[avr-gcc-list] Unused registers?
Hi all, I came across a strange behaviour of avr-gcc. In one of our programs (4k in Flash) the assembler code shows that the registers r2, r3, r5 and r6 are not used at all. Since we are (as everyone, I guess) short in code space, I am wondering if there are some tricks that can make avr-gcc use those registers, too. I'm not saying avr-gcc has a bug, as those registers are used when I compile other code. Ideally, what I would like to know is if there is some special magic to make avr-gcc use all available registers and reduce the code size enough that we can squeeze in all the features asked for by marketing ;) I'm using WinAVR 20071221 but 20090313 shows the same behaviour. avr-size prog.elf textdata bss dec hex filename 4092 0 804172104c prog.elf Cheers, Thomas ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
Re: [avr-gcc-list] Unused registers?
Hi Tomas, In general it is very hard to force gcc to utilize all registers or particular registers. And if you succeed, observe that in most of the times it results in extra mov's, so it does not tend to reduce code. One exception is with framepointers. Gcc should avoid framepointers if you asked it to do so (compileroption), and make use of the extra registers. Sometimes however it does not (i do not understand why), i.e. sometimes gcc makes a framepointer for saving data instead of utilizing unused registers. In that case you can try the following trick. For example, to advise gcc to use register r6 for 'cVal': register volatile char cVal asm (r6); (Of course you can try that anyway, but i bet it will make code not shorter in general). I am curious what results you obtain. Having said that, i am sure there must be plenty of other opportunities to reduce your code. I am still shaving of bytes from my apps although i already thought they were a their minimal size a year ago. I've become a real code reduction expert by now. My motto is: You can always take off 10%. Thus, even if you already did so. ;-) Ruud http://www.femtoos.org/ On Wednesday 21 October 2009 10:59, Thomas Pircher wrote: Hi all, I came across a strange behaviour of avr-gcc. In one of our programs (4k in Flash) the assembler code shows that the registers r2, r3, r5 and r6 are not used at all. Since we are (as everyone, I guess) short in code space, I am wondering if there are some tricks that can make avr-gcc use those registers, too. I'm not saying avr-gcc has a bug, as those registers are used when I compile other code. Ideally, what I would like to know is if there is some special magic to make avr-gcc use all available registers and reduce the code size enough that we can squeeze in all the features asked for by marketing ;) I'm using WinAVR 20071221 but 20090313 shows the same behaviour. avr-size prog.elf textdata bss dec hex filename 4092 0 804172104c prog.elf Cheers, Thomas ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
RE: [avr-gcc-list] including default eeprom values in flash memory
Hi, One method, which I have read on the net also used by myself in my project is as follows. As per this we have to write the default eeprom values in our 'C' file. 1. Create one variable named eeload. 2. In your main program, if eeload !=250 (any random value) then put all your default values in EEprom. 3. And also load eeload = 250. 4. Because of this, next time eeload will be 250 default values will not be reloaded. 5. Hence after you load your main hex file, at first instant all the default eeprom values will get loaded alongwith eeload=250. 6. This part of code will never get executed in future because eeload = 250. Hope this will help you. Good Luck Prashant India -Original Message- From: avr-gcc-list-bounces+pdkharade=adorpower@nongnu.org [mailto:avr-gcc-list-bounces+pdkharade=adorpower@nongnu.org] On Behalf Of Michael Clift Sent: 21 October 2009 15:04 To: avr-gcc-list@nongnu.org Subject: [avr-gcc-list] including default eeprom values in flash memory Hi, I am using winavr, and would like to include the default eeprom values (normally output to .eep) in flash memory. I want to do this so that my application can easily default the eeprom. Whats the best way to do this? can it be done with a modification to the linker script? or should it be done in the makefile somehow? Regards, Michael. ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.423 / Virus Database: 270.14.24/2449 - Release Date: 10/20/09 18:42:00 ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
R: [avr-gcc-list] including default eeprom values in flash memory
Hi
I'm using this (for example):
File eedata.c
#include eedata.h
TOTAL_DATA total_data;
ERROR_DATA error_data;
TOTAL_DATA __attribute__((section(.eeprom))) e2total_data =
{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
ERROR_DATA __attribute__((section(.eeprom))) error_data = {0,0};
File eedata.h
#define TOTAL_DATA_ADDR 0 // Starting address of SYS_DATA image
data in eeprom
#define ERROR_DATA_ADDR (TOTAL_DATA_ADDR + sizeof(total_data))
// Starting address of ERROR_DATA image in eeprom
typedef struct {
u32 .; (fill as you need)
}TOTAL_DATA;
extern TOTAL_DATA total_data
typedef struct {
u16 ;
}ERROR_DATA;
extern ERROR_DATA error_data;
hope this help U!
Rino Tallarico
_
-Messaggio originale-
Da: avr-gcc-list-bounces+palmerinotallarico=vodafone...@nongnu.org
[mailto:avr-gcc-list-bounces+palmerinotallarico=vodafone...@nongnu.org] Per
conto di Prashant D. Kharade
Inviato: mercoledì 21 ottobre 2009 12.35
A: Michael Clift; avr-gcc-list@nongnu.org
Oggetto: RE: [avr-gcc-list] including default eeprom values in flash memory
Hi,
One method, which I have read on the net also used by myself in my
project is as follows.
As per this we have to write the default eeprom values in our 'C' file.
1. Create one variable named eeload.
2. In your main program, if eeload !=250 (any random value) then put all
your default values in EEprom.
3. And also load eeload = 250.
4. Because of this, next time eeload will be 250 default values will
not be reloaded.
5. Hence after you load your main hex file, at first instant all the
default eeprom values will get loaded alongwith eeload=250.
6. This part of code will never get executed in future because eeload =
250.
Hope this will help you.
Good Luck
Prashant
India
-Original Message-
From: avr-gcc-list-bounces+pdkharade=adorpower@nongnu.org
[mailto:avr-gcc-list-bounces+pdkharade=adorpower@nongnu.org] On
Behalf Of Michael Clift
Sent: 21 October 2009 15:04
To: avr-gcc-list@nongnu.org
Subject: [avr-gcc-list] including default eeprom values in flash memory
Hi, I am using winavr, and would like to include the default eeprom
values (normally output to .eep) in flash memory. I want to do this so
that my application can easily default the eeprom. Whats the best way to
do this? can it be done with a modification to the linker script? or
should it be done in the makefile somehow?
Regards, Michael.
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Re: [avr-gcc-list] including default eeprom values in flash memory
From: Michael Clift mich...@clift.com.au Hi, I am using winavr, and would like to include the default eeprom values (normally output to .eep) in flash memory. I want to do this so that my application can easily default the eeprom. Hello, EEPROM data in FLASH memory? then the easy way is to use the PGM space attribute to the variables you want in flash. Nayani ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
[avr-gcc-list] Re: including default eeprom values in flash memory
Michael Clift mich...@clift.com.au writes:
Hi, I am using winavr, and would like to include the default eeprom
values (normally output to .eep) in flash memory. I want to do this so
that my application can easily default the eeprom. Whats the best way
to do this? can it be done with a modification to the linker script?
or should it be done in the makefile somehow?
If you put the data into a struct like this:
struct test {
int i;
char s[6];
};
struct test x PROGMEM = {7, HELLO};
then just read byte per byte from x for sizeof(x) times and write it
into your EEPROM.
Heike
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Re: [avr-gcc-list] including default eeprom values in flash memory
On Wed, Oct 21, 2009 at 07:40:50AM -0700, Parthasaradhi Nayani wrote: From: Michael Clift mich...@clift.com.au ??? Hi, I am using winavr, and would like to include the default eeprom values (normally output to .eep) in flash memory. I want to do this so that my application can easily default the eeprom. Hello, EEPROM data in FLASH memory? then the easy way is to use the PGM space attribute to the variables you want in flash. Ditto. Declare the variables twice, once with a name that is obvious to you is EEPROM in the EEPROM space, and again with a name that is obvious to you is stored in FLASH. Then when/if you wish to restore EEPROM contents to their initial default values use the PGM modifier to read from FLASH and call the routine(s) used to write EEPROM. Duplicating the default data in your source code sounds wasteful but it will be easier to understand 6 months from now than an edit of the Makefile plus hacks to the memory segment definitions. I think it is possible that way to write the .eeprom segment to two places in memory, is just that you don't want to do it that way when there is an easier way that is also easier to understand. -- David Kelly N4HHE, dke...@hiwaay.net Whom computers would destroy, they must first drive mad. ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
Re: [avr-gcc-list] including default eeprom values in flash memory
Hi, I am using for many years a system, I published as open source (LGPL like) at http://www.ethernut.de/en/documents/phat.html. Look for 'SPIFlashFileSystem' link to a zip file. This is a complete project, but there is a subdirectory eeparams, which can be extracted from it. Common problem is, that your variables in EEPROM changes between firmware revisions. Idea is to assign a unique ID to each data structure and to place a table with these IDs, offsets and lengths at the beginning of EEPROM area. Default table occupies space in flash. However this is not suitable for uPs with limited code, I found it usefull, because the code supports also fw downgrade, while preserving variables existing in both revisions and placing default values for new ones. At 11:34 21.10.2009, Michael Clift wrote: Hi, I am using winavr, and would like to include the default eeprom values (normally output to .eep) in flash memory. I want to do this so that my application can easily default the eeprom. Whats the best way to do this? can it be done with a modification to the linker script? or should it be done in the makefile somehow? Dusan ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
Re: [avr-gcc-list] including default eeprom values in flash memory
Ditto. Declare the variables twice, once with a name that is obvious to you is EEPROM in the EEPROM space, and again with a name that is obvious to you is stored in FLASH. Then when/if you wish to restore EEPROM contents to their initial default values use the PGM modifier to read from FLASH and call the routine(s) used to write EEPROM. I have been trying to find the origin of a story, without success so far, related to restoring default EEPROM settings to factory settings. Story goes like this: A lady took her car back to the dealer, and asked that they disable the front seat passenger air bags, as her son always road there. The dealer did as the lady asked. Some time later something happened, possibly a jump start due to dead battery, which caused the ECU to restore the EEPROM to factory specs, which included turning the passenger side air bag back on. There was then an accident, where boy was killed. Even if the story is not true, it still illustrates just how hard it is to do a safe embedded system. Programming is a race between writing a program that any idiot can use, and the Universe building bigger and better idiots. The Universe is winning. -- http://www.wearablesmartsensors.com/ http://www.softwaresafety.net/ http://www.designer-iii.com/ http://www.unusualresearch.com/ ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
Re: [avr-gcc-list] including default eeprom values in flash memory
Thanks for all the responses guys, some interesting ideas. I don't really want to put all of my EEPROM data into one structure, as I have many eeprom variables with initializers distributed across a number of files. What I ended up doing, was to change the .eep output format to binary, then I copied this to an object file as described here http://www.nongnu.org/avr-libc/user-manual/FAQ.html#faq_binarydata I then linked this object into my main code. It works a treat, only I have to build my code twice to get the initial values updated to flash, once to create .eep, and again to link in the object. The main reason for doing this, is that I have a boot loader that I want our clients to be able to use, only the boot loader does not support eeprom loading. It also saves me having to program the eeprom in production. Regards, Michael. ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
