Inability to read 0 value from INPUT.

[AMat.1]

I was trying to program STM32 to read the values and toggle the LED, but it didn't work. Please help

[Uwe Bonnes]

(0 << 1) evaluates to 0 and if (0) never executes!

[AMat.1]

Sorry I didnt fully understood, can you explain more ?

[Uwe Bonnes]

if (GPIOA->IDR & (0 << 1)) will never get true!

[AMat.1]

if IDR is all 0's and its ANDed with 0 , how will it never be true? for example , IDR = 0 and 1st bit = 0 (0&0) = True = 1

[Uwe Bonnes · Accepted solution]

You use bitwise and with a bitmask of 0, so the result = 0. (0&0) = 0 = false.

[AMat.1]

lol , thanks, that makes sense

the 0&0=1 was an oopsie

[Tesla DeLorean]

You also probably don't want to blind write into the entire ODR, as it will impact all bits. Use BSRR for such writes

GPIOC->ODR |= (1 << 13); // set PC13

GPIOC->ODR &= ~(1 << 13); // reset PC13 (uses tilde, stupid forum prints as minus)

[Uwe Bonnes]

Better use BSRR: Only one access:

GPIOC->BSRR = (1 << 13); // set PC13

GPIOC->BSRR = (1 << (13 + 16)); // reset PC13