diff --git a/usb_application/constants.py b/usb_application/constants.py
index ac5a0a2..5013fd2 100644
--- a/usb_application/constants.py
+++ b/usb_application/constants.py
@@ -20,3 +20,7 @@
 ATR_SYSMOCOM2 = array('B', [0x3B, 0x99, 0x11, 0x00, 0x11, 0x88, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x60])
 NEW_ATR = ATR_SYSMOCOM2
 ATR_STRANGE_SIM = array('B', [0x3B, 0x0B, 0x00, 0x20, 0x00, 0x00, 0x00, 0x00, 0x68, 0x2E, 0x00, 0x20, 0x68])
+
+# USB errors
+ERR_TIMEOUT = 110
+ERR_NO_SUCH_DEV = 19