diff --git a/misc/reverse_engineered_hardware/pressure_coupler/pressure_coupler.md b/misc/reverse_engineered_hardware/pressure_coupler/pressure_coupler.md
new file mode 100644
index 0000000..5f304af
--- /dev/null
+++ b/misc/reverse_engineered_hardware/pressure_coupler/pressure_coupler.md
@@ -0,0 +1,21 @@
+# Pressure coupler
+
+## Left side (facing front panel)
+
+From top to bottom:
+
+- input on/off -> connected to single white wire, switch is between that and ground
+- bridge balance -> connected to blue wire. This is a voltage divider between ground and VCC, read this with `analogRead()`
+- calibration -/off/+ -> connected to twisted white/orange wire, connects
+  the white wire to ground, nothing to ground or the orange wire to ground
+- multichoice switch -> has 16 positions, each yellow wire is a bit of the number of the position
+  so for example, if the switch is in the third position (so 2 when counting 0-based, or 0010 in binary),
+	wire 2 will be connected to ground, all other wires will be left floating
+
+Red is connected to VCC (5V), black to ground
+
+## Right side
+
+Switches are connected to white wires (2 positions) or white and orange wires (3 positions). Knobs are connected to blue wires.
+
+Switches connect to ground or keep wire floating. Knobs are a voltage divider between ground (black) and VCC (red).