I2C Keypad & LCD liabrary

Online compiler
6

Hello,

that is great.
I know nothing about your Keypad and connection with Expander, but I suppose you have the pin PB_5 connected to INT pin of the Expander. The INT pin also must have Pull-up resistor to Vcc, so internal pull-up resistor can be not enough.

You probably use the Bare Metal Mbed OS profile, but letting done all the work in ISR is not a good practice.

volatile bool flag = false;

void trigger(){
 if(!flag) flag = true;
}
 
int main(){    
    pc.printf("Start\n\r");
    data1=data2=0;
    event.mode(PullUp);
    event.fall(&trigger);
    //event.rise(&trigger);
    lcd.locate(0,0); 
    lcd.printf("KEY :%d",data1);
    while(1) 
    {
       if(flag){
        //printf("triggered!\n");
        io.write(0x0f);
        data1 = io.read();        
        io.write(0xf0);
        data2 = io.read();           
        display(data1+data2);
        //wait(0.2);
        flag = false;
       }
    }
}

BR, Jan