add some doc for I2C

tenbaht · tenbaht · commit f04babd9ff2e · 2018-11-03T12:45:09.000+01:00
diff --git a/docs/api/I2C.md b/docs/api/I2C.md
@@ -8,5 +8,39 @@ deadlock situations, it allows for communication using a repeated start
 condition as required by some devices, the code is much more compact and the
 structure is easier to understand.
 
-The current state of the port does not include the deadlock protection,
-though.
+The current state of the port is quite incomplete. Missing parts:
+
+- read functions
+- speed setting (100kHz only)
+- pullup setting
+- does not include the deadlock protection
+
+
+## Error codes
+
+Return values for functions that use the timeOut feature will return at what
+point in the transmission the timeout occurred.
+
+All possible return values:
+
+Errorcode | Meaning
+---:	|---
+  0	|Function executed with no errors
+  1-7	|Timeout occurred, see above list
+  8-0xFF|See datasheet for exact meaning
+
+
+Looking at a full communication sequence between a master and slave
+(transmit data and then readback data) there a total of 7 points in the
+sequence where a timeout can occur. These are listed below and correspond to
+the returned value.
+
+Errorcode | Meaning: Waiting for...
+---:	|---
+  1	|Waiting for successful completion of a Start bit
+  2	|Waiting for ACK/NACK while addressing slave in transmit mode (MT)
+  3	|Waiting for ACK/NACK while sending data to the slave
+  4	|Waiting for successful completion of a Repeated Start
+  5	|Waiting for ACK/NACK while addressing slave in receiver mode (MR)
+  6	|Waiting for ACK/NACK while receiving data from the slave
+  7	|Waiting for successful completion of the Stop bit
