added NanoPi Duo support

README-nanopiduo-support.md

@@ -0,0 +1,15 @@
+# README_npiduo.md
+Lukas, 2019-12-04
+# to use WiringNP with NanoPiDuo and armbian ubuntu 18.04
+added nanopi duo board support due to error:
+  $gpio readall
+  piBoardRev: Unable to determine board revision from /proc/cpuinfo
+  -> Is not NanoPi based board.
+  ->  You may want to check:
+  ->  http://www.lemaker.org/
+  open /sys/class/sunxi_info/sys_info failed.
+
+## WiringNP fix
+https://forum.armbian.com/topic/11426-wiringpi-for-nanopi-neo-air/
+1. copy sys_info to /etc
+2. normally build the project

sys_info

@@ -0,0 +1,6 @@
+sunxi_platform    : Sun8iw7p1
+sunxi_secure      : normal
+sunxi_chipid      : 2c21020e786746240000540000000000
+sunxi_chiptype    : 00000042
+sunxi_batchno     : 1
+sunxi_board_id    : 4(0) 

wiringPi/boardtype_friendlyelec.c

@@ -157,8 +157,8 @@ static int getAllwinnerBoardID(char* boardId, int boardIdMaxLen )
     FILE *f;
     int ret = -1;
 
-    if (!(f = fopen("/sys/class/sunxi_info/sys_info", "r"))) {
+    if (!(f = fopen("/etc/sys_info", "r"))) {
-        LOGE("open /sys/class/sunxi_info/sys_info failed.");
+        LOGE("open /etc/sys_info failed.");
         return -1;
     }