diff --git a/notes/serial.txt b/notes/serial.txt
new file mode 100644
index 0000000..94e94e4
--- /dev/null
+++ b/notes/serial.txt
@@ -0,0 +1,3 @@
+ ground      | CTS  | RTS    | TX    | RX  | ground
+ uninsulated | blue | yellow | green | red | black
+             | D2   |  D3    | D1    | D0  |