diff --git a/README.md b/README.md
index c2b73c4..281f5a6 100644
--- a/README.md
+++ b/README.md
@@ -4,5 +4,21 @@ the Arduino IDE and uses an onboard ESP32 as its Wi-Fi transmitter.
 
 ![ESP2 Board](1.png)
 
-# AA
-ss 
+# PCB
+The overall design of the PCB is quite simple. The CPU is powered and programmed through the panel-mount USB
+connector. The CPUs USB pin supplies the board's power bus with 5V.
+
+![Pool Kit PCB](2.png)
+
+# Communication protocol
+The CPU communicates with all peripheral sensors using the I2C data protocol. All data lines are directly connected
+to the CPUs I2C port. Using a different data protocol with this circuit board is not possible.
+
+It is important to keep in mind that all Atlas Scientific components default to UART mode. When adding a new 
+Atlas Scientific component to the kit, it must first be put into I2C mode.
+
+Adding additional components of the same type, such as an additional pH or ORP sensor, is not hard to do. As
+mentioned above, you must set the device to I2C mode, and you must make sure that its I2C address is not the same 
+as the already existing components.
+
+The next table lists the default I2C address of Atlas Scientific components commonly added to this kit.