\n"
                               "Content-Type: application/json\r\n"
                               "\r\n";

const char b503[] PROGMEM = "{\"error\":\"service_unavailable\"}";

// DHT11 Sensor:

#define DHTPIN  2
#define DHTTYPE DHT11

DHT dht(DHTPIN, DHTTYPE);

// BMP180 Sensor:

bool bmp_error;
Adafruit_BMP085_Unified bmp = Adafruit_BMP085_Unified(10180);

void setup(){
  if (!ether.begin(sizeof Ethernet::buffer, myMAC)) {
    // OOPS, failed to initialise the ethernet board!
    while(1);
  }
  if(!bmp.begin()) {
    // OOPS, failed to initialiset he BMP180 sensor!
    bmp_error = true;
  }
  ether.dhcpSetup();
}

void loop(){
  // BMP180:
  sensors_event_t event;
  bmp.getEvent(&event);

  // DHT11:
  float humd = dht.readHumidity();
  float temp = dht.readTemperature();

  // Wait for an incoming TCP packet, but ignore its contents.
  if (!ether.packetLoop(ether.packetReceive())) {
    return;
  }

  // Check that all values are ready:
  if (isnan(humd) || isnan(temp) || !(humd || temp) || !event.pressure) {
    error_503();
    return;
  }

  // Construct a response:
  char body[4096];
  int pos;

  pos += sprintf(body+pos, "%s", "{\"BMP180\":{\"pressure\":");
  pos += sprintf(body+pos, "%s", dtostrf(event.pressure, 0, 2, body+pos));
  pos += sprintf(body+pos, "%s", "},\"DHT11\":{\"humidity\":");
  pos += sprintf(body+pos, "%s", dtostrf(humd, 0, 2, body+pos));
  pos += sprintf(body+pos, "%s", ",\"temperature\":");
  pos += sprintf(body+pos, "%s", dtostrf(temp, 0, 2, body+pos));
  pos += sprintf(body+pos, "%s", "}}");

  respond(body, ++pos);
}

void respond(char *body, int size) {
  unsigned int offset;
  memcpy_P(ether.tcpOffset() + offset, s200,    sizeof s200);    offset += sizeof s200 - 1;
  memcpy_P(ether.tcpOffset() + offset, headers, sizeof headers); offset += sizeof headers - 1;
  memcpy  (ether.tcpOffset() + offset, body,    size);           offset += size - 1;
  ether.httpServerReply(offset);
}

void error_503() {
  unsigned int offset;
  memcpy_P(ether.tcpOffset() + offset, s503,    sizeof s503);    offset += sizeof s503 - 1;
  memcpy_P(ether.tcpOffset() + offset, headers, sizeof headers); offset += sizeof headers - 1;
  memcpy_P(ether.tcpOffset() + offset, b503,    sizeof b503);    offset += sizeof b503 - 1;
  ether.httpServerReply(offset);
}