MSP430F5529 Bare-Metal Tick Scheduler (LPM0) + PWM + ADC12 + UART Command Console

Bare-metal firmware for the MSP430F5529 LaunchPad implemented with direct register access (no RTOS, no HAL, no driver library). The project implements a tick-driven cooperative scheduler, Timer_A hardware PWM, ADC12 continuous sampling with change-threshold publishing, a UART line-based command console, and LPM0 idle between ticks.

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Demos

1) Board / wiring photo

2) ADC → PWM → LED brightness (GIF)

3) Button short press behavior (GIF)

4) Button long press behavior (GIF)

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Features

• Cooperative tick scheduler with wraparound-safe timing checks
• Periodic tick from Timer1_A CCR0 on ACLK (default period: 5 ms)
• LPM0 idle between ticks; ticker ISR exits LPM0 on ISR return
• Hardware PWM on P1.2 using Timer0_A CCR1 output mode (reset/set)
• ADC12 continuous sampling on A0 with change-threshold publishing to reduce jitter
• UART command console with double-buffered line RX and a table-driven command dispatcher
• Button debounce and short/long press events driving onboard LEDs

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Hardware & Pinout

Board: MSP430F5529 LaunchPad

• PWM output: P1.2 (TA0.1)
• ADC input: P6.0 (A0)
• UART: P4.4 (TXD), P4.5 (RXD) via USCI_A1
• LEDs: P1.0, P4.7
• Button: P1.1 (pull-up enabled)

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Build & Flash

Toolchain: Code Composer Studio (CCS) or equivalent MSP430 toolchain.

UART serial settings:

• Baud: 115200
• Format: 8N1
• Flow control: none

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Usage

Button

• Short press: toggle LED on P1.0
• Long press: toggle LED on P4.7

PWM

• PWM output on P1.2.
• Duty cycle updated from ADC: duty = adc_value / 4095.0.

UART commands

Examples:

LED P1 ON
LED P1 OFF
LED P4 ON
LED P4 OFF
SET DUTY 0.50

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Control flow

Timer1_A (ACLK) tick ISR
   -> sets tick_flag
   -> exits LPM0 on ISR return
Main loop:
   -> sleeps in LPM0
   -> wakes on tick
   -> scheduler_run(tasks, now)
   -> re-enters LPM0

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Source layout

adc.c / adc.h              # ADC12 A0 continuous sampling + threshold publishing
button.c / button.h        # debounce + short/long press state machine
cmd_led.c / cmd_led.h      # LED command handlers (P1, P4)
cmd_set.c / cmd_set.h      # SET DUTY handler
cmd_log.c / cmd_log.h      # LOG handlers (ADC stub)
command.c / command.h      # tokenize + dispatch + routing table
led.c / led.h              # onboard LED helpers (P1.0, P4.7)
main.c                     # init + main loop (sleep/wake + scheduler)
pwm.c / pwm.h              # Timer0_A PWM on P1.2 (TA0.1)
scheduler.c / scheduler.h  # cooperative scheduler + wraparound-safe timing
tasks.c / tasks.h          # task implementations (ADC->PWM, button, UART RX)
ticker.c / ticker.h        # Timer1_A CCR0 periodic tick + LPM0 wake
uart.c / uart.h            # UART + double-buffered RX line input

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References

• MSP430x5xx/6xx Family User’s Guide (Timer_A, ADC12, USCI UART, low-power modes)
• MSP430F5529 datasheet