diff --git a/Arduino/epd2in7/epdif.h b/Arduino/epd2in7/epdif.h
index c195910..010b9ea 100644
--- a/Arduino/epd2in7/epdif.h
+++ b/Arduino/epd2in7/epdif.h
@@ -33,7 +33,7 @@
 // Pin definition
 #define RST_PIN         8
 #define DC_PIN          9
-#define CS_PIN          10
+#define CS_PIN          SS
 #define BUSY_PIN        7
 
 class EpdIf {
diff --git a/Arduino/epd2in7b/epdif.h b/Arduino/epd2in7b/epdif.h
index c195910..010b9ea 100644
--- a/Arduino/epd2in7b/epdif.h
+++ b/Arduino/epd2in7b/epdif.h
@@ -33,7 +33,7 @@
 // Pin definition
 #define RST_PIN         8
 #define DC_PIN          9
-#define CS_PIN          10
+#define CS_PIN          SS
 #define BUSY_PIN        7
 
 class EpdIf {