STM32 array to control individual GPIO - c

Question

I'm new to embedded systems and C programming. I am currently trying to program a PCB using an STM32 microcontroller to control an array of 8 fans upon receipt of a single commenad. i.e 00001011 will switch on fans 5, 7 and 8. There are a total of 256 possible combinations and it wouldn't be very efficient to program each individual one.
I am thinking of using an array to achieve this using something like;
fan_array[8] = {fan1, fan2, fan3, fan4, fan5, fan6, fan7, fan8};
printf ("Input fan state"); // user would input binary number as shown above
scanf (%d, fan_array);
Would this set the GPIO pins controlling each fan high or low according to the binary values input into the array?

Answer 1

If you think about it, there are 256 possible combinations, but you're only interested in 8 fans, so all that you need to check is 8 bits:
#include <stdio.h>
#define STATE_ON 0x01
#define STATE_OFF 0x00
void enable_relay(unsigned char relay, unsigned char state)
{
/* This is a brute force approach that enables any relay/port combination:
* relay 8: PB2
* relay 7: PB4
* (...)
* relay 1: PA1
*/
switch(relay)
{
case 8:
if(state == STATE_ON)
GPIOB->ODR |= 0x0004;
else
GPIOB->ODR &= ~0x0004;
break;
case 7:
if(state == STATE_ON)
GPIOB->ODR |= 0x0010;
else
GPIOB->ODR &= ~0x0010;
break;
case 1:
if(state == STATE_ON)
GPIOA->ODR |= 0x0002;
else
GPIOA->ODR &= ~0x0002;
break;
}
}
void check_relay(unsigned char fan_map)
{
int i;
unsigned char bit;
unsigned char state;
for(i=0; i < 8; i++) {
bit = (fan_map&(0x01<<i));
state = ((bit != 0)? STATE_ON : STATE_OFF);
enable_relay( (8-i), state);
}
}
int main(void)
{
unsigned char fan_map = 0x0B; /* 0x0B = 00001011 */
check_relay(fan_map);
}
You need the 8-i part as your bit order is in reverse (fan1 as the leftmost bit) with the value order (MSB is the leftmost bit).