you should look where the size of the heap is defined and try to increase it
in below definitions i specified heap size as 1024.suppose if i increased r decreased also its showing the same error...
#define configUSE_PREEMPTION 1
#define configUSE_IDLE_HOOK 0
#define configUSE_TICK_HOOK 0
#define configTICK_RATE_HZ ( ( portTickType ) 1000 )
#define configCPU_CLOCK_HZ ( ( unsigned long ) 20000000 )
#define configMAX_PRIORITIES ( ( unsigned portBASE_TYPE ) 4 )
#define configMINIMAL_STACK_SIZE ( 105 )
#define configTOTAL_HEAP_SIZE ( ( size_t ) 1024 )
#define configMAX_TASK_NAME_LEN ( 4 )
#define configUSE_TRACE_FACILITY 0
#define configUSE_16_BIT_TICKS 1
#define configIDLE_SHOULD_YIELD 1