diff --git a/stm32f4/main.c b/stm32f4/main.c
index a2bf8e2..95e8bdd 100755
--- a/stm32f4/main.c
+++ b/stm32f4/main.c
@@ -2,6 +2,7 @@
 #include "led.h"
 // #include "lcd.h"
 #include "rs485.h"
+#include "dwin.h"
 
 volatile uint32_t system_tick_cnt;
 
@@ -31,6 +32,7 @@ void system_init(void)
     system_tick_init();
     // lcd_init();
     rs485_init();
+    dwin_init();
 }
 
 int main(void)
@@ -43,6 +45,7 @@ int main(void)
         led_loop();
         // lcd_loop();
         rs485_loop();
+        dwin_loop();
     }
     return 0;
 }
diff --git a/stm32f4/src/CMakeLists.txt b/stm32f4/src/CMakeLists.txt
index 11a9284..d04ad20 100755
--- a/stm32f4/src/CMakeLists.txt
+++ b/stm32f4/src/CMakeLists.txt
@@ -2,6 +2,7 @@ file(GLOB FILELIST
 led.c
 # lcd.c
 rs485.c
+dwin.c
 )
 
 add_library(src STATIC ${FILELIST})
diff --git a/stm32f4/src/dwin.c b/stm32f4/src/dwin.c
new file mode 100644
index 0000000..ba51256
--- /dev/null
+++ b/stm32f4/src/dwin.c
@@ -0,0 +1,132 @@
+#include "stm32f4xx_rcc.h"
+#include "stm32f4xx_gpio.h"
+#include "stm32f4xx_usart.h"
+#include "stm32f4xx_dma.h"
+#include "dwin.h"
+
+#define DWIN_TX_STREAM   DMA1_Stream6
+#define DWIN_RX_STREAM   DMA1_Stream5
+#define DWIN_BUFF_TX_LEN (4096)
+#define DWIN_BUFF_RX_LEN (4096)
+uint8_t dwin_buff_tx[DWIN_BUFF_TX_LEN] __attribute__((aligned(16)));
+uint8_t dwin_buff_rx[DWIN_BUFF_RX_LEN] __attribute__((aligned(16)));
+
+extern uint32_t system_tick_cnt;
+
+void dwin_init(void)
+{
+    GPIO_InitTypeDef  GPIO_InitStructure;
+    USART_InitTypeDef USART_InitStructure;
+    DMA_InitTypeDef  DMA_InitStructure;
+    NVIC_InitTypeDef NVIC_InitStructure;
+
+    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
+    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);
+    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1, ENABLE);
+
+    GPIO_PinAFConfig(DWIN_PORT, GPIO_PinSource2, GPIO_AF_USART2);
+    GPIO_PinAFConfig(DWIN_PORT, GPIO_PinSource3, GPIO_AF_USART2);
+    GPIO_InitStructure.GPIO_Pin = DWIN_PIN_TX | DWIN_PIN_RX;
+    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
+    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
+    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
+    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
+    GPIO_Init(DWIN_PORT, &GPIO_InitStructure);
+
+    USART_DeInit(USART2);
+    USART_OverSampling8Cmd(USART2, ENABLE);
+    USART_InitStructure.USART_BaudRate = DWIN_BAUDRATE;
+    USART_InitStructure.USART_WordLength = USART_WordLength_8b;
+    USART_InitStructure.USART_Parity = USART_Parity_No;
+    USART_InitStructure.USART_StopBits = USART_StopBits_1;
+    USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
+    USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
+    USART_Init(USART2, &USART_InitStructure);
+    USART_DMACmd(USART2, USART_DMAReq_Tx, ENABLE);
+    USART_DMACmd(USART2, USART_DMAReq_Rx, ENABLE);
+    USART_Cmd(USART2, ENABLE);
+
+    DMA_InitStructure.DMA_BufferSize = DWIN_BUFF_TX_LEN;
+    DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;
+    DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_1QuarterFull;
+    DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
+    DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
+    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
+    DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
+    DMA_InitStructure.DMA_PeripheralBaseAddr =(uint32_t)(&(USART2->DR));
+    DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
+    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
+    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
+    DMA_InitStructure.DMA_Priority = DMA_Priority_Low;
+    DMA_InitStructure.DMA_Channel = DMA_Channel_4;
+    DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;
+    DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)dwin_buff_tx;
+    DMA_Init(DWIN_TX_STREAM, &DMA_InitStructure);
+    /* Configure DMA controller to manage USART RX request */ 
+    DMA_InitStructure.DMA_BufferSize = DWIN_BUFF_RX_LEN;
+    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;
+    DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)dwin_buff_rx;
+    DMA_Init(DWIN_RX_STREAM, &DMA_InitStructure);
+    /* Configure interrupt for USART2 RX */
+    NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn;
+    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 12;
+    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
+    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
+    NVIC_Init(&NVIC_InitStructure);
+    USART_ITConfig(USART2, USART_IT_IDLE, ENABLE);
+    USART_ITConfig(USART2, USART_IT_TC, ENABLE);
+    /* clear IT flag */
+    USART_GetITStatus(USART2, USART_IT_IDLE);
+    USART_ReceiveData(USART2);
+    USART_ClearITPendingBit(USART2, USART_IT_IDLE);
+    USART_ClearITPendingBit(USART2, USART_IT_TC);
+
+    dwin_send(5);
+}
+
+void dwin_send(uint16_t len)
+{
+    DMA_SetCurrDataCounter(DWIN_TX_STREAM, len);
+    DMA_Cmd(DWIN_TX_STREAM, ENABLE);
+}
+
+void dwin_loop(void)
+{
+    static uint32_t ms = 0;
+
+    if (system_tick_cnt < (ms + 500)) {
+        return;
+    }
+    ms = system_tick_cnt;
+}
+
+void USART2_IRQHandler(void)
+{
+    uint16_t len;
+
+    if (USART_GetITStatus(USART2, USART_IT_TC) != RESET)
+    {
+        USART_ClearITPendingBit(USART2, USART_IT_TC);
+        DMA_ClearFlag(DWIN_TX_STREAM, DMA_FLAG_TCIF6 | DMA_FLAG_HTIF6 | DMA_FLAG_TEIF6 | DMA_FLAG_DMEIF6 | DMA_FLAG_FEIF6);
+        DMA_Cmd(DWIN_TX_STREAM, DISABLE);
+        /* after tx complete, config rx */
+        USART_ReceiveData(USART2);
+        USART_ClearITPendingBit(USART2, USART_IT_IDLE);
+        DMA_SetCurrDataCounter(DWIN_RX_STREAM, DWIN_BUFF_RX_LEN);
+        DMA_Cmd(DWIN_RX_STREAM, ENABLE);
+        USART_ITConfig(USART2, USART_IT_IDLE, ENABLE);
+    }
+    if (USART_GetITStatus(USART2, USART_IT_IDLE) != RESET) {
+        USART_ITConfig(USART2, USART_IT_IDLE, DISABLE);
+        USART_ReceiveData(USART2);
+        USART_ClearITPendingBit(USART2, USART_IT_IDLE);
+        DMA_Cmd(DWIN_RX_STREAM, DISABLE);
+        DMA_ClearFlag(DWIN_RX_STREAM, DMA_FLAG_TCIF5 | DMA_FLAG_HTIF5 | DMA_FLAG_TEIF5 | DMA_FLAG_DMEIF5 | DMA_FLAG_FEIF5);
+        len = DMA_GetCurrDataCounter(DWIN_RX_STREAM);
+        len = DWIN_BUFF_RX_LEN - len;
+        for (uint16_t i = 0; i < len; i++) {
+            dwin_buff_tx[i] = dwin_buff_rx[i] + 1;
+        }
+        dwin_send(len);
+    }
+}
diff --git a/stm32f4/src/dwin.h b/stm32f4/src/dwin.h
new file mode 100644
index 0000000..86c5353
--- /dev/null
+++ b/stm32f4/src/dwin.h
@@ -0,0 +1,57 @@
+#ifndef __RS485_H__
+#define __RS485_H__
+
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+#include "stm32f4xx.h"
+
+#define DWIN_PORT      (GPIOA)
+#define DWIN_PIN_TX    (GPIO_Pin_2)
+#define DWIN_PIN_RX    (GPIO_Pin_3)
+#define DWIN_BAUDRATE  (115200)
+
+struct dwin_ctrl_s {
+    uint32_t baudrate;
+    uint32_t cali_conc;
+    uint8_t cali_active;
+    uint8_t cali_restore;
+    uint8_t mb_addr;
+};
+
+struct dwin_info_s {
+    uint8_t gas_name[16];
+    uint8_t sn[16];
+    uint32_t concentration;
+    uint8_t conc_unit[16];
+    uint32_t det_temp;
+    uint32_t sig_cts;
+    uint32_t ref_cts;
+    uint32_t air_pressure;
+    uint32_t range;
+    uint32_t mini_cali;
+    uint16_t sts_zero;
+    uint16_t sts_span;
+    uint16_t sts_active;
+    uint16_t sts_restore;
+    uint16_t cali_zero_enable;
+    uint16_t cali_zero_temp;
+    uint32_t cali_zero_sig;
+    uint32_t cali_zero_ref;
+    uint16_t cali_span_enable;
+    uint16_t cali_span_temp;
+    uint32_t cali_span_conc;
+    uint32_t cali_span_sig;
+    uint32_t cali_span_ref;
+};
+
+void dwin485_init(void);
+void dwin_send(uint16_t len);
+void dwin_loop(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __RS485_H__ */
diff --git a/stm32f4/src/rs485.c b/stm32f4/src/rs485.c
index e7c0a94..84e9148 100644
--- a/stm32f4/src/rs485.c
+++ b/stm32f4/src/rs485.c
@@ -7,7 +7,7 @@
 #define RS485_TX_STREAM   DMA1_Stream3
 #define RS485_RX_STREAM   DMA1_Stream1
 #define RS485_BUFF_TX_LEN (4096)
-#define RS485_BUFF_RX_LEN (1024)
+#define RS485_BUFF_RX_LEN (4096)
 uint8_t rs485_buff_tx[RS485_BUFF_TX_LEN] __attribute__((aligned(16)));
 uint8_t rs485_buff_rx[RS485_BUFF_RX_LEN] __attribute__((aligned(16)));
 
@@ -99,7 +99,7 @@ void rs485_init(void)
     USART_ClearITPendingBit(USART3, USART_IT_IDLE);
     USART_ClearITPendingBit(USART3, USART_IT_TC);
 
-    rs485_send(15);
+    // rs485_send(15);
 }
 
 void rs485_send(uint16_t len)
@@ -109,6 +109,16 @@ void rs485_send(uint16_t len)
     DMA_Cmd(RS485_TX_STREAM, ENABLE);
 }
 
+void modbus_get_sn(void)
+{
+
+}
+
+void modbus_get_info(void)
+{
+
+}
+
 void rs485_loop(void)
 {
     static uint32_t ms = 0;