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vTaskDelayUntil not working with mega128

Posted by Nobody/Anonymous on March 15, 2007
I implemented a simple code, with a single task . The program control is lost when it reaches vTaskDelayUntil. If simple delay (using for loop) is used the program works fine .

I have changed from mega323 to mega128 in make file
settings in FreeRtosConfig.h are
#define configUSE_PREEMPTION1
#define configUSE_IDLE_HOOK0
#define configUSE_TICK_HOOK0
#define configCPU_CLOCK_HZ( ( unsigned portLONG ) 8000000 )
#define configTICK_RATE_HZ( ( portTickType ) 1000 )
#define configMAX_PRIORITIES( ( unsigned portBASE_TYPE ) 4 )
#define configMINIMAL_STACK_SIZE( ( unsigned portSHORT ) 85 )
#define configTOTAL_HEAP_SIZE( (size_t ) ( 2500 ) )
#define configMAX_TASK_NAME_LEN( 8 )
#define configUSE_TRACE_FACILITY0
#define configUSE_16_BIT_TICKS1
#define configIDLE_SHOULD_YIELD1

RE: vTaskDelayUntil not working with mega128

Posted by Nobody/Anonymous on April 12, 2007
I also have the same problem with an ATMEGA162!!! It works fine on my ATMEGA16, I use vTaskDelay and also vTaskDelayUntil, but when I try this on ATMEGA162, it never comes again, after the call to this functions! If anyone has identified the problem, please let us know!

RE: vTaskDelayUntil not working with mega128

Posted by embeddedc on April 12, 2007
I'm not too familiar with the AVR, but having had a quick look at the two devices (16 and 162) there seems to be little difference. The 162 does have more timers through. Is it possible that the timer setup used on the 16 is not compatible with the 162 and the tick is not running? If you have a good debugger then try setting a break point in the tick interrupt. If you cannot do this then try writing a tick hook function that toggles and LED every 1000 ticks. If this does not work then maybe the timer interrupt is not running and this is the source of your problem?

RE: vTaskDelayUntil... problem solved!

Posted by Nobody/Anonymous on April 13, 2007
Hi, thanks for your respond. You´re right, I thought I had configured the timer, but there are some changes in the TIMSK register between the ATMEGA16 and the ATMEGA162 I didnt noticed! The other timer registers seem to be the same. Well, it works now for me. Here´s the code, modified for use of timer2 instead of timer1 (I need two counters for my application, and timer3 is already busy!), it´s working good.

FreeRTOS.org V4.1.3 - Copyright (C) 2003-2006 Richard Barry.

This file is part of the FreeRTOS.org distribution.

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but WITHOUT ANY WARRANTY; without even the implied warranty of
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can be applied.

See http://www.FreeRTOS.org for documentation, latest information, license
and contact details. Please ensure to read the configuration and relevant
port sections of the online documentation.


Changes from V2.6.0

+ AVR port - Replaced the inb() and outb() functions with direct memory
access. This allows the port to be built with the 20050414 build of

this port is using timer2 instead of timer1, and it is modified, for
the use with ATMEGA162. see below for further indications!

#include <stdlib.h>
#include <avr/interrupt.h>

#include "FreeRTOS.h"
#include "task.h"

* Implementation of functions defined in portable.h for the AVR port.

/* Start tasks with interrupts enables. */
#define portFLAGS_INT_ENABLED( ( portSTACK_TYPE ) 0x80 )

/* Hardware constants for timer 1. */
#define portCLEAR_COUNTER_ON_MATCH( ( unsigned portCHAR ) 0x08 )
#define portPRESCALE_64( ( unsigned portCHAR ) 0x04 )
#define portCLOCK_PRESCALER( ( unsigned portLONG ) 64 )
#define portCOMPARE_MATCH_A_INTERRUPT_ENABLE( ( unsigned portCHAR ) 0x10 )


/* We require the address of the pxCurrentTCB variable, but don't want to know
any details of its type. */
typedef void tskTCB;
extern volatile tskTCB * volatile pxCurrentTCB;


* Macro to save all the general purpose registers, the save the stack pointer
* into the TCB.
* The first thing we do is save the flags then disable interrupts. This is to
* guard our stack against having a context switch interrupt after we have already
* pushed the registers onto the stack - causing the 32 registers to be on the
* stack twice.
* r1 is set to zero as the compiler expects it to be thus, however some
* of the math routines make use of R1.
* The interrupts will have been disabled during the call to portSAVE_CONTEXT()
* so we need not worry about reading/writing to the stack pointer.

#define portSAVE_CONTEXT()\
asm volatile ("pushr0\n\t"\
"inr0, __SREG__\n\t"\
"ldsr26, pxCurrentTCB\n\t"\
"ldsr27, pxCurrentTCB + 1\n\t"\
"inr0, 0x3d\n\t"\
"stx+, r0\n\t"\
"inr0, 0x3e\n\t"\
"stx+, r0\n\t"\

* Opposite to portSAVE_CONTEXT(). Interrupts will have been disabled during
* the context save so we can write to the stack pointer.

#define portRESTORE_CONTEXT()\
asm volatile ("ldsr26, pxCurrentTCB\n\t"\
"ldsr27, pxCurrentTCB + 1\n\t"\
"ldr28, x+\n\t"\
"out__SP_L__, r28\n\t"\
"ldr29, x+\n\t"\
"out__SP_H__, r29\n\t"\
"out__SREG__, r0\n\t"\


* Perform hardware setup to enable ticks from timer 1, compare match A.
static void prvSetupTimerInterrupt( void );

* See header file for description.
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
unsigned portSHORT usAddress;

/* Place a few bytes of known values on the bottom of the stack.
This is just useful for debugging. */

*pxTopOfStack = 0x11;
*pxTopOfStack = 0x22;
*pxTopOfStack = 0x33;

/* Simulate how the stack would look after a call to vPortYield() generated by
the compiler. */

/*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */

/* The start of the task code will be popped off the stack last, so place
it on first. */
usAddress = ( unsigned portSHORT ) pxCode;
*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );

usAddress >>= 8;
*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );

/* Next simulate the stack as if after a call to portSAVE_CONTEXT().
portSAVE_CONTEXT places the flags on the stack immediately after r0
to ensure the interrupts get disabled as soon as possible, and so ensuring
the stack use is minimal should a context switch interrupt occur. */
*pxTopOfStack = ( portSTACK_TYPE ) 0x00;/* R0 */
*pxTopOfStack = portFLAGS_INT_ENABLED;

/* Now the remaining registers. The compiler expects R1 to be 0. */
*pxTopOfStack = ( portSTACK_TYPE ) 0x00;/* R1 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x02;/* R2 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x03;/* R3 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x04;/* R4 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x05;/* R5 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x06;/* R6 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x07;/* R7 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x08;/* R8 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x09;/* R9 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x10;/* R10 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x11;/* R11 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x12;/* R12 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x13;/* R13 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x14;/* R14 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x15;/* R15 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x16;/* R16 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x17;/* R17 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x18;/* R18 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x19;/* R19 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x20;/* R20 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x21;/* R21 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x22;/* R22 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x23;/* R23 */

/* Place the parameter on the stack in the expected location. */
usAddress = ( unsigned portSHORT ) pvParameters;
*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );

usAddress >>= 8;
*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );

*pxTopOfStack = ( portSTACK_TYPE ) 0x26;/* R26 X */
*pxTopOfStack = ( portSTACK_TYPE ) 0x27;/* R27 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x28;/* R28 Y */
*pxTopOfStack = ( portSTACK_TYPE ) 0x29;/* R29 */
*pxTopOfStack = ( portSTACK_TYPE ) 0x30;/* R30 Z */
*pxTopOfStack = ( portSTACK_TYPE ) 0x031;/* R31 */

/*lint +e950 +e611 +e923 */

return pxTopOfStack;

portBASE_TYPE xPortStartScheduler( void )
/* In this port we ignore the parameter and use the configUSE_PREEMPTION
definition instead. */

/* Setup the hardware to generate the tick. */

/* Restore the context of the first task that is going to run. */

/* Simulate a function call end as generated by the compiler. We will now
jump to the start of the task the context of which we have just restored. */
asm volatile ( "ret" );

/* Should not get here. */
return pdTRUE;

void vPortEndScheduler( void )
/* It is unlikely that the AVR port will get stopped. If required simply
disable the tick interrupt here. */

* Manual context switch. The first thing we do is save the registers so we
* can use a naked attribute.
void vPortYield( void ) __attribute__ ( ( naked ) );
void vPortYield( void )

asm volatile ( "ret" );

* Context switch function used by the tick. This must be identical to
* vPortYield() from the call to vTaskSwitchContext() onwards. The only
* difference from vPortYield() is the tick count is incremented as the
* call comes from the tick ISR.
void vPortYieldFromTick( void ) __attribute__ ( ( naked ) );
void vPortYieldFromTick( void )

asm volatile ( "ret" );

* Setup timer 1 compare match A to generate a tick interrupt.
static void prvSetupTimerInterrupt( void )
unsigned portLONG ulCompareMatch;
unsigned portCHAR ucLowByte;

/*This is a personal modification. The timer normally used is Timer 1, having 16 bits.
Timer1 is used for counting of external events on my app.
One of the consequences of changing the timer to one of 8 bits, is that the configTICK_RATE_HZ
cannot be too small compared to the configCPU_CLOCK_HZ. The relation between them follows the

configTICK_RATE_HZ >= configCPU_CLOCK_HZ / 16384


/* Using 8bit timer 2 to generate the tick. Correct fuses must be
selected for the configCPU_CLOCK_HZ clock. */

ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;

/* We only have 8 bits so have to scale to get our required tick rate. */
ulCompareMatch /= portCLOCK_PRESCALER; // value/64

/* Adjust for correct value. */
ulCompareMatch -= ( unsigned portLONG ) 1;

/* Setup compare match value for compare match A. Interrupts are disabled
before this is called so we need not worry here. */
ucLowByte = ( unsigned portCHAR ) ( ulCompareMatch & ( unsigned portLONG ) 0xff );
OCR2 = ucLowByte;

/* Setup clock source and compare match behaviour. */
TCCR2 = ucLowByte;//CTC, CLK/64

/* Enable the interrupt - this is okay as interrupt are currently globally
disabled. */
ucLowByte = TIMSK;
TIMSK = ucLowByte;

#if configUSE_PREEMPTION == 1

* Tick ISR for preemptive scheduler. We can use a naked attribute as
* the context is saved at the start of vPortYieldFromTick(). The tick
* count is incremented after the context is saved.
void SIG_OUTPUT_COMPARE2(void) __attribute__ ((signal, naked));
asm volatile ( "reti" );

* Tick ISR for the cooperative scheduler. All this does is increment the
* tick count. We don't need to switch context, this can only be done by
* manual calls to taskYIELD();
void SIG_OUTPUT_COMPARE2(void) __attribute__ ((signal));

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