INTERRUPT Software Interrupt

This code example shows how to generate software interrupts and describes their operation, initialization, and interrupt handling.

Device

The device used in this code example (CE) is:

TRAVEO™ T2G CYT4BF Series

Board

The board used for testing is:

TRAVEO™ T2G evaluation kit (KIT_T2G-B-H_EVK, KIT_T2G-B-H_LITE)

Scope of work

In this example, software is used to generate an indirect interrupt, by setting the interrupt bit of a timer peripheral.

Introduction

Interrupts
TRAVEO™ T2G platform supports the following interrupt features:

Supports up to 1023 system interrupts
- Eight Cortex-M7 external interrupts and eight Cortex-M7 internal (software only) interrupts. The CPU supports up to 240 interrupts, but only sixteen interrupts are used by the TRAVEO™ T2G interrupt infrastructure. The eight external CPU interrupts support DeepSleep (WIC) functionality.
- Eight Cortex-M0+ external interrupts and eight Cortex-M0+ internal (software only) interrupts. The CPU supports up to 32 interrupts, but only sixteen interrupts are used by the TRAVEO™ T2G interrupt infrastructure. The eight external CPU interrupts support DeepSleep (WIC) functionality.
- All the available system interrupt sources are usable in Active power mode and can wake up from Sleep power mode
- A subset of available system interrupt sources capable of waking the device from DeepSleep power mode
- Four system interrupts can be mapped to each of the CPU NMI
Nested vectored interrupt controller (NVIC) integrated with each CPU core, yielding low interrupt latency
Wakeup interrupt controller (WIC) enabling interrupt detection (CPU wakeup) in DeepSleep power mode
Vector table may be placed in either flash or SRAM
Configurable priority levels (eight levels for Cortex-M7 and four levels for Cortex-M0+) for each interrupt
Level-triggered interrupt signals

More details can be found in Technical Reference Manual (TRM), Registers TRM and Data Sheet.

Hardware setup

This CE has been developed for:

TRAVEO™ T2G evaluation kit (KIT_T2G-B-H_EVK)

No changes are required from the board's default settings.
TRAVEO™ T2G Body High Lite evaluation kit (KIT_T2G-B-H_LITE)

No changes are required from the board's default settings.

Implementation

This design consists of one TCPWM counter and one user LED. Interrupts can be generated by using software to set an interrupt flag in the timer resource. For this purpose, the timer is configured to allow software setting an interrupt request from the terminal. This interrupt is processed by an interrupt handler, which will toggle the user LED.

STDIN / STDOUT setting

Initialization of the GPIO for UART is done in the cy_retarget_io_init() function.

Initialize the pin specified by CYBSP_DEBUG_UART_TX as UART TX, the pin specified by CYBSP_DEBUG_UART_RX as UART RX (these pins are connected to KitProg3 COM port)
The serial port parameters are set to 8N1 and 115200 baud

cyhal_uart_getc() returns the user input from the terminal as received data.

GPIO port pin initialization

Initialization of the GPIO port pin is done once in the cyhal_gpio_init() function.

Initialize the pin specified by CYBSP_USER_LED2 as output (initial level = H, LED turns off)

TCPWM initialization

API calls for the TCPWM initialization is done in init_Timer_Interrupt() function.

To initialize the TCPWM counter, Cy_TCPWM_Counter_Init() is called using structure cy_stc_tcpwm_counter_config_t. This is auto-coded by the Device Configurator, using the following arguments:
- Counter settings
The counter is enabled by Cy_TCPWM_Counter_Enable(), and the terminal count interrupt is enabled by setting Cy_TCPWM_SetInterruptMask() using the mask value of CY_TCPWM_INT_ON_TC
Next the interrupt handler is registered by using Cy_SysInt_Init() and enabled via the NVIC_EnableIRQ() function

Interrupt detection

if 'p' is pressed, Cy_TCPWM_SetInterrupt() is used to set the interrupt flag of the configured counter. This will cause a peripheral interrupt in the CPU which will then be handled by the registered handle_Counter_Interrupt_0() function. The handler function clears the interrupt flag by using Cy_TCPWM_ClearInterrupt() in the counter and toggles the state of the user LED2 by calling cyhal_gpio_toggle().

Run and Test

For this example, a terminal emulator is required to display outputs and receive keys pressed. You can install a terminal emulator if you do not have one. In this example, Tera Term was used as the terminal emulator.

After code compilation, perform the following steps to flash the device:

Connect the board to your PC using the provided USB cable through the KitProg3 USB connector.
Open a terminal program and select the KitProg3 COM port. Set the serial port parameters to 8N1 and 115200 baud.
Program the board using one of the following:
- Select the code example project in the Project Explorer.
- In the Quick Panel, scroll down, and click [Project Name] Program (KitProg3_MiniProg4).
After programming, the code example starts automatically. Confirm that the messages are displayed on the UART terminal.
- Terminal output on program startup
You can debug the example to step through the code. In the IDE, use the [Project Name] Debug (KitProg3_MiniProg4) configuration in the Quick Panel. For details, see the "Program and debug" section in the Eclipse IDE for ModusToolbox™ software user guide.

Note: (Only while debugging) On the CM7 CPU, some code in main() may execute before the debugger halts at the beginning of main(). This means that some code executes twice: once before the debugger stops execution, and again after the debugger resets the program counter to the beginning of main(). See KBA231071 to learn about this and for the workaround.