EECS 388 Embedded Systems Example Program Structure. Gary J. Minden August 24, 2016

Transcription

1 EECS 388 Embedded Systems Example Program Structure Gary J. Minden August 24,

2 EECS 388 Program Structure Initial program structure A set of Main, Tasks, and Timer Tasks consists of: Task variables (State variables) Task initialization Task execution Generally, no arguments to the Task Main consists of: CPU initialization Timer initialization Calling each Task in an infinite loop 2

3 EECS 388 Program Structure Timer consists of: Timer state variables ********************************************************************* The number of clock cycles between SysTick interrupts. The SysTick interrupt period is 0.1 ms (10 KHz) All events in the application occur at some fraction of this clock rate. The number of SysTick clock ticks that have occurred. ********************************************************************* extern uint32_t SysTickFrequency_Nbr = 10000; extern uint32_t SysTickCount_Nbr = 0; Interrupt Service Routine (ISR) SysTick Interrupt Increment TickCount Return 3

4 Task to Blink LED Is task initialized? If not, initialize Invoke Blink_Execute Return Task_LEDBlink.c Initialized No Yes Blink_Init Blink_Execute Return 4

5 Task to Blink LED -- Initialization Allocate state variables static uint32_t Task_LEDBlink_NextExecute = 0; static uint32_t Task_LEDBlink_DeltaExecute; static bool Enable GPIOG Initialize GPIOG peripheral Compute NextExecuteTime Next execution time Number of SysTicks between execution Task_LEDBlink_Initialized = false; State of task initialization Blink_Init Enable GPIOG Configure GPIOG Set NextExecute Time Return 5

6 Task to Blink LED -- Execute Is it time to change LED? If so, change LED Compute NextExecuteTime Return Yes Blink_Execute Time to Execute Yes LED On? No No Turn LED Off Turn LED On Set NextExecute Time Return 6

7 Mainline Initialize SystemClock Initialize SysTickClock Enable SysTickClock interrupts Loop invoking Task_LEDBlink.c Main.c Initialize SystemClock Initialize SysTickClock Enable SysTickClock Interrupts While(1) T Execute Task_LEDBlink.c 7

8 Example Program -- Program_LEDBlinky.c ***************************************************************************** Program_LEDBlinky.c Blink the LED and display number of SysTicks Author: Gary J. Minden Organization: KU/EECS/EECS 388 Date: Version: 1.0 Purpose: Example program that demonstrates: (1) setting up the SysTick Timer and interrupt (2) setting up a GPIO pin (LED) (3) setting up the OLED display (4) drawing on the OLED (5) blinking (toggling) a LED (6) formatting and displaying a number on the OLED Notes: Updated at KU and adapted from the TI LM3S1968 blinky and other examples. Date: (B60816) Moved task code to separate files. Changed structure of task code. See individual tasks. Updated basic types. ***************************************************************************** 8

9 Include Files #include "inc/hw_ints.h" #include "inc/hw_memmap.h" #include "inc/hw_sysctl.h" #include "inc/hw_types.h" #include <stddef.h> #include <stdbool.h> #include <stdint.h> #include <stdarg.h> #include "driverlib/sysctl.h" #include "driverlib/systick.h" #include "driverlib/gpio.h" #include "Drivers/rit128x96x4.h" #include "stdio.h" 9

10 Global Variables ***************************************************************************** The speed of the processor clock in Hertz, which is therefore the speed of the clock that is fed to the peripherals. ***************************************************************************** uint32_t g_ulsystemclock; ***************************************************************************** The number of clock cycles between SysTick interrupts. The SysTick interrupt period is 0.1 ms. All events in the application occur at some fraction of this clock rate. The number of SysTick clock ticks that have occurred. ***************************************************************************** extern uint32_t SysTickFrequency_Nbr = 10000; extern uint32_t SysTickCount_Nbr = 0; 10

11 External Tasks ***************************************************************************** External tasks ***************************************************************************** extern void Task_LEDBlink(); extern void Task_ReportSysTick(); extern void Task_Display_ADC(); 11

12 SysTick Interrupt Service Routine ***************************************************************************** SysTick interrupt service routine (ISR). ***************************************************************************** extern void SysTickIntHandler(void) { } Increment the tick count. SysTickCount_Nbr++; 12

13 Blinky_Initialization static uint32_t Task_LEDBlink_NextExecute = 0; Next execution time static uint32_t Task_LEDBlink_DeltaExecute; Number of SysTicks between execution static bool Task_LEDBlink_Initialized = false; State of task initialization extern void Task_LEDBlink() { uint32_t LED_Data = 0; State Variables Task Name if (!Task_LEDBlink_Initialized ) { Enable the GPIO Port G. SysCtlPeripheralEnable( SYSCTL_PERIPH_GPIOG ); Enable Configure GPIO_G to drive the Status LED. GPIOPinTypeGPIOOutput( GPIO_PORTG_BASE, GPIO_PIN_2 ); GPIOPadConfigSet( GPIO_PORTG_BASE, GPIO_PIN_2, GPIO_STRENGTH_2MA, GPIO_PIN_TYPE_STD_WPU ); The delta between executions is 50 ms. The initial time to execute is Delta from now. Task_LEDBlink_DeltaExecute = (( 50 * SysTickFrequency_Nbr ) / 1000 ); Task_LEDBlink_NextExecute = SysTickCount_Nbr + Task_LEDBlink_DeltaExecute; Task is initialized. Task_LEDBlink_Initialized = true; Configure Next Execution Time } 13

14 Blinky_Execute ***************************************************************************** Task execution. ***************************************************************************** if ( SysTickCount_Nbr >= Task_LEDBlink_NextExecute ) { Toggle the LED. LED_Data = GPIOPinRead( GPIO_PORTG_BASE, GPIO_PIN_2 ); LED_Data = LED_Data ^ 0x04; GPIOPinWrite( GPIO_PORTG_BASE, GPIO_PIN_2, LED_Data ); Advance Task_LEDBlink_NextExecute time. Time to Execute? Read LED Value Toggle Write LED Value Task_LEDBlink_NextExecute = SysTickCount_Nbr + Task_LEDBlink_DeltaExecute; } } Next Execution Time 14

15 Main Program Initialization ***************************************************************************** Main program to initialize hardware and execute Tasks. ***************************************************************************** int main( void ) { volatile unsigned long ulloop; Set the clocking to run directly from the crystal. SysCtlClockSet( SYSCTL_SYSDIV_4 SYSCTL_USE_PLL SYSCTL_OSC_MAIN SYSCTL_XTAL_8MHZ ); Get the system clock speed. g_ulsystemclock = SysCtlClockGet(); Configure SysTick to periodically interrupt. SysTickPeriodSet( g_ulsystemclock / SysTickFrequency_Nbr ); SysTickIntEnable(); SysTickEnable(); Configure SysClk Get SysClk Rate Configure SysTick 15

16 Main Program Execution } Execute Tasks while ( 1 ) { Task_LEDBlink(); Task_ReportSysTick(); Task_Display_ADC(); } 16