Merge pull request 'fix for printer standby' (#13) from wait_for_printer into main

Reviewed-on: #13

README.md

@@ -33,8 +33,9 @@ systemctl enable --now /lib/systemd/system/reHDDPrinter.service
 - Brother QL-570
 - Paper With: 62mm or 696px
 
+**Hint: Some Brother printers have enabled standby mode. This will disconnect the printer. See [Issue #12](https://git.mosad.xyz/localhorst/reHDDPrinter/issues/12) to disable standby.**
 
-see https://github.com/pklaus/brother_ql
+see https://github.com/pklaus/brother_ql for details for printer access
 
 
 

reHDDPrinter.py

@@ -9,6 +9,7 @@
 import sysv_ipc 
 import pycstruct
 import os
+import time
 from brother_ql.brother_ql_create import create_label
 from brother_ql.raster import BrotherQLRaster
 import layouter
@@ -17,6 +18,7 @@ str_buffer_size = 64        #keep this synchronous to reHDD
 msg_queue_key = 0x1B11193C0 #keep this synchronous to reHDD
 
 file_name = "output.png"
+printer_path = "/dev/usb/lp0"
 
 def get_struct_format():
     #keep this synchronous to struct in reHDD
@@ -57,10 +59,15 @@ def main():
             shred_timestamp=int(driveData['driveShredTimestamp']),\
             shred_duration=int(driveData['driveShredDuration']))
 
+            while(not os.path.exists(printer_path)):
+                print("Printer not found, waiting ...")
+                time.sleep(30) #sleep 30
+
             layouter.generate_image(drive, rehdd_info, file_name)
             qlr = BrotherQLRaster("QL-570")
             create_label(qlr, file_name, '62')
-            with open("/dev/usb/lp0", 'wb') as file:
+
+            with open(printer_path, 'wb') as file:
                 file.write(qlr.data)
             os.remove(file_name)
     except sysv_ipc.ExistentialError: