From b24c1101b6ea1c94bb11e6a2e719289927959b9f Mon Sep 17 00:00:00 2001
From: Junzi Sun <junzisun@gmail.com>
Date: Fri, 14 Dec 2018 17:22:55 +0100
Subject: [PATCH] add DF 0 and 16 to altcode

---
 pyModeS/decoder/common.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pyModeS/decoder/common.py b/pyModeS/decoder/common.py
index 4225568..99384c4 100644
--- a/pyModeS/decoder/common.py
+++ b/pyModeS/decoder/common.py
@@ -205,8 +205,8 @@ def altcode(msg):
         int: altitude in ft
     """
 
-    if df(msg) not in [4, 20]:
-        raise RuntimeError("Message must be Downlink Format 4 or 20.")
+    if df(msg) not in [0, 4, 16, 20]:
+        raise RuntimeError("Message must be Downlink Format 0, 4, 16, or 20.")
 
     # Altitude code, bit 20-32
     mbin = hex2bin(msg)