Fix a ld current ramp up bug

- During ld_i ramp up, if pwr up cmd is called, ld_i is set incorrectly

src/laser_diode/laser_diode.rs

@@ -118,12 +118,13 @@ impl LdDrive{
     }
 
     pub fn power_up(&mut self){
+        let prev_i_set = LdCurrentOutCtrlTimer::get_target_i();
         LdCurrentOutCtrlTimer::reset();        
         let _ = self.ctrl.set_i(ElectricCurrent::new::<milliampere>(0.0), Settings::LD_DRIVE_TRANSIMPEDANCE, Settings::DAC_OUT_V_MAX);
         LdPwrExcProtector::pwr_on_and_arm_protection();
         // Wait for LD Power Supply to start up before driving current to laser diode
         sleep(30);
-        self.ld_set_i(self.settings.ld_drive_current);
+        self.ld_set_i(prev_i_set);
         self.settings.pwr_on = true;
     }
 

src/laser_diode/ld_current_out_ctrl_timer.rs

@@ -63,6 +63,13 @@ impl LdCurrentOutCtrlTimer {
         }
     }
 
+    pub fn get_target_i() -> ElectricCurrent {
+        if let Some(ref mut ld_current_out_ctrl_timer ) = LdCurrentOutCtrlTimer::get() {
+            return ld_current_out_ctrl_timer.target_i
+        }
+        ElectricCurrent::new::<ampere>(0.0)
+    }
+
     pub fn set_alarm() {
         if let Some(ref mut ld_current_out_ctrl_timer ) = LdCurrentOutCtrlTimer::get() {
             ld_current_out_ctrl_timer.timeout = true;