Quality RTOS & Embedded Software

 Real time embedded FreeRTOS RSS feed 
Quick Start Supported MCUs PDF Books Trace Tools Ecosystem


QueueSend from two tasks

Posted by Jörg Krein on February 7, 2006

when trying to write in a message queue from two tasks I get stuck in the undefined handler.
I'm using ARM STR7 with gcc. I redirected the _write() function of newlib to my putchar function. I writes in a queue from where the tx-empty isr reads.
When only one tasks uses iprintf it works.
Nonpreemption doesn't work also.
I did work in my Atmega128 port!

In main.c I wrote:

void LEDTask1( void *pvParameters )
iprintf( "Task1\r\n" );
vTaskDelay( 500/portTICK_RATE_MS );

void LEDTask2( void *pvParameters )
iprintf( "Task2\r\n" );
vTaskDelay( 1000/portTICK_RATE_MS );

In uart0.c I wrote:

void uart0_isr( void ) __attribute__((interrupt("IRQ")));
void uart0_isr( void )
char chr;
portBASE_TYPE TaskWokenByRec = pdFALSE;

if( xQueueReceiveFromISR( QueSer0Tx, &chr, &TaskWokenByRec ) == pdTRUE )
UART0_TxBUFR = chr;

//portEXIT_SWITCHING_ISR( TaskWokenByRec );

Any hints?

RE: QueueSend from two tasks

Posted by Nobody/Anonymous on February 7, 2006
Am I right in thinking from your description that the queue send is in the iprintf - and writes to QueSer0Tx.

How much stack does your iprintf function use. Traditionally printf functions can be very stack hungry. Have you checked that you are not running off the end of the task stack? Try making the stack a bit larger or checking it once you enter the undefined handler.

Which interrupt fires to end up in the undefined handler - any or are you just jumping to a random place in the code.

RE: QueueSend from two tasks

Posted by Jörg Krein on February 8, 2006
the problem lies in the too small configTOTAL_HEAP_SIZE.
If I do:
xTaskCreate( LEDTask2, "LED2", configMINIMAL_STACK_SIZE + 300, NULL, tskIDLE_PRIORITY+1, NULL );
for two tasks and heap size of 1000 it chrashes.
I had to set it to about 5000, without printf!
I wonder how 2 * 300 + 2 * 110 (minimal stack size)
needs more than 5000 bytes?
The createTask and malloc functions returned without error.


RE: QueueSend from two tasks

Posted by Nobody/Anonymous on February 8, 2006
Sounds suspicious. I think you should analyse the memory usage of your system. Do you have a decent debugger?

RE: QueueSend from two tasks

Posted by Nobody/Anonymous on February 9, 2006
yes I have a decent debugger.
It showed me that the size of the task stack is in words = 4 bytes!

pxNewTCB->pxStack = ( portSTACK_TYPE * ) pvPortMalloc( ( ( size_t )usStackDepth ) * sizeof( portSTACK_TYPE ) );

portSTACK_TYPE is defined as long in the ARM7 ports. Whereas in heap1.c :

unsigned portCHAR ucHeap[ configTOTAL_HEAP_SIZE ];

the heap is defined in bytes (portCHAR).

Ok, one has to know.
Maybe you could equal this Richard?

RE: QueueSend from two tasks

Posted by Richard on February 10, 2006
I'm can't quite follow this thread. What is the issue? The stack depth is given by the usStackDepth parameter. As per the documentation this is the number of items that can be on the stack - not the number of bytes - hence it is multiplied by sizeof( portSTACK_TYPE ).


[ Back to the top ]    [ About FreeRTOS ]    [ Privacy ]    [ Sitemap ]    [ ]

Copyright (C) Amazon Web Services, Inc. or its affiliates. All rights reserved.

Latest News

NXP tweet showing LPC5500 (ARMv8-M Cortex-M33) running FreeRTOS.

Version 10.1.1 of the FreeRTOS kernel is available for immediate download. MIT licensed.

View a recording of the "OTA Update Security and Reliability" webinar, presented by TI and AWS.


FreeRTOS and other embedded software careers at AWS.

FreeRTOS Partners

ARM Connected RTOS partner for all ARM microcontroller cores

Espressif ESP32

IAR Partner

Microchip Premier RTOS Partner

RTOS partner of NXP for all NXP ARM microcontrollers


STMicro RTOS partner supporting ARM7, ARM Cortex-M3, ARM Cortex-M4 and ARM Cortex-M0

Texas Instruments MCU Developer Network RTOS partner for ARM and MSP430 microcontrollers

OpenRTOS and SafeRTOS

Xilinx Microblaze and Zynq partner