如何从POS打印机获取状态

Question

我试图找到一种方法从POS打印机获取纸张状态;我想我会使用GS a，GS r序列，但我无法理解如何从打印机返回信息;我在Linux下，POS打印机返回有关状态的信息？

Answer 1

我终于解决了我的问题...我使用PHP在Linux中，这里是代码，希望能帮助人：

<?php 

$device="/dev/usb/lp0"; 
$printer=fopen($device, 'w'); 

//La sequenza di ESCAPE DLE EOT n consente 
//la trasmissione in realtime 
//dello status 
//n=1: printer status 
//n=2: printer offline status 
//n=3: error status 
//n=4: paper roll sensor status 

//Per n=4 i bits valorizzati sono: 
//BIT Off/On Dec Desc 
//0  Off  0 not used, fixed to Off 
//1  On  2 not used, fixed to On 
//2,3 Off  0 Paper adequate 
//2,3 On  12 Paper near end detected 
//4  On  16 Not used, fixed to On 
//5,6 Off  0 Paper present 
//5,6 Off  96 Paper roll end 
//7  Off  0 Not used, fixed to Off 


fwrite($printer,kbyte(16).kbyte(4).kbyte(4)); 
//fwrite($printer,kbyte(29).kbyte(73).kbyte(69)); 

fclose($printer); 
$r_printer=fopen($device, 'r'); 
$ret=fgets($r_printer); 
fclose($r_printer); 
$bit_val=ord($ret[0]); 

print "Retval=".$bit_val; 

if(($bit_val & 12) || ($bit_val & 96)) 
    print "******Out of paper******\n"; 
else 
    print "---Paper ok\n"; 

function kbyte($num) { 
    return pack('C', $num); 
} 
?>