diff --git a/df_datalink_sp/src/system_monitor.c b/df_datalink_sp/src/system_monitor.c
index 8b47b8a..feb9a7e 100644
--- a/df_datalink_sp/src/system_monitor.c
+++ b/df_datalink_sp/src/system_monitor.c
@@ -16,9 +16,9 @@
 
 typedef struct
 {
-	int8_t latest;
-	int8_t rBusy;
-	int8_t wBusy;
+	uint8_t latest;
+	uint8_t rBusy;
+	uint8_t wBusy;
 } PINGPONG;
 
 typedef struct