I'm coming from this problem where I had the issue that one GPIO write would influence the level of another pin. (GPIO19 would influence GPIO13).
When changing the set/clear operation from
= the behaviour is suddenly correct:
// clear GPIO19 *(GPCLEAR0) |= (1u << 19); // does not work *(GPCLEAR0) = (1u << 19); // works
I'm aware that there are registers that should only be written to (like clearing interrupt flag).
However, the datasheet of BCM2835 does not mention to not read
In fact, the datasheet claims that this register is read+write.
So why is it working with
= and not with the more "logical"