Update FmcLinkController port voltage algorithm

- Expose more parameters of its operation
- Final link check after setting offset voltage
- From testing it was found that headstage-64 needs a very large
amount of time to reach an acceptable votlage level to be considered off
(nearly 10 seconds)
- A new virtual SetPortVoltage method was introduced in the base link
controller to allow headstages to change the procedure depending on its
needs. In the case of headstage-64, a two-step procedure with a long
wait time after turning port voltage off, and a very large offset
voltage applied after lock.

OpenEphys.Onix/OpenEphys.Onix/ConfigureFmcLinkController.cs

@@ -28,15 +28,27 @@ public ConfigureFmcLinkController()
         [Description("Specifies the maximum link voltage at which the hub is expected to operate.")]
         public double MaxVoltage { get; set; }
 
+        [Description("Specifies the voltage step size when searching for a SERDES lock.")]
+        public double VoltageIncrement { get; set; } = 0.2;
+
         [Description("Specifies an optional link voltage offset to ensure stable operation after lock is established.")]
         public double VoltageOffset { get; set; } = 0.2;
 
-        protected virtual bool CheckLinkState(DeviceContext context)
+        protected virtual bool CheckLinkState(DeviceContext device)
         {
-            var linkState = context.ReadRegister(FmcLinkController.LINKSTATE);
+            var linkState = device.ReadRegister(FmcLinkController.LINKSTATE);
             return (linkState & FmcLinkController.LINKSTATE_SL) != 0;
         }
 
+        protected virtual void SetPortVoltage(DeviceContext device, uint voltage)
+        {
+            const int WaitUntilVoltageSettles = 200;
+            device.WriteRegister(FmcLinkController.PORTVOLTAGE, 0);
+            Thread.Sleep(WaitUntilVoltageSettles);
+            device.WriteRegister(FmcLinkController.PORTVOLTAGE, voltage);
+            Thread.Sleep(WaitUntilVoltageSettles);
+        }
+
         public override IObservable<ContextTask> Process(IObservable<ContextTask> source)
         {
             var deviceName = DeviceName;
@@ -59,21 +71,16 @@ public override IObservable<ContextTask> Process(IObservable<ContextTask> source
                 var hasLock = false;
                 var minVoltage = (uint)(MinVoltage * 10);
                 var maxVoltage = (uint)(MaxVoltage * 10);
-                var safetyVoltage = (uint)(VoltageOffset * 10);
-                for (uint voltage = minVoltage; voltage <= maxVoltage; voltage += 2)
-                {
-                    const int WaitUntilVoltageSettles = 200;
-                    device.WriteRegister(FmcLinkController.PORTVOLTAGE, 0);
-                    Thread.Sleep(WaitUntilVoltageSettles);
-                    device.WriteRegister(FmcLinkController.PORTVOLTAGE, voltage);
-                    Thread.Sleep(WaitUntilVoltageSettles);
+                var voltageOffset = (uint)(VoltageOffset * 10);
+                var voltageIncrement = (uint)(VoltageIncrement * 10);
 
+                for (uint voltage = minVoltage; voltage <= maxVoltage; voltage += voltageIncrement)
+                {
+                    SetPortVoltage(device, voltage);
                     if (CheckLinkState(device))
                     {
-                        device.WriteRegister(
-                            FmcLinkController.PORTVOLTAGE,
-                            voltage + safetyVoltage);
-                        hasLock = true;
+                        SetPortVoltage(device, voltage + voltageOffset);
+                        hasLock = CheckLinkState(device);
                         break;
                     }
                 }
@@ -93,7 +100,7 @@ public override IObservable<ContextTask> Process(IObservable<ContextTask> source
             });
         }
 
-        static class FmcLinkController
+        internal static class FmcLinkController
         {
             public const int ID = 23;
 

OpenEphys.Onix/OpenEphys.Onix/ConfigureHeadstage64.cs

@@ -1,19 +1,25 @@
 using System.Collections.Generic;
 using System.ComponentModel;
+using System.Threading;
 
 namespace OpenEphys.Onix
 {
     public class ConfigureHeadstage64 : HubDeviceFactory
     {
         PortName port;
-        readonly ConfigureFmcLinkController LinkController = new();
+        readonly ConfigureHeadstage64LinkController LinkController = new();
 
         public ConfigureHeadstage64()
         {
+            // TODO: The issue with this headstage is that its locking voltage is far, far lower than the voltage required for full
+            // functionality. Locking occurs at around 2V on the headstage (enough to turn 1.8V on). Full functionality is at 5.0 volts.
+            // Whats worse: the port voltage can only go down to 3.3V, which means that its very hard to find the true lowest voltage
+            // for a lock and then add a large offset to that.
             Port = PortName.PortA;
             LinkController.HubConfiguration = HubConfiguration.Standard;
-            LinkController.MinVoltage = 5.0;
-            LinkController.MaxVoltage = 7.0;
+            LinkController.MinVoltage = 3.3;
+            LinkController.MaxVoltage = 6.0;
+            LinkController.VoltageOffset = 3.4;
         }
 
         [Category(ConfigurationCategory)]
@@ -49,6 +55,23 @@ internal override IEnumerable<IDeviceConfiguration> GetDevices()
             yield return Bno055;
             yield return TS4231;
         }
+
+        class ConfigureHeadstage64LinkController : ConfigureFmcLinkController
+        {
+            protected override void SetPortVoltage(DeviceContext device, uint voltage)
+            {
+                // TODO: It takes a huge amount of time to get to 0, almost 10 seconds.
+                // The best we can do at the moment is drive port voltage to minimum which
+                // is an active process and then settle from there to zero volts.
+                const int WaitUntilVoltageOffSettles = 4000;
+                const int WaitUntilVoltageOnSettles = 100;
+                device.WriteRegister(FmcLinkController.PORTVOLTAGE, 33);
+                device.WriteRegister(FmcLinkController.PORTVOLTAGE, 0);
+                Thread.Sleep(WaitUntilVoltageOffSettles);
+                device.WriteRegister(FmcLinkController.PORTVOLTAGE, voltage);
+                Thread.Sleep(WaitUntilVoltageOnSettles);
+            }
+        }
     }
 
     public enum PortName