diff --git a/examples/stm32/CMakeLists.txt b/examples/stm32/CMakeLists.txt
index cd98033..775344e 100644
--- a/examples/stm32/CMakeLists.txt
+++ b/examples/stm32/CMakeLists.txt
@@ -13,20 +13,6 @@ set(CMAKE_TOOLCHAIN_FILE ${stm32_cmake_SOURCE_DIR}/cmake/stm32_gcc.cmake)
 project(${PROJ_NAME} CXX C ASM)
 set(CMAKE_INCLUDE_CURRENT_DIR TRUE)
 
-set(TARGET_NAME ${PROJ_NAME})
-
-add_executable(${TARGET_NAME} 
-    main.c 
-    bsp/blackpill/blackpill.c
-    nmbs/port.c
-    )
-
-target_include_directories(
-    ${TARGET_NAME} PRIVATE
-    ${CMAKE_CURRENT_SOURCE_DIR}/bsp
-    ${CMAKE_CURRENT_SOURCE_DIR}/nmbs
-)
-
 stm32_fetch_cmsis(F4)
 stm32_fetch_hal(F4)
 
@@ -81,30 +67,60 @@ endif()
 add_library(nanomodbus ${nanomodbus_SOURCE_DIR}/nanomodbus.c)
 target_include_directories(nanomodbus PUBLIC ${nanomodbus_SOURCE_DIR})
 
-target_link_libraries(
-    ${TARGET_NAME} 
-    STM32::NoSys 
-    CMSIS::STM32::F401CC
-    HAL::STM32::F4::CORTEX
-    HAL::STM32::F4::RCC
-    HAL::STM32::F4::PWR
-    HAL::STM32::F4::GPIO
-    HAL::STM32::F4::TIM
-    HAL::STM32::F4::UART
-    HAL::STM32::F4::USART
-    HAL::STM32::F4::SPI
-    HAL::STM32::F4::DMA
-    wizchip
-    freertos_kernel
-    nanomodbus
-)
+set(TARGET_NAMES modbus_rtu modbus_tcp)
 
-add_custom_command(TARGET ${TARGET_NAME} POST_BUILD
-    COMMAND ${CMAKE_SIZE} $<TARGET_FILE:${TARGET_NAME}>
-)
-add_custom_command(TARGET ${TARGET_NAME} POST_BUILD
-COMMAND ${CMAKE_OBJCOPY} -O ihex $<TARGET_FILE:${TARGET_NAME}> ${TARGET_NAME}.hex
-)
-add_custom_command(TARGET ${TARGET_NAME} POST_BUILD
-COMMAND ${CMAKE_OBJCOPY} -O binary $<TARGET_FILE:${TARGET_NAME}> ${TARGET_NAME}.bin
-)
\ No newline at end of file
+foreach(TARGET_NAME ${TARGET_NAMES})
+
+  add_executable(${TARGET_NAME} 
+      ${TARGET_NAME}.c 
+      bsp/blackpill/blackpill.c
+      nmbs/port.c
+      )
+
+  target_include_directories(
+      ${TARGET_NAME} PRIVATE
+      ${CMAKE_CURRENT_SOURCE_DIR}/bsp
+      ${CMAKE_CURRENT_SOURCE_DIR}/nmbs
+  )
+
+  if(${TARGET_NAME} STREQUAL "modbus_rtu")
+    target_compile_definitions(
+        ${TARGET_NAME} PRIVATE
+        NMBS_RTU
+    )
+  elseif(${TARGET_NAME} STREQUAL "modbus_tcp")
+    target_compile_definitions(
+        ${TARGET_NAME} PRIVATE
+        NMBS_TCP
+    )
+  endif()
+
+  target_link_libraries(
+      ${TARGET_NAME} 
+      STM32::NoSys 
+      CMSIS::STM32::F401CC
+      HAL::STM32::F4::CORTEX
+      HAL::STM32::F4::RCC
+      HAL::STM32::F4::PWR
+      HAL::STM32::F4::GPIO
+      HAL::STM32::F4::TIM
+      HAL::STM32::F4::UART
+      HAL::STM32::F4::USART
+      HAL::STM32::F4::SPI
+      HAL::STM32::F4::DMA
+      wizchip
+      freertos_kernel
+      nanomodbus
+  )
+
+  add_custom_command(TARGET ${TARGET_NAME} POST_BUILD
+      COMMAND ${CMAKE_SIZE} $<TARGET_FILE:${TARGET_NAME}>
+  )
+  add_custom_command(TARGET ${TARGET_NAME} POST_BUILD
+  COMMAND ${CMAKE_OBJCOPY} -O ihex $<TARGET_FILE:${TARGET_NAME}> ${TARGET_NAME}.hex
+  )
+  add_custom_command(TARGET ${TARGET_NAME} POST_BUILD
+  COMMAND ${CMAKE_OBJCOPY} -O binary $<TARGET_FILE:${TARGET_NAME}> ${TARGET_NAME}.bin
+  )
+
+endforeach()
\ No newline at end of file
diff --git a/examples/stm32/modbus_rtu.c b/examples/stm32/modbus_rtu.c
new file mode 100644
index 0000000..de9472c
--- /dev/null
+++ b/examples/stm32/modbus_rtu.c
@@ -0,0 +1,77 @@
+#include "blackpill/blackpill.h"
+#include "nanomodbus.h"
+#include "nmbs/port.h"
+
+#include "FreeRTOS.h"
+#include "task.h"
+
+#define TEST_SERVER 1
+#define TEST_CLIENT 0
+
+static void blink(void* args);
+static void modbus(void* args);
+
+uint32_t HAL_GetTick(void)
+{
+    return xTaskGetTickCount();
+}
+
+int main(void)
+{
+    BSP_Init();
+
+    xTaskCreate(blink,  "blink",  128,      NULL, 4, NULL);
+    xTaskCreate(modbus, "modbus", 128 * 16, NULL, 2, NULL);
+
+    vTaskStartScheduler();
+
+    for(;;){}
+}
+
+static void blink(void* args)
+{
+    for(;;)
+    {
+        HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_SET);
+        vTaskDelay(500);
+        HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_RESET);
+        vTaskDelay(500);
+    }
+}
+
+nmbs_t nmbs;
+nmbs_server_t nmbs_server = 
+{
+  .id = 0x01,
+  .coils = {0,},
+  .regs  = {0,},
+};
+
+static void modbus(void* args)
+{
+#if TEST_SERVER
+    nmbs_server_init(&nmbs, &nmbs_server);
+#endif
+
+#if TEST_CLIENT
+    uint8_t coils_test[32];
+    uint16_t regs_test[32];
+    nmbs_client_init(&nmbs);
+#endif
+
+    for(;;){
+#if TEST_SERVER
+        nmbs_server_poll(&nmbs);
+        taskYIELD();
+#endif
+#if TEST_CLIENT
+        nmbs_set_destination_rtu_address(&nmbs, 0x01);
+        nmbs_error status = nmbs_read_holding_registers(&nmbs, 0, 32, regs_test);
+        status = nmbs_write_multiple_registers(&nmbs, 0, 32, regs_test);
+        if(status != NMBS_ERROR_NONE)
+        {
+        while(true){}
+        }
+#endif
+    }
+}
diff --git a/examples/stm32/main.c b/examples/stm32/modbus_tcp.c
similarity index 99%
rename from examples/stm32/main.c
rename to examples/stm32/modbus_tcp.c
index 13e5211..74f84be 100644
--- a/examples/stm32/main.c
+++ b/examples/stm32/modbus_tcp.c
@@ -76,7 +76,6 @@ int main(void)
     }
 }
 
-
 static void blink(void* args)
 {
     for(;;)
diff --git a/examples/stm32/nmbs/port.c b/examples/stm32/nmbs/port.c
index cb85834..15e0fe0 100644
--- a/examples/stm32/nmbs/port.c
+++ b/examples/stm32/nmbs/port.c
@@ -197,4 +197,31 @@ int32_t write_socket(const uint8_t *buf, uint16_t count, int32_t byte_timeout_ms
 {
     return send(MB_SOCKET, buf, count);
 }
+#endif
+
+#ifdef NMBS_RTU
+static int32_t read_serial(uint8_t* buf, uint16_t count, int32_t byte_timeout_ms, void* arg)
+{
+    HAL_StatusTypeDef status = HAL_UART_Receive(&MB_UART, buf, count, byte_timeout_ms);
+    if(status == HAL_OK)
+    {
+        return count;
+    }
+    else
+    {
+        return 0;
+    }
+}
+static int32_t write_serial(const uint8_t* buf, uint16_t count, int32_t byte_timeout_ms, void* arg)
+{
+    HAL_StatusTypeDef status = HAL_UART_Transmit(&MB_UART, buf, count, byte_timeout_ms);
+    if(status == HAL_OK)
+    {
+        return count;
+    }
+    else
+    {
+        return 0;
+    }
+}
 #endif
\ No newline at end of file
diff --git a/examples/stm32/nmbs/port.h b/examples/stm32/nmbs/port.h
index e122186..ca80e23 100644
--- a/examples/stm32/nmbs/port.h
+++ b/examples/stm32/nmbs/port.h
@@ -23,6 +23,7 @@ extern "C" {
 // modbus rtu
 #define MB_UART huart1
 #define RX_BUF_SIZE 256
+extern UART_HandleTypeDef MB_UART;
 #endif
 
 typedef struct tNmbsServer{