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Example Summary

Bit-banged software UART (half-duplex) for MSPM0C1104 with auto-baud detection, echo, and ISR latency compensation.

Peripherals & Pin Assignments

Peripheral Pin Function
GPIOA PA17 SW_TX — UART TX output
GPIOA PA26 SW_RX — UART RX input (shared with TIMG14 CCP0 for baud detection)
GPIOA PA23 MARK_TIMER_ISR — measurement output for Timer ISR timing
GPIOA PA4 MARK_GPIO_ISR — measurement output for GPIO ISR timing
GPIOA PA16 Button input (falling edge) — sends test byte 0x55
GPIOA PA22 USER_LED_1 — LED indicator
TIMG6 TIMER_0 — TX/RX bit timing
TIMG14 CAPTURE_0 — baud detection capture
SYSCTL
DEBUGSS PA20 Debug Clock (SWCLK)
DEBUGSS PA19 Debug Data In Out (SWDIO)

BoosterPacks, Board Resources & Jumper Settings

Visit LP_MSPM0C1104 for LaunchPad information, including user guide and hardware files.

Pin Peripheral Function LaunchPad Pin LaunchPad Settings
PA17 GPIOA SW_TX J4_28 BoosterPack pin 28
PA26 GPIOA SW_RX / CAPTURE J4_26 BoosterPack pin 26
PA23 GPIOA MARK_TIMER_ISR J2_39 BoosterPack pin 39
PA4 GPIOA MARK_GPIO_ISR J3_19 BoosterPack pin 19
PA16 GPIOA Button J2_4 BoosterPack pin J19.4
PA22 GPIOA USER_LED_1 J2_5
  • PA22 can be connected to LED2 Blue
    • J5 ON Connect to LED2 Blue
    • J15 OFF Disconnect from LED2 Blue
PA20 DEBUGSS SWCLK N/A
  • PA20 is used by SWD during debugging
    • J101 15:16 ON Connect to XDS-110 SWCLK
    • J101 15:16 OFF Disconnect from XDS-110 SWCLK
PA19 DEBUGSS SWDIO N/A
  • PA19 is used by SWD during debugging
    • J101 13:14 ON Connect to XDS-110 SWDIO
    • J101 13:14 OFF Disconnect from XDS-110 SWDIO

Device Migration Recommendations

This project was developed for a superset device included in the LP_MSPM0C1104 LaunchPad. Please visit the CCS User’s Guide for information about migrating to other MSPM0 devices.

Low-Power Recommendations

TI recommends to terminate unused pins by setting the corresponding functions to GPIO and configure the pins to output low or input with internal pullup/pulldown resistor.

SysConfig allows developers to easily configure unused pins by selecting Board→Configure Unused Pins.

For more information about jumper configuration to achieve low-power using the MSPM0 LaunchPad, please visit the LP-MSPM0C1104 User’s Guide.

Example Usage

Compile, load and run the example. Connect a USB-UART adapter to PA17 (TX) and PA26 (RX).

The device performs auto-baud detection on the first received byte, then echoes all received data. Press the button (PA16) to send a test byte (0x55).

Clock: 24MHz SYSOSC.

Compensation calibration: see header comment in sw_uart_c1104.c. Measurement pins PA23 and PA4 can be used with a logic analyzer for ISR timing calibration.