Sending binary commands from PHP to Arduino powered thermal printer - php

Question

I am having some fun playing around with an Arduino (Uno rev 3) and a thermal printer (this model https://www.sparkfun.com/products/10438). The Arduino makes a request every 10 seconds to my local machine (via an Ethernet shield) and stores the response (if 200) on an SD card. It then prints this out using this library https://github.com/adafruit/Adafruit-Thermal-Printer-Library .
So far I have it correctly polling, storing and printing basic text but now I'm trying to use some of the more advanced commands (underline, inverse etc). My ultimate goal is to send images down and handle all of the rendering on the server ala http://printer.gofreerange.com/ .
The problem is that the commands I am sending are been outputted as text characters. Some commands work (line feed), but others are garbled. I have attached both the Arduino code and the basic PHP script it is calling. Any help?
Arduino:
#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.println("checkForDownload");
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(){
pinMode(SD_Pin, OUTPUT);
if (!SD.begin(SD_Pin)) {
die(2);
}
if (Ethernet.begin(mac) == 0) {
die(3);
}
Serial.begin(9600);
printer.begin(255);
delay(1000);
}
void loop() {
if (downloadWaiting) {
printFromDownload();
delay(5000);
} else {
checkForDownload();
if (!downloadWaiting) {
delay(10000);
}
}
}
PHP:
<?php
ob_start();
// Turn on Inverse mode
// Doesn't work
echo pack('S', 29);
echo pack('S', 66);
echo pack('S', 1);
$string = 'Testing 1, 2, 3';
foreach(str_split($string) as $char) {
echo pack('S', ord($char)); // works
}
// Turn off Inverse mode
echo pack('S', 29);
echo pack('S', 66);
echo pack('S', 0);
// Line feed
echo pack('S', 10); // works
$content = ob_get_clean();
$length = strlen($content);
header("Content-Length: $length");
echo $content;

Answer 1

It seems that you can't print bitmap data directly with printer.write(). The printer expects some special bytes to turn on bitmap printing mode as you can see in the printBitmap() method. (writeBytes(18, 42, chunkHeight, rowBytesClipped))
void Adafruit_Thermal::printBitmap(
int w, int h, const uint8_t *bitmap, bool fromProgMem) {
int rowBytes, rowBytesClipped, rowStart, chunkHeight, x, y, i;
rowBytes = (w + 7) / 8; // Round up to next byte boundary
rowBytesClipped = (rowBytes >= 48) ? 48 : rowBytes; // 384 pixels max width
for(i=rowStart=0; rowStart < h; rowStart += 255) {
// Issue up to 255 rows at a time:
chunkHeight = h - rowStart;
if(chunkHeight > 255) chunkHeight = 255;
writeBytes(18, 42, chunkHeight, rowBytesClipped);
for(y=0; y < chunkHeight; y++) {
for(x=0; x < rowBytesClipped; x++, i++) {
PRINTER_PRINT(fromProgMem ? pgm_read_byte(bitmap + i) : *(bitmap+i));
}
i += rowBytes - rowBytesClipped;
}
timeoutSet(chunkHeight * dotPrintTime);
}
prevByte = '\n';
}
Your sketch will need to understand the data coming from the PHP and know when to send individual characters as bytes with printer.write() and when to send bytes as an image with printer.printBitmap(). This way the printer is receiving the proper commands to prep it for printing the appropriate data. You will need to construct some metadata around what you want to print in PHP and send that to the Arduino. A JSON format might look like this:
{"reciept": [
{
"type": "text",
"style": "bold",
"value": "Thank you for your purchase"
},
{
"type": "bitmap",
"pos": "center",
"value": ".... binary data ..."
}
]}
Now your Arduino sketch will understand when to send bytes individually as text and when to send a lot of data as a bitmap.
A more compact format might use line feeds as a break between segments:
F|bold
T|Thank you for shopping with us\r
P|Center
B|...binary data (with \r escaped)... \r
Or, you can send the amount of data with each segment to avoid escaping binary data much like the Content-Length header of HTTP
F4|boldT32|Thank you for shopping with us\rP6|CenterB3000|...binary data...