Add documentation on the physical connector

Connector.md

@@ -0,0 +1,27 @@
+# Connector
+
+The connector is a RJ12 (6P6C, phone connector with all 6 positions populated)
+The interface uses RS-232 levels (±15V)
+
+## Pinout
+
+Seen from the end of the RJ12 plug
+
+```text
+    ┌───┐
+┌───┘   └───┐
+│           │
+├─┬─┬─┬─┬─┬─┤
+│1│2│3│4│5│6│
+└─┴─┴─┴─┴─┴─┘
+```
+
+1. TX
+2. RX
+3. GND
+4. GND
+5. +V
+6. +V
+
+`+V` seems to be a regulated 14.6V supply, current limited by a 100Ω resistor
+`RX` and `TX` has 100Ω resistors in series.

Protocol.md

@@ -60,9 +60,9 @@ This particular memory section contains the device SKU: ML2420
    ┌──────────────┐
  ╔═╡ Transfer ID? │
  ║ └──────────────┘
- ║    ┌────────────────────┐
- ║  ╔═╡ Operation (6=read) │
- ║  ║ └────────────────────┘
+ ║    ┌─────────────────────┐
+ ║  ╔═╡ Operation (6=write) │
+ ║  ║ └─────────────────────┘
  ║  ║      ┌─────────┐
  ║  ║    ╔═╡ Address │
  ║  ║    ║ └─────────┘