Added dependencies to get_sdk.sh. Cleaned up code in enter_download_mode.py and made compatible with py2 and py3.

board/get_sdk.sh

@@ -1,2 +1,3 @@
 #!/bin/bash
-sudo apt-get install gcc-arm-none-eabi
+sudo apt-get install gcc-arm-none-eabi python-pip
+sudo pip2 install libusb1

board/tools/enter_download_mode.py

@@ -1,27 +1,33 @@
 #!/usr/bin/env python
-import usb1
+from __future__ import print_function
+
+import sys
 import time
-import traceback
+import usb1
 
-if __name__ == "__main__":
-  context = usb1.USBContext()
-
-  handle = None
-  for device in context.getDeviceList(skip_on_error=True):
-    if device.getVendorID() == 0xbbaa and device.getProductID()&0xFF00 == 0xdd00:
-      print "found device"
-      handle = device.open()
-      handle.claimInterface(0)
-      break
-
-  if handle == None:
-    print "no device found"
-    exit(0)
+def enter_download_mode(device):
+  handle = device.open()
+  handle.claimInterface(0)
 
   try:
-    handle.controlWrite(usb1.TYPE_VENDOR | usb1.RECIPIENT_DEVICE, 0xd1, 0, 0, '')
-  except Exception:
-    traceback.print_exc()
-    print "expected error, exiting cleanly"
-  time.sleep(1)
+    handle.controlWrite(usb1.TYPE_VENDOR | usb1.RECIPIENT_DEVICE, 0xd1, 0, 0, b'')
+  except usb1.USBErrorIO as e:
+    print("Device download mode enabled.")
+    time.sleep(1)
+  else:
+    print("Device failed to enter download mode.")
+    sys.exit(1)
 
+def find_first_panda(context=None):
+  context = context or usb1.USBContext()
+  for device in context.getDeviceList(skip_on_error=True):
+    if device.getVendorID() == 0xbbaa and device.getProductID()&0xFF00 == 0xdd00:
+      return device
+
+if __name__ == "__main__":
+  panda_dev = find_first_panda()
+  if panda_dev == None:
+    print("no device found")
+    sys.exit(0)
+  print("found device")
+  enter_download_mode(panda_dev)