From ad509aed5ae4cfd696474eacdb96e1ade50593aa Mon Sep 17 00:00:00 2001
From: Patrick Fairbank <patfair@gmail.com>
Date: Tue, 14 Apr 2020 20:09:09 -0700
Subject: [PATCH] Send reset signal to PLC on match load and again on match
 start.

---
 field/arena.go |  2 ++
 plc/plc.go     | 12 ++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/field/arena.go b/field/arena.go
index 1cfbf48..8dc27c3 100644
--- a/field/arena.go
+++ b/field/arena.go
@@ -214,6 +214,7 @@ func (arena *Arena) LoadMatch(match *model.Match) error {
 	arena.FieldVolunteers = false
 	arena.FieldReset = false
 	arena.ScoringPanelRegistry.resetScoreCommitted()
+	arena.Plc.ResetMatch()
 
 	// Notify any listeners about the new match.
 	arena.MatchLoadNotifier.Notify()
@@ -404,6 +405,7 @@ func (arena *Arena) Update() {
 			enabled = true
 			sendDsPacket = true
 		}
+		arena.Plc.ResetMatch()
 	case WarmupPeriod:
 		auto = true
 		enabled = false
diff --git a/plc/plc.go b/plc/plc.go
index ec77361..00c9790 100644
--- a/plc/plc.go
+++ b/plc/plc.go
@@ -28,6 +28,7 @@ type Plc struct {
 	oldRegisters     [registerCount]uint16
 	oldCoils         [coilCount]bool
 	cycleCounter     int
+	matchResetCycles int
 }
 
 const (
@@ -231,6 +232,12 @@ func (plc *Plc) GetEthernetConnected() ([3]bool, [3]bool) {
 		}
 }
 
+// Resets the internal state of the PLC to start a new match.
+func (plc *Plc) ResetMatch() {
+	plc.coils[matchReset] = true
+	plc.matchResetCycles = 0
+}
+
 // Returns the total number of power cells scored since match start in each level of the red and blue power ports.
 func (plc *Plc) GetPowerPorts() ([3]int, [3]int) {
 	return [3]int{
@@ -408,6 +415,11 @@ func (plc *Plc) writeCoils() bool {
 		return false
 	}
 
+	if plc.matchResetCycles > 5 {
+		plc.coils[matchReset] = false // Only need a short pulse to reset the internal state of the PLC.
+	} else {
+		plc.matchResetCycles++
+	}
 	return true
 }