TM4C123G Launchpad UART Programming
Revision as of 05:33, 5 June 2019 by Jshankar (Created page with "__NOTOC__ == EK-TM4C123GXL Launchpad UART Programming == * Many of the TI ARM chips come with up to eight on-chip UART ports. They are designated as UART0 - UART7. * In the TI...")
EK-TM4C123GXL Launchpad UART Programming
- Many of the TI ARM chips come with up to eight on-chip UART ports. They are designated as UART0 - UART7.
- In the TI LaunchPad, the UART0 port of the TM4C123GH6PM is connected to the ICDI (In-Circuit Debug Interface), which is connected to a USB connector.
- This ICDI USB connection contains three distinct functions:
- Programming (downloading) using LM Flash Programming software
- Debugging using JTAG (Stellaris In-Circuit Debug Interface)
- To use as a virtual COM port
Virtual COM Port
- When the USB cable connects the Tiva LaunchPad, the device driver at the host PC establishes a virtual connection between the PC and the UART0 of the TM4C123GH6PM device.
- On the LaunchPad, the connection appears as UART0.
- On the host PC, it appears as a COM (/dev/ttyACM0) port and will work with communication software on the PC such as a terminal emulator (gtkterm, PuTTY, minicom, etc).
- It is called a virtual connection because there is no need for an additional cable to make this connection.
UART Base Addresses
TI TM4C123GH6PM can have up to 8 UART ports. They are designated as UART0 to UART7. The following shows their Base addresses in the memory map
- UART0 base: 0x4000.C000
- UART1 base: 0x4000.D000
- UART2 base: 0x4000.E000
- UART3 base: 0x4000.F000
- UART4 base: 0x4001.0000
- UART5 base: 0x4001.1000
- UART6 base: 0x4001.2000
- UART7 base: 0x4001.3000
UART Registers Setup
There are many special function registers associated with each of the above UARTs. We will be using the UART0 as an example since a virtual connection is available on the TI Tiva LaunchPad.
Baudrate Generator (UARTIBRD)
Two registers are used to set the baud rate:
- They are UART Integer Baud-Rate Divisor (UARTIBRD) and UART Fractional Baud-Rate Divisor (UARTFBRD).
- Of the 32-bit of the UARTIBRD, only lower 16 bits are used and of the 32-bit of the UARTFBRD, only the lower 6 bits are used.
- That gives us total of 22 bits (16 bits integer + 6 bits of fraction). To reduce the rate of error and use the standard baud rate, we should use both of the above divisor registers when we program the baud rate.