diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1e62a90..babec09 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -4,18 +4,17 @@ project(spidev-lib)
 set(CMAKE_CXX_FLAGS "-g -Wall")
 set(CMAKE_C_FLAGS "-g -Wall")
 
-include_directories(src/)
-
-
 add_library(spidev-lib src/spidev_lib.c)
-add_executable(
-     spi-testc sample/spidev-testc.c
-)
-target_link_libraries( spi-testc spidev-lib)
+target_include_directories(spidev-lib PUBLIC src/)
+
+add_executable(spi-testc sample/spidev-testc.c)
+target_link_libraries(spi-testc spidev-lib)
 
 add_library(spidev-lib++ src/spidev_lib++.cc)
+target_include_directories(spidev-lib++ PUBLIC src/)
+
 add_executable(spi-testcpp sample/spidev-testcpp.cc)
-target_link_libraries( spi-testcpp spidev-lib++ )
+target_link_libraries(spi-testcpp spidev-lib++)
 
 add_dependencies(spi-testcpp spidev-lib++)
 add_dependencies(spi-testc spidev-lib)
@@ -27,4 +26,3 @@ INSTALL(TARGETS  spidev-lib  spidev-lib++
 )
 INSTALL( FILES src/spidev_lib.h DESTINATION include)
 INSTALL( FILES src/spidev_lib++.h DESTINATION include)
-
diff --git a/src/spidev_lib++.cc b/src/spidev_lib++.cc
index b6f95d8..6f3e8d0 100644
--- a/src/spidev_lib++.cc
+++ b/src/spidev_lib++.cc
@@ -76,7 +76,7 @@ bool SPI::setMode(uint8_t p_mode){
 
 }
 
-int SPI::xfer(uint8_t *p_txbuffer, uint8_t p_txlen, uint8_t *p_rxbuffer, uint8_t p_rxlen){
+int SPI::xfer(uint8_t *p_txbuffer, uint32_t p_txlen, uint8_t *p_rxbuffer, uint32_t p_rxlen){
     struct spi_ioc_transfer spi_message[1];
     memset(spi_message, 0, sizeof(spi_message));
     
@@ -86,7 +86,7 @@ int SPI::xfer(uint8_t *p_txbuffer, uint8_t p_txlen, uint8_t *p_rxbuffer, uint8_t
     return ioctl(m_spifd, SPI_IOC_MESSAGE(1), spi_message);
 }
 
-int SPI::write(uint8_t *p_txbuffer,uint8_t p_txlen){
+int SPI::write(uint8_t *p_txbuffer, uint32_t p_txlen){
     struct spi_ioc_transfer spi_message[1];
     memset(spi_message, 0, sizeof(spi_message));
     spi_message[0].tx_buf = (unsigned long)p_txbuffer;
@@ -96,7 +96,7 @@ int SPI::write(uint8_t *p_txbuffer,uint8_t p_txlen){
 
 }
 
-int SPI::read(uint8_t *p_rxbuffer,uint8_t p_rxlen){
+int SPI::read(uint8_t *p_rxbuffer, uint32_t p_rxlen){
     struct spi_ioc_transfer spi_message[1];
     memset(spi_message, 0, sizeof(spi_message));
     
diff --git a/src/spidev_lib++.h b/src/spidev_lib++.h
index 80683fb..c87b422 100644
--- a/src/spidev_lib++.h
+++ b/src/spidev_lib++.h
@@ -53,9 +53,9 @@ bool m_open;
         ~SPI();
         bool begin();
         bool end();
-        int read(uint8_t *p_rxbuffer,uint8_t p_rxlen);
-        int write(uint8_t *p_txbuffer,uint8_t p_txlen);
-        int xfer(uint8_t *p_txbuffer, uint8_t p_txlen, uint8_t *p_rxbuffer, uint8_t p_rxlen);
+        int read(uint8_t *p_rxbuffer, uint32_t p_rxlen);
+        int write(uint8_t *p_txbuffer, uint32_t p_txlen);
+        int xfer(uint8_t *p_txbuffer, uint32_t p_txlen, uint8_t *p_rxbuffer, uint32_t p_rxlen);
         bool setSpeed(uint32_t p_speed);
         bool setMode(uint8_t p_mode);
         bool setBitPerWord(uint8_t p_bit);
diff --git a/src/spidev_lib.c b/src/spidev_lib.c
index 633cf6d..cbde94f 100644
--- a/src/spidev_lib.c
+++ b/src/spidev_lib.c
@@ -77,7 +77,7 @@ int spi_close(int fd) {
     return close(fd);
 }
 
-int spi_xfer(int fd, uint8_t *tx_buffer, uint8_t tx_len, uint8_t *rx_buffer, uint8_t rx_len){
+int spi_xfer(int fd, uint8_t *tx_buffer, uint32_t tx_len, uint8_t *rx_buffer, uint32_t rx_len){
     struct spi_ioc_transfer spi_message[1];
     memset(spi_message, 0, sizeof(spi_message));
     
@@ -88,7 +88,7 @@ int spi_xfer(int fd, uint8_t *tx_buffer, uint8_t tx_len, uint8_t *rx_buffer, uin
     return ioctl(fd, SPI_IOC_MESSAGE(1), spi_message);
 }
 
-int spi_read(int fd, uint8_t *rx_buffer, uint8_t rx_len){
+int spi_read(int fd, uint8_t *rx_buffer, uint32_t rx_len){
     struct spi_ioc_transfer spi_message[1];
     memset(spi_message, 0, sizeof(spi_message));
     
@@ -99,7 +99,7 @@ int spi_read(int fd, uint8_t *rx_buffer, uint8_t rx_len){
     return ioctl(fd, SPI_IOC_MESSAGE(1), spi_message);
 }
 
-int spi_write(int fd, uint8_t *tx_buffer, uint8_t tx_len){
+int spi_write(int fd, uint8_t *tx_buffer, uint32_t tx_len){
     struct spi_ioc_transfer spi_message[1];
     memset(spi_message, 0, sizeof(spi_message));
     
diff --git a/src/spidev_lib.h b/src/spidev_lib.h
index cadc79f..f4b353e 100644
--- a/src/spidev_lib.h
+++ b/src/spidev_lib.h
@@ -39,9 +39,9 @@ typedef struct {
 
 int spi_open(char *device, spi_config_t config);
 int spi_close(int fd);
-int spi_xfer(int fd, uint8_t *tx_buffer, uint8_t tx_len, uint8_t *rx_buffer, uint8_t rx_len);
-int spi_read(int fd, uint8_t *rx_buffer, uint8_t rx_len);
-int spi_write(int fd, uint8_t *tx_buffer, uint8_t tx_len);
+int spi_xfer(int fd, uint8_t *tx_buffer, uint32_t tx_len, uint8_t *rx_buffer, uint32_t rx_len);
+int spi_read(int fd, uint8_t *rx_buffer, uint32_t rx_len);
+int spi_write(int fd, uint8_t *tx_buffer, uint32_t tx_len);
 #ifdef __cplusplus
 }
 #endif