diff --git a/extras/i2c/i2c.c b/extras/i2c/i2c.c
index a41dff7..7fbae65 100644
--- a/extras/i2c/i2c.c
+++ b/extras/i2c/i2c.c
@@ -27,10 +27,13 @@
 #include <espressif/esp_system.h>
 #include "i2c.h"
 
+//#define I2C_DEBUG true
 
-// I2C driver for ESP8266 written for use with esp-open-rtos
-// Based on https://en.wikipedia.org/wiki/I²C#Example_of_bit-banging_the_I.C2.B2C_Master_protocol
-// With calling overhead, we end up at ~320kbit/s
+#ifdef I2C_DEBUG
+#define debug(fmt, ...) printf("%s: " fmt "\n", "I2C", ## __VA_ARGS__)
+#else
+#define debug(fmt, ...)
+#endif
 
 #define CLK_STRETCH  (10)
 
@@ -38,6 +41,11 @@ static bool started;
 static uint8_t g_scl_pin;
 static uint8_t g_sda_pin;
 
+inline bool i2c_status(void)
+{
+    return started;
+}
+
 void i2c_init(uint8_t scl_pin, uint8_t sda_pin)
 {
     started = false;
@@ -110,14 +118,14 @@ void i2c_start(void)
         // Repeated start setup time, minimum 4.7us
         i2c_delay();
     }
+    started = true;
     if (read_sda() == 0) {
-        printf("I2C: arbitration lost in i2c_start\n");
+        debug("arbitration lost in i2c_start");
     }
     // SCL is high, set SDA from 1 to 0.
     clear_sda();
     i2c_delay();
     clear_scl();
-    started = true;
 }
 
 // Output stop condition
@@ -133,7 +141,7 @@ void i2c_stop(void)
     i2c_delay();
     // SCL is high, set SDA from 0 to 1
     if (read_sda() == 0) {
-        printf("I2C: arbitration lost in i2c_stop\n");
+        debug("arbitration lost in i2c_stop");
     }
     i2c_delay();
     started = false;
@@ -154,7 +162,7 @@ static void i2c_write_bit(bool bit)
     // SCL is high, now data is valid
     // If SDA is high, check that nobody else is driving SDA
     if (bit && read_sda() == 0) {
-        printf("I2C: arbitration lost in i2c_write_bit\n");
+        debug("arbitration lost in i2c_write_bit");
     }
     i2c_delay();
     clear_scl();
@@ -203,6 +211,7 @@ uint8_t i2c_read(bool ack)
 bool i2c_slave_write(uint8_t slave_addr, uint8_t *data, uint8_t len)
 {
     bool success = false;
+    if (i2c_status()) return success ; // If bus busy, dont write
     do {
         i2c_start();
         if (!i2c_write(slave_addr << 1))
@@ -220,6 +229,7 @@ bool i2c_slave_write(uint8_t slave_addr, uint8_t *data, uint8_t len)
 bool i2c_slave_read(uint8_t slave_addr, uint8_t data, uint8_t *buf, uint32_t len)
 {
     bool success = false;
+    if (i2c_status()) return success ; // If bus busy, dont read
     do {
         i2c_start();
         if (!i2c_write(slave_addr << 1)) {
@@ -240,7 +250,7 @@ bool i2c_slave_read(uint8_t slave_addr, uint8_t data, uint8_t *buf, uint32_t len
     } while(0);
     i2c_stop();
     if (!success) {
-        printf("I2C: write error\n");
+        debug("write error");
     }
     return success;
 }
diff --git a/extras/i2c/i2c.h b/extras/i2c/i2c.h
index bfb3811..8654594 100644
--- a/extras/i2c/i2c.h
+++ b/extras/i2c/i2c.h
@@ -32,26 +32,71 @@
 extern "C" {
 #endif
 
-// Init bitbanging I2C driver on given pins
+// I2C driver for ESP8266 written for use with esp-open-rtos
+// Based on https://en.wikipedia.org/wiki/I²C#Example_of_bit-banging_the_I.C2.B2C_Master_protocol
+// With calling overhead, we end up at ~320kbit/s
+
+///////Level 0 API
+
+/**
+ * Init bitbanging I2C driver on given pins
+ * @param scl_pin SCL pin for I2C
+ * @param sda_pin SDA pin for I2C
+ */
 void i2c_init(uint8_t scl_pin, uint8_t sda_pin);
 
-// Write a byte to I2C bus. Return true if slave acked.
+/**
+ * Write a byte to I2C bus.
+ * @param byte Pointer to device descriptor
+ * @return true if slave acked
+ */
 bool i2c_write(uint8_t byte);
 
-// Read a byte from I2C bus. Return true if slave acked.
+/**
+ * Read a byte from I2C bus.
+ * @param ack Set Ack for slave (false: Ack // true: NoAck)
+ * @return byte read from slave.
+ */
 uint8_t i2c_read(bool ack);
 
-// Write 'len' bytes from 'buf' to slave. Return true if slave acked.
+/**
+ * Send start or restart condition
+ */
+void i2c_start(void);
+
+/**
+ * Send stop condition
+ */
+void i2c_stop(void);
+
+/**
+ * get status from I2C bus.
+ * @return true if busy.
+ */
+bool i2c_status(void);
+
+///////Level 1 API (Don't need functions above)
+
+/**
+ * Write 'len' bytes from 'buf' to slave. Return true if slave acked.
+ * @param slave_addr slave device address
+ * @param buf Pointer to data buffer
+ * @param len Number of byte to send
+ * @return false if error occured
+ */
 bool i2c_slave_write(uint8_t slave_addr, uint8_t *buf, uint8_t len);
 
-// Issue a read operation and send 'data', followed by reading 'len' bytes
-// from slave into 'buf'. Return true if slave acked.
+/**
+ * Issue a read operation and send 'data', followed by reading 'len' bytes
+ * from slave into 'buf'.
+ * @param slave_addr slave device address
+ * @param data register address to send
+ * @param buf Pointer to data buffer
+ * @param len Number of byte to read
+ * @return false if error occured
+ */
 bool i2c_slave_read(uint8_t slave_addr, uint8_t data, uint8_t *buf, uint32_t len);
 
-// Send start and stop conditions. Only needed when implementing protocols for
-// devices where the i2c_slave_[read|write] functions above are of no use.
-void i2c_start(void);
-void i2c_stop(void);
 
 #ifdef	__cplusplus
 }