diff --git a/README.md b/README.md
index e4d48b6..2e8dc65 100644
--- a/README.md
+++ b/README.md
@@ -12,8 +12,8 @@ MAIN (antenna on the left)
         (○) TP6/VCC
 
            TP2/RX (○)
-                                 (○) ?
-        TP1/TX (○)   (○) ?
+                                 (○) I2C bus
+        TP1/TX (○)   (○) I2C bus