From 34f3abedaf5e9c25325c3d5f22043d74d9dd6d0c Mon Sep 17 00:00:00 2001
From: Harald Barth <haba@kth.se>
Date: Sat, 31 Oct 2020 22:45:06 +0100
Subject: [PATCH] different approach to Polplu board and UNUSED_PIN=127

---
 MotorDriver.h  |  6 ++++--
 MotorDrivers.h | 20 ++++++++++++++++----
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/MotorDriver.h b/MotorDriver.h
index abfb395..3f67080 100644
--- a/MotorDriver.h
+++ b/MotorDriver.h
@@ -20,6 +20,10 @@
 #define MotorDriver_h
 // Virtualised Motor shield 1-track hardware Interface
 
+#ifndef UNUSED_PIN     // sync define with the one in MotorDrivers.h
+#define UNUSED_PIN 127 // inside int8_t
+#endif
+
 class MotorDriver {
   public:
     MotorDriver(byte power_pin, byte signal_pin, byte signal_pin2, int8_t brake_pin, byte current_pin, float senseFactor, unsigned int tripMilliamps, byte faultPin);
@@ -39,7 +43,5 @@ class MotorDriver {
     float senseFactor;
     unsigned int tripMilliamps;
     int rawCurrentTripValue;
-    const byte UNUSED_PIN = 255;
-    
 };
 #endif
diff --git a/MotorDrivers.h b/MotorDrivers.h
index 809d69b..ef1e2cf 100644
--- a/MotorDrivers.h
+++ b/MotorDrivers.h
@@ -13,7 +13,9 @@
 // similar to those defined here, WITHOUT editing this file. You can put your
 // custom defines in config.h.
 
-const byte UNUSED_PIN = 255;
+#ifndef UNUSED_PIN     // sync define with the one in MotorDriver.h
+#define UNUSED_PIN 127 // inside int8_t
+#endif
 
 // MotorDriver(byte power_pin, byte signal_pin, byte signal_pin2, int8_t brake_pin, byte current_pin,
 //             float senseFactor, unsigned int tripMilliamps, byte faultPin);
@@ -28,9 +30,19 @@ const byte UNUSED_PIN = 255;
                               new MotorDriver(11, 13, UNUSED_PIN, UNUSED_PIN, A1, 2.99, 2000, UNUSED_PIN)
 
 // Pololu Motor Shield
-#define POLOLU_MOTOR_SHIELD F("POLOLU_MOTOR_SHIELD"),                               \
-                            new MotorDriver(4, 7, UNUSED_PIN, -9, A0, 18, 3000, 12), \
-                            new MotorDriver(2, 8, UNUSED_PIN, -10, A1, 18, 3000, UNUSED_PIN)
+#define POLOLU_MOTOR_SHIELD F("POLOLU_MOTOR_SHIELD"),                                                 \
+                            new MotorDriver( 9, 7, UNUSED_PIN,         -4, A0, 18, 3000,         12), \
+                            new MotorDriver(10, 8, UNUSED_PIN, UNUSED_PIN, A1, 18, 3000, UNUSED_PIN)
+//
+// Actually, on the Pololu MC33926 shield the enable lines are tied together on pin 4 and the
+// pins 9 and 10 work as "inverted brake" but as we turn on and off the tracks individually
+// via the power pins we above use 9 and 10 as power pins and 4 as "inverted brake" which in this
+// version of the code always will be high. That means this config is not usable for generating
+// a railcom cuotout in the future. For that one must wire the second ^D2 to pin 2 and define
+// the motor driver like this:
+//                          new MotorDriver(4, 7, UNUSED_PIN,  -9, A0, 18, 3000,         12)
+//                          new MotorDriver(2, 8, UNUSED_PIN, -10, A1, 18, 3000, UNUSED_PIN)
+// See Pololu dial_mc33926_shield_schematic.pdf and truth table on page 17 of the MC33926 data sheet.
 
 // Firebox Mk1
 #define FIREBOX_MK1 F("FIREBOX_MK1"),                                                  \