Porting FreeRTOS 10.0.0 to LPC2148

valhalla2000 wrote on Thursday, January 04, 2018:

I am trying to get FreeRTOS running on LPC2148. I am able to call my task function.
Inside my task funtion I want to have a delay and hence called vTaskDelay(0) (to first test things out I have zero timeout). However I dont think my task is called again, i.e, brought back to RUNNING state again…
I stepped through, the functions called by vTaskDelay(0). They are


(I’ve taken portASM.s from \FreeRTOSv10.0.0\FreeRTOSv10.0.0\FreeRTOS\Source\portable\RVDS\ARM7_LPC21xx)

and this lands up in the “SWI_Handler B SWI_Handler” defined in Startup.s .

The debugger dosent proceed further . I’ve set INCLUDE_vTaskDelay = 1 in FreeRTOSConfig.h
Can anyone tell me how to proceed ?
Does the exisiting PortYield function need to be modified ?
Exisiting vPortYield functions is,

bx lr

rtel wrote on Thursday, January 04, 2018:

and this lands up in the “SWI_Handler B SWI_Handler” defined in Startup.s .

It looks like you are using the default SWI handler, which does nothing
but jump to itself, so once it is entered it never exits. You need to
have the SWI handler jump to the FreeRTOS SWI handler, which in your
case is called vPortYieldProcessor. However you don’t want to try
branching to it directly, as it may be located in memory that is too far
away for a simple ‘b’ branch - instead branch to it indirectly by
loading its address. Your vector table will then look something like
this (which I have taken from here

Vectors         LDR     PC, Reset_Addr
                 LDR     PC, Undef_Addr
                 LDR     PC, SWI_Addr ; LOAD PC WITH ADDRESS AT SWI_Addr
                 LDR     PC, PAbt_Addr
                 LDR     PC, DAbt_Addr
                 LDR     PC, [PC, #-0x0FF0]
                 LDR     PC, FIQ_Addr

Reset_Addr      DCD     Reset_Handler
Undef_Addr      DCD     Undef_Handler
SWI_Addr        DCD     vPortYieldProcessor ; FreeRTOS SWI HANDLER
PAbt_Addr       DCD     PAbt_Handler
DAbt_Addr       DCD     DAbt_Handler
IRQ_Addr        DCD     IRQ_Handler
FIQ_Addr        DCD     FIQ_Handler

valhalla2000 wrote on Friday, January 05, 2018:

Thanks Richard, its worked