Fix always zero AnalogIn on nordic #9114
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This is quite mysterious. The underlying code hasn't changed in quite a while. nordic
AnalogIn.valuewas always returning zero on 9.x.x builds, including some early betas. The problem starts appearing when gcc13 starts being used. Compiling with gcc10 or gcc12 causes the problem to go away.While debugging, I added a printf which also caused the problem to go away. Adding tiny delay calls almost anywhere also helped. Eventually I realized it may have been due to these calls acting as an optimization memory fence. Adding
asm volatile("": : : "memory");had the same effect. I'm not sure whether this is a compiler bug or something else, but the fix works.Also removed the logic to start with
value = -1, which didn't seem necessary.