MCUXpresso_LPC55S69/boards/lpcxpresso55s69/driver_examples/sctimer/multi_state_pwm/cm33_core0

Overview

The SCTImer multi-state project is a demonstration program of the SCTimer state machine. It shows how to set up events to be triggered in a certain state and transitioning between states. This project has two states: State 0 and State 1.

For State 0, PWM0 (24kHz 10% duty cycle) is setup, PWM0 works based on event eventFirstNumberOutput and event (eventFirstNumberOutput + 1). Meanwhile, another event is scheduled to monitor the rising edge on input 1, when rising edge detected on input 1, the SCTimer switches to State 1.

For State 1, PWM1 (24kHz 50% duty cycle) is setup, PWM1 works based on event eventSecondNumberOutput and event (eventSecondNumberOutput + 1). Meanwhile, another event is scheduled to monitor the rising edge on input 1, when rising edge detected on input 1, then SCTimer switches to State 0. To make PWM0 also work in State 1, the PWM0's events eventFirstNumberOutput and (eventFirstNumberOutput + 1) are also enabled in State 1, using API SCTIMER_ScheduleEvent. As a result, both PWM0 and PWM1 works in State 1.

The SCTimer input 1 is routed to a button GPIO, when press the button, the SCTimer switches between State 0 and State 1. In State 0, there is only PWM0 output, in State 1, there are both PWM0 and PWM1 output.

SDK version

• Version: 2.15.000

Toolchain supported

• IAR embedded Workbench 9.40.1
• Keil MDK 5.38.1
• GCC ARM Embedded 12.2
• MCUXpresso 11.8.0

Hardware requirements

• Mini/micro USB cable
• LPCXpresso55s69 board
• Personal Computer

Board settings

The switch for this examples is S1 on the board (PIO0_5)

Output signal		Board location
SCT0_OUT2    		P18-11
SCT0_OUT4    		P17-11 

Prepare the Demo

Note: MCUXpresso IDE project default debug console is semihost

1. Connect a micro USB cable between the PC host and the CMSIS DAP USB port (P6) on the board
2. Open a serial terminal with the following settings (See Appendix A in Getting started guide for description how to determine serial port number):
   • 115200 baud rate
   • 8 data bits
   • No parity
   • One stop bit
   • No flow control
3. Download the program to the target board.
4. Either press the reset button on your board or launch the debugger in your IDE to begin running the demo.

Running the demo

The log below shows example output of the SCTimer multi-state demo in the terminal window:

SCTimer example to output edge-aligned PWM signal

When user presses a switch the PWM signal will be seen from Out 2
When user presses the switch again PWM signal on Out 2 will turn off
The PWM signal from Out 4 will remain active all the time

You'll see PWM signals on P18_11 and P17_11 using an oscilloscope