diff --git a/STM32_CO2_NODE/Core/Src/uart_callbacks.cpp b/STM32_CO2_NODE/Core/Src/uart_callbacks.cpp
new file mode 100644
index 0000000..0ec1de7
--- /dev/null
+++ b/STM32_CO2_NODE/Core/Src/uart_callbacks.cpp
@@ -0,0 +1,25 @@
+#include "FreeRTOS.h"
+#include "task.h"
+#include "semphr.h"
+
+#include "usart.h"
+
+#include "mhz19c.hpp"
+
+extern MHZ19C* g_mhz19c;
+
+extern "C"
+void HAL_UART_RxCpltCallback(
+    UART_HandleTypeDef* huart)
+{
+    extern UART_HandleTypeDef huart1;
+
+    if(huart == &huart1)
+    {
+        BaseType_t hpw = pdFALSE;
+
+        xSemaphoreGiveFromISR( g_mhz19c->GetRxSemaphore(), &hpw);
+
+        portYIELD_FROM_ISR(hpw);
+    }
+}
diff --git a/STM32_CO2_NODE/Drivers/MHZ19C/mhz19c.cpp b/STM32_CO2_NODE/Drivers/MHZ19C/mhz19c.cpp
index 5ce2d65..f52e531 100644
--- a/STM32_CO2_NODE/Drivers/MHZ19C/mhz19c.cpp
+++ b/STM32_CO2_NODE/Drivers/MHZ19C/mhz19c.cpp
@@ -3,6 +3,8 @@
 MHZ19C::MHZ19C(UART_HandleTypeDef* huart)
     : uart(huart)
 {
+	rxDoneSem = xSemaphoreCreateBinary();
+
     BuildReadFrame();
 }
 
@@ -33,22 +35,11 @@ uint8_t MHZ19C::Checksum(uint8_t* data)
 
 bool MHZ19C::ReadCO2(uint16_t& ppm)
 {
-    if(HAL_UART_Transmit(
-            uart,
-            txFrame,
-            9,
-            100)
-       != HAL_OK)
-    {
-        return false;
-    }
+    HAL_UART_Transmit(uart, txFrame, 9, 100);
 
-    if(HAL_UART_Receive(
-            uart,
-            rxFrame,
-            9,
-            100)
-       != HAL_OK)
+    HAL_UART_Receive_DMA(uart, rxFrame, 9);
+
+    if(xSemaphoreTake(rxDoneSem, pdMS_TO_TICKS(200)) != pdTRUE)
     {
         return false;
     }
@@ -58,9 +49,7 @@ bool MHZ19C::ReadCO2(uint16_t& ppm)
         return false;
     }
 
-    ppm =
-        (rxFrame[2] << 8) |
-        rxFrame[3];
+    ppm = (rxFrame[2] << 8) | rxFrame[3];
 
     return true;
 }
@@ -82,10 +71,5 @@ void MHZ19C::CalibrateZero()
 
     cmd[8] = Checksum(cmd);
 
-    HAL_UART_Transmit(
-        uart,
-        cmd,
-        9,
-        100
-    );
+    HAL_UART_Transmit(uart, cmd, 9, 100);
 }
diff --git a/STM32_CO2_NODE/Drivers/MHZ19C/mhz19c.hpp b/STM32_CO2_NODE/Drivers/MHZ19C/mhz19c.hpp
index 09022cd..b469c23 100644
--- a/STM32_CO2_NODE/Drivers/MHZ19C/mhz19c.hpp
+++ b/STM32_CO2_NODE/Drivers/MHZ19C/mhz19c.hpp
@@ -1,7 +1,8 @@
 #pragma once
 
 #include "stm32f1xx_hal.h"
-
+#include "FreeRTOS.h"
+#include "semphr.h"
 #include <cstdint>
 
 class MHZ19C
@@ -14,6 +15,11 @@ public:
 
     void CalibrateZero();
 
+    SemaphoreHandle_t GetRxSemaphore()
+    {
+        return rxDoneSem;
+    }
+
 private:
 
     UART_HandleTypeDef* uart;
@@ -21,6 +27,8 @@ private:
     uint8_t txFrame[9];
     uint8_t rxFrame[9];
 
+    SemaphoreHandle_t rxDoneSem;
+
     void BuildReadFrame();
 
     uint8_t Checksum(uint8_t* data);
diff --git a/STM32_CO2_NODE/Drivers/SDCard/sdcard.cpp b/STM32_CO2_NODE/Drivers/SDCard/sdcard.cpp
index 3dc88c7..41c801b 100644
--- a/STM32_CO2_NODE/Drivers/SDCard/sdcard.cpp
+++ b/STM32_CO2_NODE/Drivers/SDCard/sdcard.cpp
@@ -8,40 +8,25 @@ extern "C"
 
 bool SDCard::Init()
 {
-    FATFS fs;
-
     return f_mount(&fs, "", 1) == FR_OK;
 }
 
-bool SDCard::AppendCO2(uint32_t timestamp,
-                       uint16_t ppm)
+bool SDCard::AppendCO2(uint32_t timestamp, uint16_t ppm)
 {
     FIL file;
 
-    if (f_open(
-            &file,
-            "co2_log.csv",
-            FA_OPEN_APPEND | FA_WRITE) != FR_OK)
+    if (f_open(&file, "co2_log.csv", FA_OPEN_APPEND | FA_WRITE) != FR_OK)
     {
         return false;
     }
 
     char buffer[64];
 
-    int len = snprintf(
-        buffer,
-        sizeof(buffer),
-        "%lu,%u\r\n",
-        timestamp,
-        ppm);
+    int len = snprintf(buffer, sizeof(buffer), "%lu,%u\r\n", timestamp, ppm);
 
     UINT written;
 
-    f_write(
-        &file,
-        buffer,
-        len,
-        &written);
+    f_write( &file, buffer, len, &written);
 
     f_close(&file);
 
diff --git a/STM32_CO2_NODE/Drivers/SDCard/sdcard.hpp b/STM32_CO2_NODE/Drivers/SDCard/sdcard.hpp
index 319157e..e709d02 100644
--- a/STM32_CO2_NODE/Drivers/SDCard/sdcard.hpp
+++ b/STM32_CO2_NODE/Drivers/SDCard/sdcard.hpp
@@ -2,12 +2,20 @@
 
 #include <cstdint>
 
+extern "C"
+{
+#include "ff.h"
+}
+
 class SDCard
 {
 public:
 
     bool Init();
 
-    bool AppendCO2(uint32_t timestamp,
-                   uint16_t ppm);
+    bool AppendCO2(uint32_t timestamp, uint16_t ppm);
+
+private:
+
+    FATFS fs;
 };
diff --git a/STM32_CO2_NODE/FATFS/App/Tasks/can_task.cpp b/STM32_CO2_NODE/FATFS/App/Tasks/can_task.cpp
index 2491a9a..a73432b 100644
--- a/STM32_CO2_NODE/FATFS/App/Tasks/can_task.cpp
+++ b/STM32_CO2_NODE/FATFS/App/Tasks/can_task.cpp
@@ -17,14 +17,8 @@ void CANTask_RunOnce()
 {
     CO2Data data;
 
-    if(xQueueReceive(
-           g_canQueue,
-           &data,
-           pdMS_TO_TICKS(100))
-       == pdTRUE)
+    if(xQueueReceive(g_canQueue, &data, pdMS_TO_TICKS(100)) == pdTRUE)
     {
-        canProtocol.sendCO2(
-            data.ppm
-        );
+        canProtocol.sendCO2(data.ppm);
     }
 }
diff --git a/STM32_CO2_NODE/FATFS/App/Tasks/co2_task.cpp b/STM32_CO2_NODE/FATFS/App/Tasks/co2_task.cpp
index ddb8d53..631d618 100644
--- a/STM32_CO2_NODE/FATFS/App/Tasks/co2_task.cpp
+++ b/STM32_CO2_NODE/FATFS/App/Tasks/co2_task.cpp
@@ -14,6 +14,8 @@ extern UART_HandleTypeDef huart1;
 
 static MHZ19C sensor(&huart1);
 
+MHZ19C* g_mhz19c = &sensor;
+
 void CO2Task_RunOnce()
 {
     CO2Data data;
diff --git a/STM32_CO2_NODE/FATFS/App/Tasks/sd_task.cpp b/STM32_CO2_NODE/FATFS/App/Tasks/sd_task.cpp
index ce3d576..079b1ed 100644
--- a/STM32_CO2_NODE/FATFS/App/Tasks/sd_task.cpp
+++ b/STM32_CO2_NODE/FATFS/App/Tasks/sd_task.cpp
@@ -12,20 +12,11 @@ void SDTask_RunOnce()
 {
     CO2Data data;
 
-    if(xQueueReceive(
-            g_sdQueue,
-            &data,
-            pdMS_TO_TICKS(100))
-       == pdTRUE)
+    if(xQueueReceive(g_sdQueue, &data, pdMS_TO_TICKS(100)) == pdTRUE)
     {
         char line[64];
 
-        sprintf(
-            line,
-            "CO2:%u t:%lu\r\n",
-            data.ppm,
-            data.timestamp
-        );
+        sprintf(line, "CO2:%u t:%lu\r\n", data.ppm, data.timestamp);
 
         sd.write(line);
     }