EC20 4G模块可以通过串口和USB去驱动，但是串口速度比较慢，所以通过USB驱动才能提高通信速率。

硬件连接:
STM32F407:



EC20模块：



部分参考代码：

1. 
   
2. /* USER CODE END Header */
   
3. /* Includes ------------------------------------------------------------------*/
   
4. #include "main.h"
   
5. #include "usb_host.h"
   
6. #include "usbh_def.h"
   
7. #include "usbh_cdc.h"
   
8. #include "string.h"
   
9. 
   
10. UART_HandleTypeDef huart1;
    
11. 
    
12. /* USER CODE BEGIN PV */
    
13. 
    
14. /* USER CODE END PV */
    
15. 
    
16. /* Private function prototypes -----------------------------------------------*/
    
17. void SystemClock_Config(void);
    
18. static void MX_GPIO_Init(void);
    
19. static void MX_USART1_UART_Init(void);
    
20. void MX_USB_HOST_Process(void);
    
21. 
    
22. 
    
23. unsigned char recData[100];
    
24. unsigned int recLen;  
    
25. 
    
26. void delay_ums(unsigned int i)
    
27. {
    
28.         unsigned int cnt;
    
29.         while(i--)
    
30.         {
    
31.                 cnt=33500;
    
32.                 while(cnt--);
    
33.         }
    
34. }
    
35. 
    
36. extern USBH_HandleTypeDef hUsbHostFS;
    
37. int main(void)
    
38. {
    
39.         unsigned int a;
    
40.         HAL_Init();
    
41.         SystemClock_Config();
    
42.         MX_GPIO_Init();
    
43.         MX_USART1_UART_Init();
    
44.         MX_USB_HOST_Init();
    
45.         MX_GPIO_Init();
    
46. 
    
47.         HAL_GPIO_WritePin(GPIOC, GPIO_PIN_0, GPIO_PIN_SET);  
    
48. 
    
49.         delay_ums(1000);
    
50.         HAL_GPIO_WritePin(GPIOC, GPIO_PIN_0, GPIO_PIN_RESET);  
    
51. 
    
52.   while (1)
    
53.   {
    
54.     /* USER CODE END WHILE */
    
55.     MX_USB_HOST_Process();
    
56.         delay_ums(1);
    
57.           a++;
    
58.           if(a>1000)
    
59.           {
    
60.                   a=0;
    
61.                   USBH_CDC_Transmit(&hUsbHostFS, "AT\r\n", strlen("AT\r\n"));
    
62.           }
    
63.     /* USER CODE BEGIN 3 */
    
64.   }
    
65.   /* USER CODE END 3 */
    
66. }
    
67. 
    
68. /**
    
69.   * @brief System Clock Configuration
    
70.   * @retval None
    
71.   */
    
72. void SystemClock_Config(void)
    
73. {
    
74.   RCC_OscInitTypeDef RCC_OscInitStruct = {0};
    
75.   RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
    
76. 
    
77.   /** Configure the main internal regulator output voltage
    
78.   */
    
79.   __HAL_RCC_PWR_CLK_ENABLE();
    
80.   __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
    
81.   /** Initializes the RCC Oscillators according to the specified parameters
    
82.   * in the RCC_OscInitTypeDef structure.
    
83.   */
    
84.   RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
    
85.   RCC_OscInitStruct.HSEState = RCC_HSE_ON;
    
86.   RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
    
87.   RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
    
88.   RCC_OscInitStruct.PLL.PLLM = 4;
    
89.   RCC_OscInitStruct.PLL.PLLN = 168;
    
90.   RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
    
91.   RCC_OscInitStruct.PLL.PLLQ = 7;
    
92.   if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
    
93.   {
    
94.     Error_Handler();
    
95.   }
    
96.   /** Initializes the CPU, AHB and APB buses clocks
    
97.   */
    
98.   RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
    
99.                               |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
    
100.   RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
     
101.   RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
     
102.   RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
     
103.   RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;
     
104. 
     
105.   if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK)
     
106.   {
     
107.     Error_Handler();
     
108.   }
     
109. }
     
110. 
     
111. /**
     
112.   * @brief USART1 Initialization Function
     
113.   * @param None
     
114.   * @retval None
     
115.   */
     
116. static void MX_USART1_UART_Init(void)
     
117. {
     
118. 
     
119.   /* USER CODE BEGIN USART1_Init 0 */
     
120. 
     
121.   /* USER CODE END USART1_Init 0 */
     
122. 
     
123.   /* USER CODE BEGIN USART1_Init 1 */
     
124. 
     
125.   /* USER CODE END USART1_Init 1 */
     
126.   huart1.Instance = USART1;
     
127.   huart1.Init.BaudRate = 115200;
     
128.   huart1.Init.WordLength = UART_WORDLENGTH_8B;
     
129.   huart1.Init.StopBits = UART_STOPBITS_1;
     
130.   huart1.Init.Parity = UART_PARITY_NONE;
     
131.   huart1.Init.Mode = UART_MODE_TX_RX;
     
132.   huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
     
133.   huart1.Init.OverSampling = UART_OVERSAMPLING_16;
     
134.   if (HAL_UART_Init(&huart1) != HAL_OK)
     
135.   {
     
136.     Error_Handler();
     
137.   }
     
138.   /* USER CODE BEGIN USART1_Init 2 */
     
139. 
     
140.   /* USER CODE END USART1_Init 2 */
     
141. 
     
142. }
     
143. 
     
144. /**
     
145.   * @brief GPIO Initialization Function
     
146.   * @param None
     
147.   * @retval None
     
148.   */
     
149. static void MX_GPIO_Init(void)
     
150. {
     
151.   GPIO_InitTypeDef GPIO_InitStruct = {0};
     
152. 
     
153.         /* GPIO Ports Clock Enable */
     
154.         __HAL_RCC_GPIOH_CLK_ENABLE();
     
155.         __HAL_RCC_GPIOA_CLK_ENABLE();
     
156.         __HAL_RCC_GPIOC_CLK_ENABLE();
     
157.   /*Configure GPIO pin Output Level */
     
158. 
     
159. 
     
160.   /*Configure GPIO pin : PA15 */
     
161.   GPIO_InitStruct.Pin = GPIO_PIN_15;
     
162.   GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
     
163.   GPIO_InitStruct.Pull = GPIO_NOPULL;
     
164.   GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
     
165.   HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
     
166.   HAL_GPIO_WritePin(GPIOA, GPIO_PIN_15, GPIO_PIN_SET);
     
167. 
     
168. 
     
169. 
     
170.   /*Configure GPIO pin : PA15 */
     
171.   GPIO_InitStruct.Pin = GPIO_PIN_0|GPIO_PIN_2;
     
172.   GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
     
173.   GPIO_InitStruct.Pull = GPIO_NOPULL;
     
174.   GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
     
175.   HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
     
176.   HAL_GPIO_WritePin(GPIOC, GPIO_PIN_0|GPIO_PIN_2, GPIO_PIN_RESET);  
     
177. }
     
178. 
     
179. /* USER CODE BEGIN 4 */
     
180. 
     
181. /* USER CODE END 4 */
     
182. 
     
183. /**
     
184.   * @brief  This function is executed in case of error occurrence.
     
185.   * @retval None
     
186.   */
     
187. void Error_Handler(void)
     
188. {
     
189.   /* USER CODE BEGIN Error_Handler_Debug */
     
190.   /* User can add his own implementation to report the HAL error return state */
     
191. 
     
192.   /* USER CODE END Error_Handler_Debug */
     
193. }
     
194. 
     
195. #ifdef  USE_FULL_ASSERT
     
196. /**
     
197.   * @brief  Reports the name of the source file and the source line number
     
198.   *         where the assert_param error has occurred.
     
199.   * @param  file: pointer to the source file name
     
200.   * @param  line: assert_param error line source number
     
201.   * @retval None
     
202.   */
     
203. void assert_failed(uint8_t *file, uint32_t line)
     
204. {
     
205.   /* USER CODE BEGIN 6 */
     
206.   /* User can add his own implementation to report the file name and line number,
     
207.      tex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
     
208.   /* USER CODE END 6 */
     
209. }
     
210. #endif /* USE_FULL_ASSERT */
     
211. 
     
212. /************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
     
213. void USBH_CDC_ReceiveCallback(USBH_HandleTypeDef *phost)
     
214. {
     
215.         recLen = USBH_CDC_GetLastReceivedDataSize(phost);
     
216.         
     
217.         HAL_UART_Transmit_IT(&huart1 ,(uint8_t*)recData,recLen);
     
218.         while(__HAL_UART_GET_FLAG(&huart1,UART_FLAG_TC)!=SET);                //等待发送结束        
     
219.         
     
220.         memset(recData,0x00,sizeof(recData));
     
221. }
     
222. 
     

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