diff --git a/code/firmware/user/src/i2c.c b/code/firmware/user/src/i2c.c
index 3620857..767c46f 100644
--- a/code/firmware/user/src/i2c.c
+++ b/code/firmware/user/src/i2c.c
@@ -15,7 +15,10 @@
 
 
 
-#define I2C_TIMEOUT 0xffff;
+#define I2C_TIMEOUT             0xffff
+#define I2C_TIMEOUT_ACK_POLL    0x180
+
+static uint32_t timeout;
 
 
 void i2c_init()
@@ -42,25 +45,36 @@ void i2c_init()
 /*
  * reads data from devices which use a single-byte address
  */
-void i2c_read_addr1b(uint8_t devaddr, uint8_t addr, uint8_t *data, uint8_t len)
+int8_t i2c_read_addr1b(uint8_t devaddr, uint8_t addr, uint8_t *data, uint8_t len)
 {
-    while(I2C_GetFlagStatus(I2C1, I2C_FLAG_BUSY) != RESET);
+    timeout = I2C_TIMEOUT;
+    while((I2C_GetFlagStatus(I2C1, I2C_FLAG_BUSY) != RESET) && timeout--);
+    if (!timeout) return -1;
+
     I2C_GenerateSTART(I2C1, ENABLE);
+    timeout = I2C_TIMEOUT;
+    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_MODE_SELECT) && timeout--);
+    if (!timeout) return -2;
 
-    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_MODE_SELECT));
     I2C_Send7bitAddress(I2C1, devaddr, I2C_Direction_Transmitter);
-
-    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED));
+    timeout = I2C_TIMEOUT;
+    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED) && timeout--);
+    if (!timeout) return -3;
 
     I2C_SendData(I2C1, addr);
-    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_BYTE_TRANSMITTED));
+    timeout = I2C_TIMEOUT;
+    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_BYTE_TRANSMITTED) && timeout--);
+    if (!timeout) return -4;
 
     I2C_GenerateSTART(I2C1, ENABLE);
+    timeout = I2C_TIMEOUT;
+    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_MODE_SELECT) && timeout--);
+    if (!timeout) return -5;
 
-    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_MODE_SELECT));
     I2C_Send7bitAddress(I2C1, devaddr, I2C_Direction_Receiver);
-
-    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_RECEIVER_MODE_SELECTED));
+    timeout = I2C_TIMEOUT;
+    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_RECEIVER_MODE_SELECTED) && timeout--);
+    if (!timeout) return -6;
 
     while (len) {
        while(I2C_GetFlagStatus(I2C1, I2C_FLAG_RXNE) == RESET) {
@@ -74,20 +88,30 @@ void i2c_read_addr1b(uint8_t devaddr, uint8_t addr, uint8_t *data, uint8_t len)
            I2C_GenerateSTOP(I2C1, ENABLE);
        }
     }
+
+    return 0;
 }
 
-void i2c_write_addr1b(uint8_t devaddr, uint8_t addr, uint8_t *data, uint8_t len)
+int8_t i2c_write_addr1b(uint8_t devaddr, uint8_t addr, uint8_t *data, uint8_t len)
 {
-    while(I2C_GetFlagStatus(I2C1, I2C_FLAG_BUSY) != RESET);
+    timeout = I2C_TIMEOUT;
+    while((I2C_GetFlagStatus(I2C1, I2C_FLAG_BUSY) != RESET) && timeout--);
+    if (!timeout) return -1;
+
     I2C_GenerateSTART(I2C1, ENABLE);
+    timeout = I2C_TIMEOUT;
+    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_MODE_SELECT) && timeout--);
+    if (!timeout) return -2;
 
-    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_MODE_SELECT));
     I2C_Send7bitAddress(I2C1, devaddr, I2C_Direction_Transmitter);
-
-    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED));
+    timeout = I2C_TIMEOUT;
+    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED) && timeout--);
+    if (!timeout) return -3;
 
     I2C_SendData(I2C1, addr);
-    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_BYTE_TRANSMITTED));
+    timeout = I2C_TIMEOUT;
+    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_BYTE_TRANSMITTED) && timeout--);
+    if (!timeout) return -4;
 
     while (len) {
         while(I2C_GetFlagStatus(I2C1, I2C_FLAG_TXE) != RESET) {
@@ -98,20 +122,29 @@ void i2c_write_addr1b(uint8_t devaddr, uint8_t addr, uint8_t *data, uint8_t len)
     }
 
     I2C_GenerateSTOP(I2C1, ENABLE);
+
+    return 0;
 }
 
 int8_t i2c_ack_poll(uint8_t devaddr)
 {
     int8_t addr_match = 0;
 
-    while(I2C_GetFlagStatus(I2C1, I2C_FLAG_BUSY) != RESET);
+    timeout = I2C_TIMEOUT;
+    while((I2C_GetFlagStatus(I2C1, I2C_FLAG_BUSY) != RESET) && timeout--);
+    if (!timeout) return -1;
+
     I2C_GenerateSTART(I2C1, ENABLE);
+    timeout = I2C_TIMEOUT;
+    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_MODE_SELECT) && timeout--);
+    if (!timeout) return -2;
 
-    while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_MODE_SELECT));
     I2C_Send7bitAddress(I2C1, devaddr, I2C_Direction_Receiver);
-
-    if (!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_RECEIVER_MODE_SELECTED))
-        addr_match = -1;
+    timeout = I2C_TIMEOUT_ACK_POLL;
+    while (!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_RECEIVER_MODE_SELECTED) && timeout--);
+    if (!timeout) {
+        addr_match = -128;
+    }
 
     I2C_GenerateSTOP(I2C1, ENABLE);