fn check_alarm(&self) { 
     let n = 0; 
     critical_section::with(|cs| { 
         let alarm = &self.alarms.borrow(cs); 
         let timestamp = alarm.timestamp.get(); 
         if timestamp <= self.now() { 
             self.trigger_alarm(cs) 
         } else { 
             // Not elapsed, arm it again. 
             // This can happen if it was set more than 2^32 us in the future. 
             TIMER.alarm(n).write_value(timestamp as u32); 
         } 
     }); 

     // NEW LINES HERE
     for _ in 0..1000 {
         cortex_m::asm::nop()
     }
     // END NEW LINES
  
     // clear the irq 
     TIMER.intr().write(|w| w.set_alarm(n, true)); 
 }