diff --git a/README.md b/README.md
index d7fc1a4..9e332fb 100644
--- a/README.md
+++ b/README.md
@@ -88,6 +88,10 @@ sequenceDiagram
     end
 ```
 
+### Serial
+
+The A9 cameras have a TX/RX test points - connecting with UART at 921600 81N gives _read only_ access to some debug logs.
+
 ### Discrepancies between cameras
 
 1. Wifi Strength