From 292b29517b91591c3118523fcfdc56d34f5cdac5 Mon Sep 17 00:00:00 2001
From: Jon Carrier <jjcarrier@gmail.com>
Date: Wed, 6 Aug 2025 22:56:43 -0400
Subject: [PATCH] Fixed regressions for #40

Prior attempt at fixing #40 introduced the following issues:
- Output state would turn off upon loading the application. This is
  generally undesirable behavior.
- A null exception would occur if the output was on while starting up.
---
 libdp100/PowerSupply.cs | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/libdp100/PowerSupply.cs b/libdp100/PowerSupply.cs
index c56e3e9..53dfc33 100644
--- a/libdp100/PowerSupply.cs
+++ b/libdp100/PowerSupply.cs
@@ -103,6 +103,11 @@ public class PowerSupply
         /// </summary>
         private bool[] presetsValid = new bool[NumPresets];
 
+        /// <summary>
+        /// Indicates that the "Presets" object has been applied to the volatile preset's state.
+        /// </summary>
+        private bool[] presetsLoaded = new bool[NumPresets];
+
         /// <summary>
         /// Indicates that the "SystemParams" object has been populated with valid data.
         /// </summary>
@@ -525,8 +530,14 @@ public PowerSupplyResult SetOutput(bool outputOn, ushort millivolts, ushort mill
                 Output.Setpoint.Voltage = millivolts;
                 Output.Setpoint.Current = milliamps;
 
+                if (Presets[Output.Preset] == null)
+                {
+                    Presets[Output.Preset] = new PowerSupplySetpoint(Output.Preset);
+                }
+
                 // Output state affects the volatile state of a preset (group).
                 Presets[Output.Preset].Copy(Output.Setpoint);
+                presetsValid[Output.Preset] = true;
             }
 
             return result;
@@ -894,6 +905,14 @@ public PowerSupplyResult UsePreset(byte preset)
                 }
             }
 
+            if (result == PowerSupplyResult.OK)
+            {
+                if (!presetsLoaded[preset])
+                {
+                    result = SetOutput(Presets[preset]);
+                }
+            }
+
             if (result == PowerSupplyResult.OK)
             {
                 Output.Setpoint.Copy(Presets[preset]);
@@ -1042,18 +1061,6 @@ public PowerSupplyResult Reload()
                 {
                     return result;
                 }
-
-                result = UsePreset(i);
-                if (result != PowerSupplyResult.OK)
-                {
-                    return result;
-                }
-
-                result = SetOutput(Presets[i]);
-                if (result != PowerSupplyResult.OK)
-                {
-                    return result;
-                }
             }
 
             return result;