title: STM32+FreeRTOS issue when using “HAL_UART_TRANSMIT_IT”
body: <p>We want our device (STM32-F446RE running FreeRTOS + Telit ME310G1 modem) to communicate to the AWS cloud. We are trying to follow the Cellular Interface Library Demo, in particular following this- <a href="https://i.stack.imgur.com/PGse9.png" rel="nofollow noreferrer">diagram</a></p>
  <p>We are using coreMQTT Agent, MbedTLS libraries, <a href="https://github.com/aws/amazon-freertos/blob/feature/cellular/vendors/st/boards/stm32l475_discovery/ports/comm_if/comm_if_uart.c" rel="nofollow noreferrer">the amazon communication interface implementation for UART</a> and <a href="https://github.com/aws/amazon-freertos/blob/feature/cellular/vendors/st/boards/stm32l475_discovery/ports/common_io/iot_uart.c" rel="nofollow noreferrer">amazon UART API implementation</a>.</p>
  <p>UART using 115200 baud rate.</p>
  <p>Currently failing on the Cellular_Init function when trying to send the first AT command to the modem, specifically when calling the HAL_UART_TRANSMIT_IT function from the above comm interface send function. While debugging we see that the USART1_IRQHandler is called infinite times and nothing is sent through the UART communication.
  We are using the default handler, do we need to implement it in any way?</p>
  <pre><code>void USART1_IRQHandler(void)
  {
    HAL_UART_IRQHandler(&amp;huart1);
  }
  </code></pre>
  <p>Any help will be appreciated.</p>
  <p>Thanks in advance,
  Guy</p>