I have searched information on Bit-Banding in Cortex-M3 and M4 with the GNU GCC ARM EABI NONE, I have seen basic examples on the internet but none works with GNU GCC also seems that no intention to have such feature implemented.
Can someone tell me if the LD via memory remapping really work? the best approach?
What is the best way?
ilg I checked the example of uOS, but I believe it is not the time to introduce students to the C ++, even though a more advanced topic due to the use of Arduino maintein a low level overall.
I think very valid use of C ++ in microcontrollers, but some structures and the profile of the students who have worked makes the complex topic with C ++ since it would have to enter a preliminary study of the language C ++, even if they already have guidance notions object , as that C is already almost intuitive to them.
> not the time to introduce students to the C ++
then I'm afraid you need to use a macro. see the examples in Joseph Yiu's book (The Definitive Guide to ARM Cortex-M3 and M4, chapter 6.7.4).
personally I'm no longer that impressed with bit-band accesses; yes, they are atomic and they are fast, but only work for one bit. if you have a bitfield of 2 or more bits, don't be fooled into thinking that a sequence of bit-band accesses can be used, this is equivalent to setting a sequence of different values, which might not be what you want, not to mention that some of the intermediate values might be illegal.
I'm quite positive that it can be done with plain C and a linker-script (without using the macro).
The linker-script will need two special sections; one for bitband-access and one for normal access.
Then making two instances of the variable using 'volatile __attribute__((section("NAME")))', where NAME is for instance bitband_bits or bitband_vars.
It would be safest to group those two together, however, there's no guarantee that it will work well, if more than one bitband variable is used at a time.
carlosdelfino: The macro will be just as fast as the linker-script access, it's also the safest approach if you're not using Keil.
Well, the question does not move unseen by theme.
this is very important consideration when it comes to more than one bit, actually at the end ends up not being such a definitive solution, but anyway still win the amount of instructions.
Yes doubts in Jesph Yiu book is complete on this issue, but as I saw some discussions about the use of GCC thought something might have emerged something new after 2013 about the https://answers.launchpad.net/gcc-arm-embedded/+question/228758
Thanks for the suggestions.