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Reducing the flash size of FreeRTOS

Posted by Lawrence Song on February 4, 2010
Hi, I'm new to embedded programming with FreeRTOS. I am using a custom board with an STM32F103 with 48 kb of ram and 128 kb of flash. I have followed the instructions provided by stefanos to make a development environment in Linux and Eclipse. He has projects for both high density and low density STM32 MCUs, with the .bin file for the low-density MCU as low as 96kb.

Here are my questions: (I searched the forums for them already. However if they have already been addressed, please point me in the right direction)

1.) The demo project I am using produces a .bin file of 127 kb. Is this the actual size of the flash that goes onto the board?

2.) If not then how do I check the size?

3.) I compared the low-density project and the high-density project... they seem almost identical. Where did the difference in flash size come from then?

Thanks!

RE: Reducing the flash size of FreeRTOS

Posted by Richard on February 4, 2010
“1.) The demo project I am using produces a .bin file of 127 kb. Is this the actual size of the flash that goes onto the board?”


If that is a .bin file then yes it is the size that is flashed into the device - but very little of that will be FreeRTOS code. Typically FreeRTOS on a Cortex M3 will take around about 7K bytes of flash space. Be careful which libraries are used as calling something like printf() can bring in huge amounts of GCC library code, which is why I normally use a very stripped down version of the string formatting functions.

“2.) If not then how do I check the size?”


Look in the map file produced by the linker. The kernel code is contained in task.c, queue.c, list.c, heap_x.c and port.c.

3) No idea. Maybe optimisation level?

Regards.

RE: Reducing the flash size of FreeRTOS

Posted by Lawrence Song on February 4, 2010
Ah yes the demo project does make use of printf! I'll get rid of them. Noob question: Where does printf print to? (there's no console FreeRTOS is there?)

So the primary source of flash fat-ness are the unnessessary libraries that are used. If I include them, but no use them, will the compiler be smart enough to leave them out?

Another possilbe cause for the bloated flash size might be related to the LCD image that the creator put in "LCD_Message.h". However when I got rid of that, only 10kb were recovered.

I'll keep working on the problem. Thanks for the tip though! IF anyone else know something about this, please do tell!

RE: Reducing the flash size of FreeRTOS

Posted by Ricky on February 5, 2010
>>> Ah yes the demo project does make use of printf! I'll get rid of them. Noob question: Where does printf print to? (there's no console FreeRTOS is there?)

Usually you have to write a function to put the data somewhere. On my project, I wrote a function called __write that outputs the string to the RS232 or USB port.

>>>So the primary source of flash fat-ness are the unnessessary libraries that are used. If I include them, but no use them, will the compiler be smart enough to leave them out?

The linker does the brainwork to figure out what can be left out. So, yes, it's smart enough.

RE: Reducing the flash size of FreeRTOS

Posted by Dave on February 5, 2010
“The linker does the brainwork to figure out what can be left out. So, yes, it's smart enough.”


That depends on the compiler being used. I think all compilers other than GCC will remove unused code by default. If you are using GCC then you have to give it some obscure compiler and linker options to get the same behavior. I'm never sure why using something like printf() brings in so much code. I think it must also bring in all the floating point code for the %f formatter?

RE: Reducing the flash size of FreeRTOS

Posted by Ricky on February 5, 2010
>>>I think it must also bring in all the floating point code for the %f formatter?
If you're using the IAR compiler, you can select which printf formatter to use, and eliminate floating point and some other stuff if you don't need them. Other compilers may give you that option as well.

RE: Reducing the flash size of FreeRTOS

Posted by Steve Macica on February 5, 2010
I wanted snprintf (does limit checks) and found a some source(snprintf.c) from Patrick Powell (papowell@astart.com). Others have added limited floating point support. http://www.ijs.si/software/snprintf/. It works well and there is not a huge memory hit.

I needed sscanf support and just added from GCC and I think it took like 30K of memory........luckily I don't need it for production code.

STM32/

RE: Reducing the flash size of FreeRTOS

Posted by Lawrence Song on February 5, 2010
Okay so after butchering the demo code I was able to get the size down to 70kb. There's got to be other things to get rid of. For example, all these include files that were part of the demo:

#include "death.h"
#include "integer.h"
#include "blocktim.h"
#include "partest.h"
#include "semtest.h"
#include "PollQ.h"
#include "flash.h"
#include "comtest2.h"


Can I get rid of any of them? It seems some of them are needed for tasks that were specific to the demo application:

/* Start the standard demo tasks. */
vCreateBlockTimeTasks();
vStartSemaphoreTasks( mainSEM_TEST_PRIORITY );
vStartPolledQueueTasks( mainQUEUE_POLL_PRIORITY );
vStartIntegerMathTasks( mainINTEGER_TASK_PRIORITY );
vStartLEDFlashTasks( mainFLASH_TASK_PRIORITY );


Are these tasks absolutely necessary for the proper function of FreeRTOS? I'm guessing that these tasks were created to demonstrate the capabilities of the operating system. Am I getting warm?

Thanks!

spotdott

RE: Reducing the flash size of FreeRTOS

Posted by Richard on February 5, 2010
No, the demo tasks are nothing to do with the kernel. See http://www.freertos.org/a00102.html , which is a bit out of date but gives you the idea. The kernel files are task.c, queue.c, list.c and port.c, and maybe a port assembly file too. Just those four files, it really is a small system. Also see http://www.freertos.org/a00017.html

Regards.

RE: Reducing the flash size of FreeRTOS

Posted by Lawrence Song on February 7, 2010
Okay so I logged all the object files during build and here is a list of binaries eating away at my precious flash space:

   text   data    bss    dec    hexfilename
800 2 31 833 341main.o
184 0 2 186 batimertest.o
1124 0 0 1124 464printf.o
624 0 0 624 270stm32f10x_it.o
360 0 2 362 16a./ParTest/ParTest.o
424 0 0 424 1a8../../Common/drivers/ST/STM32F10xFWLib/v2_0_3/src/stm32f10x_lib.o
4112 0 0 4112 1010../../Common/drivers/ST/STM32F10xFWLib/v2_0_3/src/stm32f10x_rcc.o
4724 0 0 4724 1274../../Common/drivers/ST/STM32F10xFWLib/v2_0_3/src/stm32f10x_gpio.o
4688 0 0 4688 1250../../Common/drivers/ST/STM32F10xFWLib/v2_0_3/src/stm32f10x_spi.o
680 0 0 680 2a8../../Common/drivers/ST/STM32F10xFWLib/v2_0_3/src/stm32f10x_systick.o
24724 0 0 24724 6094../../Common/drivers/ST/STM32F10xFWLib/v2_0_3/src/stm32f10x_tim.o
5688 0 0 5688 1638../../Common/drivers/ST/STM32F10xFWLib/v2_0_3/src/stm32f10x_nvic.o
3708 0 0 3708 e7c../../Common/drivers/ST/STM32F10xFWLib/v2_0_3/src/stm32f10x_flash.o
7076 0 0 7076 1ba4../../Common/drivers/ST/STM32F10xFWLib/v2_0_3/src/stm32f10x_adc.o
380 0 0 380 17c../../../Source/list.o
2244 0 0 2244 8c4../../../Source/queue.o
5052 0 256 5308 14bc../../../Source/tasks.o
520 4 0 524 20c../../../Source/portable/GCC/ARM_CM3/port.o
514 0 17432 17946 461a../../../Source/portable/MemMang/heap_2.o


Most notable is the STM32 peripheral library's tim.o (from tim.h I presume). With a whopping size of 25 kB it is one big mofo. Stefano was kind enough to send me his to compare. His tim.o is a lot smaller than mine as seen below:

272 0 12 284 11cDebug/timertest.o

24 0 0 24 18Debug/stm32f10x_it.o

290 4 8 302 12eDebug/stf_syscalls_minimal.o

173 0 52 225 e1Debug/net_launch_srv.o

288 0 20 308 134Debug/ParTest.o

6913 2 2 6917 1b05Debug/stm3210c_eval_lcd.o

1105 0 2050 3155 c53Debug/httpd.o

94868 0 0 94868 17294Debug/fs.o

306 0 256 562 232Debug/NetCalcApp.o

164 0 0 164 a4Debug/core_cm3.o

320 0 0 320 140Debug/system_stm32f10x.o

196 0 0 196 c4Debug/misc.o

908 0 0 908 38cDebug/stm32f10x_usart.o

632 0 0 632 278Debug/stm32f10x_gpio.o

1116 20 0 1136 470Debug/stm32f10x_rcc.o

840 0 0 840 348Debug/stm32f10x_spi.o

2952 0 0 2952 b88Debug/stm32f10x_tim.o

1184 0 0 1184 4a0Debug/stm32f10x_flash.o

4180 0 0 4180 1054Debug/stm32_eth.o

125 0 4 129 81Debug/flash.o

595 0 48 643 283Debug/recmutex.o

584 0 32 616 268Debug/BlockQ.o

1204 0 32 1236 4d4Debug/GenQTest.o

140 0 4 144 90Debug/integer.o

296 0 12 308 134Debug/PollQ.o

878 0 12 890 37aDebug/QPeek.o

144 0 0 144 90Debug/list.o

1248 0 0 1248 4e0Debug/queue.o

3433 4 380 3817 ee9Debug/tasks.o

312 4 0 316 13cDebug/port.o

212 0 30740 30952 78e8Debug/heap_2.o

756 0 0 756 2f4Debug/api_lib.o

1948 0 0 1948 79cDebug/api_msg.o

0 0 0 0 0Debug/err.o

276 0 0 276 114Debug/netbuf.o

0 0 0 0 0Debug/netifapi.o

851 0 16 867 363Debug/tcpip.o

512 0 0 512 200Debug/icmp.o

448 0 16 464 1d0Debug/inet.o

336 0 0 336 150Debug/inet_chksum.o

792 0 10 802 322Debug/ip.o

68 0 0 68 44Debug/ip_addr.o

1300 0 1510 2810 afaDebug/ip_frag.o

3376 4 0 3380 d34Debug/dhcp.o

0 0 0 0 0Debug/dns.o

16 0 0 16 10Debug/init.o

748 0 8228 8976 2310Debug/mem.o

212 0 9664 9876 2694Debug/memp.o

428 0 1 429 1adDebug/netif.o

1080 0 0 1080 438Debug/pbuf.o

0 0 0 0 0Debug/raw.o

0 0 0 0 0Debug/stats.o

480 0 0 480 1e0Debug/sys.o

2544 6 1 2551 9f7Debug/tcp.o

4292 0 44 4336 10f0Debug/tcp_in.o

2280 0 0 2280 8e8Debug/tcp_out.o

976 0 0 976 3d0Debug/udp.o

0 0 0 0 0Debug/asn1_dec.o

0 0 0 0 0Debug/asn1_enc.o

0 0 0 0 0Debug/mib_structs.o

0 0 0 0 0Debug/mib2.o

0 0 0 0 0Debug/msg_in.o

0 0 0 0 0Debug/msg_out.o

1808 0 201 2009 7d9Debug/etharp.o

540 0 34 574 23eDebug/sys_arch.o

1584 0 9408 10992 2af0Debug/stm32x_ethernetif.o

Why the huge difference in object file size? I'm using Timer 1 and Timer 4, btw.

Law

RE: Reducing the flash size of FreeRTOS

Posted by MEdwards on February 7, 2010
Is the STM32 systick driver really 5 times the size of tasks (tasks.o which contains the kernel implementation). That is funny.

RE: Reducing the flash size of FreeRTOS

Posted by MEdwards on February 7, 2010
Sorry, as you say its tim not systick. Next row down.

Are you using -fdata-sections, -ffunction sections in the compiler command line and --gc-sections in the linker command line?

RE: Reducing the flash size of FreeRTOS

Posted by Lawrence Song on February 8, 2010
# should use --gc-sections but the debugger does not seem to be able to cope with the option.
LINKER_FLAGS=-nostartfiles -Xlinker -o$(PROJECT_NAME).axf -Xlinker -M -Xlinker -Map=$(PROJECT_NAME).map -Xlinker --no-gc-sections


This is the linker flags in the project's makefile. Have no idea what it means. Maybe I should try --gc-sections?


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