diff --git a/README.md b/README.md
index d8fb42a..41da05b 100644
--- a/README.md
+++ b/README.md
@@ -11,8 +11,19 @@ Arduino based project running on my custom made board
 **The modules :**
 ![](http://88.167.116.148/images/git/SAB_cmp_mod.png)
 
-### Hardware pin mapping
+### Hardware pin mapping :
+![](http://88.167.116.148/images/git/ESP8266_pinout.png)
+(This image wasn't done by me)
 
+**So we have :**
+* I2C (for OLED screen and RTC)
+    * GPIO4 --> SDA
+    * GPIO5 --> SCL
+* SPI (for µSDCard)
+    * GPIO13 --> MOSI
+    * GPIO12 --> MISO
+    * GPIO14 --> CLK
+    * GPIO2 --> µSDCard CHIP_SELECT
 
 ## Here is a list of the components needed in order to build such a board :
 * 1x 1N4001 reverse voltage protection diode