From b7bcd133470581d7bbdf491b372d14d35edeb32a Mon Sep 17 00:00:00 2001
From: Neil McKechnie <neilmck999@gmail.com>
Date: Thu, 21 Oct 2021 16:43:42 +0100
Subject: [PATCH] Fix Arduino pin pullup initial state.

If an Arduino pin was used as an input (e.g. by EXRAIL) without previously configuring it, the default pullup wouldn't be set up.  Now, on first call to the _read() method the pullup will be enabled.
---
 IODevice.cpp | 14 ++++++++++----
 IODevice.h   |  1 +
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/IODevice.cpp b/IODevice.cpp
index 5fd27ff..3456af5 100644
--- a/IODevice.cpp
+++ b/IODevice.cpp
@@ -327,12 +327,14 @@ IONotifyCallback *IONotifyCallback::first = 0;
 ArduinoPins::ArduinoPins(VPIN firstVpin, int nPins) {
   _firstVpin = firstVpin;
   _nPins = nPins;
-  uint8_t arrayLen = (_nPins+7)/8;
-  _pinPullups = (uint8_t *)calloc(2, arrayLen);
+  int arrayLen = (_nPins+7)/8;
+  _pinPullups = (uint8_t *)calloc(3, arrayLen);
   _pinModes = (&_pinPullups[0]) + arrayLen;
+  _pinInUse = (&_pinPullups[0]) + 2*arrayLen;
   for (int i=0; i<arrayLen; i++) {
     _pinPullups[i] = 0xff;  // default to pullup on, for inputs
     _pinModes[i] = 0;
+    _pinInUse[i] = 0;
   }
 }
 
@@ -357,6 +359,7 @@ bool ArduinoPins::_configure(VPIN vpin, ConfigTypeEnum configType, int paramCoun
     _pinPullups[index] &= ~mask;
     pinMode(pin, INPUT);
   }
+  _pinInUse[index] |= mask;
   return true;
 }
 
@@ -375,6 +378,7 @@ void ArduinoPins::_write(VPIN vpin, int value) {
     _pinModes[index] |= mask;
     // Since mode changes should be infrequent, use standard pinMode function
     pinMode(pin, OUTPUT);
+    _pinInUse[index] |= mask;
   }
 }
 
@@ -383,14 +387,15 @@ int ArduinoPins::_read(VPIN vpin) {
   int pin = vpin;
   uint8_t mask = 1 << ((pin-_firstVpin) % 8);
   uint8_t index = (pin-_firstVpin) / 8;
-  if (_pinModes[index] & mask) {
-    // Currently in write mode, change to read mode
+  if ((_pinModes[index] | ~_pinInUse[index]) & mask) {
+    // Currently in write mode or not initialised, change to read mode
     _pinModes[index] &= ~mask;
     // Since mode changes should be infrequent, use standard pinMode function
     if (_pinPullups[index] & mask) 
       pinMode(pin, INPUT_PULLUP);
     else
       pinMode(pin, INPUT);
+    _pinInUse[index] |= mask;
   }
   int value = !fastReadDigital(pin); // Invert (5v=0, 0v=1)
 
@@ -414,6 +419,7 @@ int ArduinoPins::_readAnalogue(VPIN vpin) {
     else
       pinMode(pin, INPUT);
   }
+
   // Since AnalogRead is also called from interrupt code, disable interrupts 
   // while we're using it.  There's only one ADC shared by all analogue inputs 
   // on the Arduino, so we don't want interruptions.
diff --git a/IODevice.h b/IODevice.h
index 5d6abc3..193b86b 100644
--- a/IODevice.h
+++ b/IODevice.h
@@ -359,6 +359,7 @@ private:
 
   uint8_t *_pinPullups;
   uint8_t *_pinModes; // each bit is 1 for output, 0 for input
+  uint8_t *_pinInUse; 
 };
 
 /////////////////////////////////////////////////////////////////////////////////////////////////////