fix display firmware load

+ add remark about test mode in README

README.md

@@ -145,7 +145,17 @@ which image?
 * remove the stick, power off/on (or do `sudo reboot now`)
 
 
-### e) Install Services
+### e) Install Display Firmware (control box only)
+
+display in test mode?
+- finish it by touching several times
+
+> cd boxtools
+> git pull
+> sudo python3 display.py fw_display.bin
+
+
+### f) Install Services
 
 login with root/FrappyLinse
 ```

display.py

@@ -51,9 +51,6 @@ WIDTH = 480
 MAGIC = b'\xcb\xef\x20\x18'
 
 
-mainif = MainIf()
-
-
 def xy(x, y):
     x = min(480, int(x))
     return bytes([(min(127, y + TOPGAP) << 1) + (x >> 8), x % 256])
@@ -266,9 +263,12 @@ for arg in sys.argv[1:]:
     elif tty.startswith('/dev/'):
         tty = arg
     else:
-        raise ValueError(f'do not know how to tread argument: {arg}')
+        raise ValueError(f'do not know how to treat argument: {arg}')
 
 
+if not firmware:
+    mainif = MainIf()
+
 d = Display(tty, daemon=daemon and not firmware)
 if firmware:
     with open(firmware, 'rb') as f: