diff --git a/include/mraa_adv_func.h b/include/mraa_adv_func.h
index a8eb8045a..e237ef9df 100644
--- a/include/mraa_adv_func.h
+++ b/include/mraa_adv_func.h
@@ -64,9 +64,9 @@ typedef struct {
     mraa_result_t (*i2c_set_frequency_replace) (mraa_i2c_context dev, mraa_i2c_mode_t mode);
     mraa_result_t (*i2c_address_replace) (mraa_i2c_context dev, uint8_t addr);
     int (*i2c_read_replace) (mraa_i2c_context dev, uint8_t* data, int length);
-    uint8_t (*i2c_read_byte_replace) (mraa_i2c_context dev);
-    uint8_t (*i2c_read_byte_data_replace) (mraa_i2c_context dev, const uint8_t command);
-    uint16_t (*i2c_read_word_data_replace) (mraa_i2c_context dev, const uint8_t command);
+    int (*i2c_read_byte_replace) (mraa_i2c_context dev);
+    int (*i2c_read_byte_data_replace) (mraa_i2c_context dev, const uint8_t command);
+    int (*i2c_read_word_data_replace) (mraa_i2c_context dev, const uint8_t command);
     int (*i2c_read_bytes_data_replace) (mraa_i2c_context dev, uint8_t command, uint8_t* data, int length);
     mraa_result_t (*i2c_write_replace) (mraa_i2c_context dev, const uint8_t* data, int length);
     mraa_result_t (*i2c_write_byte_replace) (mraa_i2c_context dev, uint8_t data);
diff --git a/src/firmata/firmata_mraa.c b/src/firmata/firmata_mraa.c
index 9e173b9af..25dd9f584 100644
--- a/src/firmata/firmata_mraa.c
+++ b/src/firmata/firmata_mraa.c
@@ -191,7 +191,7 @@ mraa_firmata_i2c_wait(int addr, int reg)
     return MRAA_SUCCESS;
 }
 
-static uint8_t
+static int
 mraa_firmata_i2c_read_byte(mraa_i2c_context dev)
 {
     if (mraa_firmata_send_i2c_read_req(dev, 1) == MRAA_SUCCESS) {
@@ -199,10 +199,10 @@ mraa_firmata_i2c_read_byte(mraa_i2c_context dev)
             return firmata_dev->i2cmsg[dev->addr][0];
         }
     }
-    return 0;
+    return -1;
 }
 
-static uint16_t
+static int
 mraa_firmata_i2c_read_word_data(mraa_i2c_context dev, uint8_t command)
 {
     if (mraa_firmata_send_i2c_read_reg_req(dev, command, 2) == MRAA_SUCCESS) {
@@ -215,10 +215,10 @@ mraa_firmata_i2c_read_word_data(mraa_i2c_context dev, uint8_t command)
             data = (data << 8) & 0xFF00;
             data |= high;
 
-            return data;
-    }
+            return (int) data;
+        }
     }
-    return 0;
+    return -1;
 }
 
 static int
@@ -249,16 +249,16 @@ mraa_firmata_i2c_read(mraa_i2c_context dev, uint8_t* data, int length)
     return 0;
 }
 
-static uint8_t
+static int
 mraa_firmata_i2c_read_byte_data(mraa_i2c_context dev, uint8_t command)
 {
     if (mraa_firmata_send_i2c_read_reg_req(dev, command, 1) == MRAA_SUCCESS) {
         if (mraa_firmata_i2c_wait(dev->addr, command) == MRAA_SUCCESS) {
-            return firmata_dev->i2cmsg[dev->addr][command];
+            return (int) firmata_dev->i2cmsg[dev->addr][command];
         }
     }
 
-    return 0;
+    return -1;
 }
 
 static mraa_result_t
diff --git a/src/usb/ftdi_ft4222.c b/src/usb/ftdi_ft4222.c
index 5c6167e10..cb903e681 100644
--- a/src/usb/ftdi_ft4222.c
+++ b/src/usb/ftdi_ft4222.c
@@ -550,17 +550,17 @@ mraa_ftdi_ft4222_i2c_read(mraa_i2c_context dev, uint8_t* data, int length)
     return bytes_read;
 }
 
-static uint8_t
+static int
 mraa_ftdi_ft4222_i2c_read_byte(mraa_i2c_context dev)
 {
     uint8_t data;
     pthread_mutex_lock(&ft4222_lock);
     int bytes_read = mraa_ftdi_ft4222_i2c_context_read(dev, &data, 1);
     pthread_mutex_unlock(&ft4222_lock);
-    return bytes_read == 1 ? data : 0;
+    return bytes_read == 1 ? data : -1;
 }
 
-static uint8_t
+static int
 mraa_ftdi_ft4222_i2c_read_byte_data(mraa_i2c_context dev, uint8_t command)
 {
     uint8_t data;
@@ -570,10 +570,13 @@ mraa_ftdi_ft4222_i2c_read_byte_data(mraa_i2c_context dev, uint8_t command)
     if  (bytesWritten == 1)
        bytes_read = mraa_ftdi_ft4222_i2c_context_read(dev, &data, 1);
     pthread_mutex_unlock(&ft4222_lock);
-    return (bytes_read == 1) ? data : 0;
+    if (bytes_read == 1) {
+        return (int) data;
+    }
+    return -1;
 }
 
-static uint16_t
+static int
 mraa_ftdi_ft4222_i2c_read_word_data(mraa_i2c_context dev, uint8_t command)
 {
     uint8_t buf[2];
@@ -584,8 +587,10 @@ mraa_ftdi_ft4222_i2c_read_word_data(mraa_i2c_context dev, uint8_t command)
     if (bytes_written == 1)
        bytes_read = mraa_ftdi_ft4222_i2c_context_read(dev, buf, 2);
     pthread_mutex_unlock(&ft4222_lock);
-    data = (bytes_read == 2) ? *(uint16_t*)buf : 0;
-    return data;
+    if (bytes_read == 2) {
+        return (int) data;
+    }
+    return -1;
 }
 
 static int
@@ -600,7 +605,6 @@ mraa_ftdi_ft4222_i2c_read_bytes_data(mraa_i2c_context dev, uint8_t command, uint
     return bytes_read;
 }
 
-
 static mraa_result_t
 mraa_ftdi_ft4222_i2c_write(mraa_i2c_context dev, const uint8_t* data, int bytesToWrite)
 {
@@ -618,7 +622,6 @@ mraa_ftdi_ft4222_i2c_write_byte(mraa_i2c_context dev, uint8_t data)
     return status;
 }
 
-
 static mraa_result_t
 mraa_ftdi_ft4222_i2c_write_byte_data(mraa_i2c_context dev, const uint8_t data, const uint8_t command)
 {