gistfile1.c

#include <SPI.h>
#include <Ethernet.h>
#include <SD.h>
#include <SoftwareSerial.h>
#include <Adafruit_Thermal.h>

byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
const char host[] = "192.168.1.100";
char cacheFilename[] = "TMP";

const byte printer_RX_Pin = 8; // this is the green wire
const byte printer_TX_Pin = 9; // this is the yellow wire
const byte SD_Pin = 4;         // the SD Card SPI pin

bool downloadWaiting = false;
bool statusOk = false;
unsigned long content_length = 0;

EthernetClient client;
Adafruit_Thermal printer(printer_RX_Pin, printer_TX_Pin);


void die(unsigned int times) {
  while(true);
}


void checkForDownload() {

  Serial.print("checkForDownload ");
  Serial.println(millis());

  content_length = 0;
  statusOk = false;
  unsigned long length = 0;

  if (SD.exists(cacheFilename)) {
    if (!SD.remove(cacheFilename)) {
      die(4);
    }
  }
  File cache = SD.open(cacheFilename, FILE_WRITE);

  if(client.connect(host, 80)) {

    client.println("GET /printer.php HTTP/1.1");
    client.print("Host: "); client.println(host);
    client.println("User-Agent: arduino-ethernet");
    client.println("Connection: close");
    client.println();

    bool parsingHeader = true;

    while(client.connected()) {
      while(client.available()) {

        if (parsingHeader) {

          client.find((char*)"HTTP/1.1 ");
          char statusCode[] = "000";
          client.readBytes(statusCode, 3);
          statusOk = (strcmp(statusCode, "200") == 0);

          client.find((char*)"Content-Length: ");
          char c;
          while (isdigit(c = client.read())) {
            content_length = (content_length * 10) + (c - '0');
          }

          client.find((char*)"\n\r\n");
          parsingHeader = false;

        } else {
          if(length < content_length) {
            cache.write((byte)client.read());
            length++;
          } else {
            client.read();
          }
        }

      }
    }

    client.stop();
    cache.seek(0);

    if (statusOk && content_length > 0 && (content_length == length) && (content_length == cache.size())) {
      downloadWaiting = true;
    }

  } else {
    client.stop();
  }

  cache.close();

}


void printFromDownload() {

  Serial.println("printFromDownload");

  File cache = SD.open(cacheFilename);
  byte b;

  while (content_length--) {
    printer.write((byte)cache.read());
  }

  printer.feed();

  cache.close();
  downloadWaiting = false;

}


void setup(){

  Serial.begin(9600);
  while (!Serial) {
    ;
  }
  delay(1000);
  Serial.println("Init");

  Serial.println("Connect SD");
  pinMode(SD_Pin, OUTPUT);
  if (!SD.begin(SD_Pin)) {
    Serial.println("SD Error");
    die(2);
  }

  Serial.println("Connect Ethernet");
  if (Ethernet.begin(mac) == 0) {
    Serial.println("Ethernet Error");
    die(3);
  }

  Serial.println("Connect Printer");
  printer.begin(255);

  delay(1000);

}


void loop() {
  if (downloadWaiting) {
    printFromDownload();
    delay(5000);
  } else {
    checkForDownload();
    if (!downloadWaiting) {
      delay(10000);
    }
  }
}