another i2c / xmmc question

Mark Mara

I need some more help. I am working on a project using xmmc. I have been using the cog_c_toggle demo code as my model. I can open an i2c bus using i2cBootOpen() in the main routine with no problems, however, if I start a cog and try to the do the i2cBootOpen() from there I get an error message.

I can demonstrate my problem using the cog_c_toggle demo code. If I put a i2cBootOpen() in toggle.c it works fine if I put the i2cBootOpen() in toggle_fw.c I get this:

bottomshotserver:my_toggle_2 mam1$ make clean
rm -f *.o *.elf *.a *.cog *.ecog *.binary
bottomshotserver:my_toggle_2 mam1$ make MODEL=xmmc BOARD=c3
propeller-elf-gcc -Os -mxmmc  -o toggle.o -c toggle.c
propeller-elf-gcc -Os  -mcog -r -o toggle_fw.cog toggle_fw.c
propeller-elf-objcopy --localize-text --rename-section .text=toggle_fw.cog toggle_fw.cog
propeller-elf-gcc -Os -mxmmc  -fno-exceptions -fno-rtti -o toggle.elf toggle.o toggle_fw.cog
toggle_fw.cog: In function `_main':
:(toggle_fw.cog+0x54): relocation truncated to fit: R_PROPELLER_SRC against symbol `_i2cBootOpen' defined in .text section in /opt/parallax/lib/gcc/propeller-elf/4.6.1/../../../../propeller-elf/lib/xmmc/libc.a(cogload.o)
collect2: ld returned 1 exit status
make: *** [toggle.elf] Error 1
bottomshotserver:my_toggle_2 mam1$

Any help would be greatly appreciated.

jazzed

It's kind of a silly way to let us know something went wrong (provided by our friends a FSF) but ....

Any time you see "relocation truncated to fit" it means your program has grown beyond the limits of the memory model.

If you need i2c access in a COG sized program you have a few choices.

1. Add some code to the COG C file usually via copy paste so you know the stack won't blow up.
2. Use a mailbox handler in a CMM/LMM/XMM* main program that can provide services.

There may be more, but these are obvious to me.

SRLM

You can also try adding the -Wl,--gc-sections -Wl,--print-gc-sections options to your gcc flags and see if that helps.

Normally when working with CMM or LMM I see something like

/opt/parallax/lib/gcc/propeller-elf/4.6.1/../../../../propeller-elf/bin/ld: main.elf section `.text' will not fit in region `hub'
/opt/parallax/lib/gcc/propeller-elf/4.6.1/../../../../propeller-elf/bin/ld: region `hub' overflowed by 20808 bytes

In your case I don't see the amount of overflow bytes.

Mark Mara

Thanks for the replies. I added the suggested flags and that caused the overflow message to be replaced with an undefined symbol error:

bottomshotserver:my_toggle_2 mam1$ make clean
rm -f *.o *.elf *.a *.cog *.ecog *.binary
bottomshotserver:my_toggle_2 mam1$ make MODEL=xmmc BOARD=c3
propeller-elf-gcc -Os -Wl,--gc-sections -Wl,--print-gc-sections -mxmmc  -o toggle.o -c toggle.c
propeller-elf-gcc -Os -Wl,--gc-sections -Wl,--print-gc-sections  -mcog -r -o toggle_fw.cog toggle_fw.c
/opt/parallax/lib/gcc/propeller-elf/4.6.1/../../../../propeller-elf/bin/ld: Removing unused section '.boot' in file '/opt/parallax/lib/gcc/propeller-elf/4.6.1/spinboot.o'
/opt/parallax/lib/gcc/propeller-elf/4.6.1/../../../../propeller-elf/bin/ld: Removing unused section '.text' in file '/opt/parallax/lib/gcc/propeller-elf/4.6.1/../../../../propeller-elf/lib/crt0_cog.o'
/opt/parallax/lib/gcc/propeller-elf/4.6.1/../../../../propeller-elf/bin/ld: Removing unused section '.text' in file '/var/folders/2d/w34p9ft573d2j2nr4l49whz00000gn/T//ccDadS1H.o'
/opt/parallax/lib/gcc/propeller-elf/4.6.1/../../../../propeller-elf/bin/ld: Removing unused section '.text' in file '/opt/parallax/lib/gcc/propeller-elf/4.6.1/../../../../propeller-elf/lib/crtend_cog.o'
/opt/parallax/lib/gcc/propeller-elf/4.6.1/../../../../propeller-elf/bin/ld: gc-sections requires either an entry or an undefined symbol
collect2: ld returned 1 exit status
make: *** [toggle_fw.cog] Error 1
bottomshotserver:my_toggle_2 mam1$

I used these flags without understanding what they do. Could you point me at any documentation? I clearly need a better understanding of what is happening.

I believe that jazzed is telling me that size of the i2c routines are such that I can not fit them into a cog so the only way to run them is from the main program. Is this correct?

SRLM

As it turns out, you've discovered the limits of where we're at with the garbage collection. I've only tested on CMM and LMM, and I forgot that it might not work (yet) with the other memory models. I'll try to take a look it but for now you'll have to take a different tack.

SRLM

You can also write your own I2C routines if you like, or maybe cut and paste from the library. I2C is a fairly light weight protocol (maybe 20 instructions each for shifting out and in a byte) so you'll have plenty of extra space in the cog if you're conservative.

jazzed

https://code.google.com/p/propgcc/source/browse/lib/sys/propeller/i2c_simple.c

https://code.google.com/p/propgcc/source/browse/lib/include/i2c.h
https://code.google.com/p/propgcc/source/browse/lib/include/i2c_driver.h

blindstar

Thanks guys. I'll try implementing my own, application specific, i2c routines.