SPMA087 March   2023 TM4C1230C3PM , TM4C1230C3PM , TM4C1230D5PM , TM4C1230D5PM , TM4C1230E6PM , TM4C1230E6PM , TM4C1230H6PM , TM4C1230H6PM , TM4C1231C3PM , TM4C1231C3PM , TM4C1231D5PM , TM4C1231D5PM , TM4C1231D5PZ , TM4C1231D5PZ , TM4C1231E6PM , TM4C1231E6PM , TM4C1231E6PZ , TM4C1231E6PZ , TM4C1231H6PGE , TM4C1231H6PGE , TM4C1231H6PM , TM4C1231H6PM , TM4C1231H6PZ , TM4C1231H6PZ , TM4C1232C3PM , TM4C1232C3PM , TM4C1232D5PM , TM4C1232D5PM , TM4C1232E6PM , TM4C1232E6PM , TM4C1232H6PM , TM4C1232H6PM , TM4C1233C3PM , TM4C1233C3PM , TM4C1233D5PM , TM4C1233D5PM , TM4C1233D5PZ , TM4C1233D5PZ , TM4C1233E6PM , TM4C1233E6PM , TM4C1233E6PZ , TM4C1233E6PZ , TM4C1233H6PGE , TM4C1233H6PGE , TM4C1233H6PM , TM4C1233H6PM , TM4C1233H6PZ , TM4C1233H6PZ , TM4C1236D5PM , TM4C1236D5PM , TM4C1236E6PM , TM4C1236E6PM , TM4C1236H6PM , TM4C1236H6PM , TM4C1237D5PM , TM4C1237D5PM , TM4C1237D5PZ , TM4C1237D5PZ , TM4C1237E6PM , TM4C1237E6PM , TM4C1237E6PZ , TM4C1237E6PZ , TM4C1237H6PGE , TM4C1237H6PGE , TM4C1237H6PM , TM4C1237H6PM , TM4C1237H6PZ , TM4C1237H6PZ , TM4C123AE6PM , TM4C123AE6PM , TM4C123AH6PM , TM4C123AH6PM , TM4C123BE6PM , TM4C123BE6PM , TM4C123BE6PZ , TM4C123BE6PZ , TM4C123BH6PGE , TM4C123BH6PGE , TM4C123BH6PM , TM4C123BH6PM , TM4C123BH6PZ , TM4C123BH6PZ , TM4C123FE6PM , TM4C123FE6PM , TM4C123FH6PM , TM4C123FH6PM , TM4C123GE6PM , TM4C123GE6PM , TM4C123GE6PZ , TM4C123GE6PZ , TM4C123GH6PGE , TM4C123GH6PGE , TM4C123GH6PM , TM4C123GH6PM , TM4C123GH6PZ , TM4C123GH6PZ , TM4C123GH6ZXR , TM4C123GH6ZXR , TM4C1290NCPDT , TM4C1290NCPDT , TM4C1290NCZAD , TM4C1290NCZAD , TM4C1292NCPDT , TM4C1292NCPDT , TM4C1292NCZAD , TM4C1292NCZAD , TM4C1294KCPDT , TM4C1294KCPDT , TM4C1294NCPDT , TM4C1294NCPDT , TM4C1294NCZAD , TM4C1294NCZAD , TM4C1297NCZAD , TM4C1297NCZAD , TM4C1299KCZAD , TM4C1299KCZAD , TM4C1299NCZAD , TM4C1299NCZAD , TM4C129CNCPDT , TM4C129CNCPDT , TM4C129CNCZAD , TM4C129CNCZAD , TM4C129DNCPDT , TM4C129DNCPDT , TM4C129DNCZAD , TM4C129DNCZAD , TM4C129EKCPDT , TM4C129EKCPDT , TM4C129ENCPDT , TM4C129ENCPDT , TM4C129ENCZAD , TM4C129ENCZAD , TM4C129LNCZAD , TM4C129LNCZAD , TM4C129XKCZAD , TM4C129XKCZAD , TM4C129XNCZAD , TM4C129XNCZAD

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2How to Install
    1. 2.1 Update the FreeRTOS Version in the TivaWare Directory
    2. 2.2 Adding FreeRTOS Hardware Driver Files for TM4C LaunchPads
  5. 3Architecture for TM4C FreeRTOS Examples
    1. 3.1 Proper Clock Configuration
    2. 3.2 How to use Hardware Interrupts Alongside the FreeRTOS Kernel
    3. 3.3 Code Composer Studio Debug Support for FreeRTOS
  6. 4Example Project Walkthroughs
    1. 4.1 Download and Import the Examples
    2. 4.2 USB Examples
      1. 4.2.1 usb_dev_bulk
      2. 4.2.2 usb_dev_cdcserial
      3. 4.2.3 usb_dev_keyboard
    3. 4.3 Ethernet Examples
      1. 4.3.1 enet_lwip
        1. 4.3.1.1 Running enet_lwip Example
      2. 4.3.2 enet_io
        1. 4.3.2.1 Running enet_io Example
  7. 5References

4.2.3 usb_dev_keyboard

This example showcases how to configure the USB peripheral to function in USB HID device mode while enumerating the HID device as a USB keyboard peripheral. By enumerating as a keyboard, it is possible for the microcontroller to type out text on the screen exactly like a user writing on a keyboard. The messages that are typed out are controlled by the push buttons on the LaunchPad. One button will always output a default greeting message. The other can print out a second default message that can be updated by sending a new message to the Stellaris Virtual COM Port with a COM port terminal. The message must be appended with a CR-LF to be recognized as completed. The message size is limited to 255 bytes by default and sending a message longer than 255 bytes will result in the message being broken up. The default size can be increased in the project by editing the UART_BUFFER_SIZE variable. If three or more messages are sent sequentially without printing any messages out, only the first two will be stored for display.

In this example, two tasks are created. The first task manages updating the dynamic message by receiving data over UART and sending completed messages to the USB output task through a queue. The messages are checked to see if they exceed the maximum size or if the last two bytes received correspond to a Carriage Return-Line Feed (CR-LF) combination. Once one of those conditions is cleared, the queue is used to pass the updated message information to the USB output task.

The second task that handles the output of the USB keyboard message waits in a blocked state until a semaphore is given based on the push buttons. Pressing a button will trigger an ISR for the button that gives the output task the semaphore. The output task then checks which button was pressed and sends the appropriate message. If the button press is for the message that can be updated, the output task first checks if it has received a new message in the queue from the UART peripheral.