Amazon ALEXA Lists Exercise – Put’em on Paper…

4.6 Alternative: use your Fritz!Box as print server

In case you don’t want a separate Pi, but do have a router, e.g. a Fritz!Box, you can most likely use that one as print server. I own a 7490 and simply by plugging in the printer, it would be available under the Fritz!Box‘ ip address, e.g. 192.168.175.1 , or its host name, fritz.box , and the RAW port number 9100 .

The ESC/POS code supports this RAW network interface through a separate printer interface, here’s the code.

<?php
	// small obscurity secret checking...
	$localsecret = "1234567890__REPLACE__WITH__YOUR__SECRET__1234567890";
	if ($localsecret != $_REQUEST["secret"]) {
		header("HTTP/1.1 403 Unauthorized");
		exit(1);
	}
	// small obscurity secret checking...
	$listName  = urlencode($_REQUEST["listName"]);
	$listItems = json_decode($_REQUEST["listItems"]);

	if (!is_array($listItems) || count($listItems)<1 || count($listItems)>50) {
		header("HTTP/1.1 400 Bad Request");
		$error = array(
			"statusCode"=>400,
			"statusText"=>"Please provide at least 1 and at best 50 list item(s) in request parameter named 'listItems' in form of a JSON UTF8 list.",
			"listName"=>$_REQUEST["listName"],
			"listItems"=>$_REQUEST["listItems"]
		);
		echo json_encode($error);
		exit(2);
	}
	// print the crap...
	require __DIR__ . '/escpos/autoload.php';
	use Mike42\Escpos\PrintConnectors\NetworkPrintConnector;
	use Mike42\Escpos\Printer;
	// ***** USE THE NETWORK PRINTER
	$connector = new NetworkPrintConnector("fritz.box", 9100);
	$printer = new Printer($connector);
	if ($printer==null) {
		header("HTTP/1.1 503 Service Unavailable");
		$error = array(
			"statusCode"=>500,
			"statusText"=>"No thermal printer connected."
		);
		echo json_encode($error);
		exit(1);
	}
	// ***** INPUT SANITY CHECKING
	$listItems = json_decode($_REQUEST["listItems"]);
	if (!is_array($listItems) || count($listItems)<1 || count($listItems)>50) {
		header("HTTP/1.1 400 Bad Request");
		$error = array(
			"statusCode"=>400,
			"statusText"=>"Please provide at least 1 and at best 50 list item(s) in request parameter named 'listItems' in form of a JSON UTF8 list."
		);
		echo json_encode($error);
		die(1);
	}
	
	$listName = mb_strtoupper($_REQUEST["listName"]);
	// make a default
	if ($listName=="") { $listName = "UNBENANNTE LISTE"; }
	// truncate to 32 chars
	if (mb_strlen($listName)>32) { $listName = mb_substr($listName, 0, 16); }
	// Set print mode to double height only
	if (mb_strlen($listName)<=16) {
		$printer -> selectPrintMode(Printer::MODE_DOUBLE_HEIGHT|Printer::MODE_DOUBLE_WIDTH);
	} else {
		$printer -> selectPrintMode(Printer::MODE_DOUBLE_HEIGHT);
	}
	// **** PRINT THE HEADER
	$printer -> setJustification(Printer::JUSTIFY_CENTER);
	$printer -> setEmphasis(true);
	$printer -> text($listName."\n");
	$printer -> selectPrintMode();
	// **** PRINT THE DIME (10.10.2017  16:43)
	$printer -> setReverseColors(true);
	$printer -> text(date("---- d.m.Y ----- H:i ----\n"));
	$printer -> setReverseColors(false);
	$printer -> setEmphasis(false);
	$printer -> setJustification(Printer::JUSTIFY_LEFT);
	$printer -> feed(1);
	// **** PRINT THE LIST
	foreach($listItems as $item) {
		$item = iconv("UTF-8", "CP437", $item); //required since now UTF8 characters are not printed correctly
		$item = "* ". ucwords(strtolower(mb_substr($item, 0, 30))) ."\n";
		$printer -> text($item);
	}
	$printer -> feed(5);
	$printer -> cut();
	$printer -> close();
	$error = array(
		"statusCode"=>200,
		"statusText"=>"List '$listName' was printed successfully."
	);
	echo json_encode($error);
?>

Note that you need to change the secret and the IP / host name for your print server.

Small caveat: In my case, the UTF-8 characters that were printing flawlessly on the Raspberry Pi print server, come out as two ASCII characters. A German ‚ü‘ for example would become two of the frame characters. I don’t know if it’s the printer connector’s fault or if there’s something wrong with the fritzbox code, but a work-around is using iConv to convert UTF8 to CP437. It has most of the German diacritics, so good enough for me.