From f543a69022de16664e8a429b6ee73d0163da0f6e Mon Sep 17 00:00:00 2001
From: DalesLandNet <peterj@daleslandnet.uk>
Date: Tue, 13 Jul 2021 11:34:45 +0100
Subject: [PATCH] [Issue #79] ESP32- Core panic when using in conjunction with
 the "preferences" library.

---
 src/SDI12.cpp        | 8 ++++----
 src/SDI12_boards.cpp | 2 +-
 src/SDI12_boards.h   | 8 ++++++++
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/SDI12.cpp b/src/SDI12.cpp
index 58e1d5c..31d1105 100644
--- a/src/SDI12.cpp
+++ b/src/SDI12.cpp
@@ -874,7 +874,7 @@ String SDI12::addCRCResponse(String &resp) {
 }
 
 char * SDI12::addCRCResponse(char *resp) {
-  char *crcStr[3] = {0};
+  char crcStr[3] = {0};
   uint16_t crc    = 0;
 
   for(int i = 0; i < strlen(resp); i++) {
@@ -979,12 +979,12 @@ takes to either a HIGH vs a LOW, and helps maintain a constant timing.
 the ISR is instructed to call handleInterrupt() when they trigger. */
 
 // 7.1 - Passes off responsibility for the interrupt to the active object.
-void SDI12::handleInterrupt(){
+void USE_INSTRUCTION_RAM SDI12::handleInterrupt(){
   if (_activeObject) _activeObject->receiveISR();
 }
 
 // 7.2 - Creates a blank slate of bits for an incoming character
-void SDI12::startChar()
+void USE_INSTRUCTION_RAM SDI12::startChar()
 {
   rxState = 0;           // got a start bit
   rxMask  = 0x01;  // 0b00000001, bit mask, lsb first
@@ -992,7 +992,7 @@ void SDI12::startChar()
 } // startChar
 
 // 7.3 - The actual interrupt service routine
-void SDI12::receiveISR()
+void USE_INSTRUCTION_RAM SDI12::receiveISR()
 {
 
   sdi12timer_t thisBitTCNT = READTIME;       // time of this data transition (plus ISR latency)
diff --git a/src/SDI12_boards.cpp b/src/SDI12_boards.cpp
index d3eacae..1298c7f 100644
--- a/src/SDI12_boards.cpp
+++ b/src/SDI12_boards.cpp
@@ -228,7 +228,7 @@ SDI12Timer::SDI12Timer(){}
 
     void SDI12Timer::configSDI12TimerPrescale(void)  {  }
     void SDI12Timer::resetSDI12TimerPrescale(void)   {  }
-    sdi12timer_t SDI12Timer::SDI12TimerRead(void)
+    sdi12timer_t USE_INSTRUCTION_RAM SDI12Timer::SDI12TimerRead(void)
     {
         // Its a one microsecond clock but we want 64uS ticks so divide by 64 i.e. right shift 6
         return((sdi12timer_t) (micros() >> 6));
diff --git a/src/SDI12_boards.h b/src/SDI12_boards.h
index 542a005..7dcd054 100644
--- a/src/SDI12_boards.h
+++ b/src/SDI12_boards.h
@@ -14,6 +14,14 @@ sensors. This library provides a general software solution, without requiring
   typedef uint8_t sdi12timer_t;
 #endif
 
+#if defined(ESP32)
+#define USE_INSTRUCTION_RAM IRAM_ATTR
+#elif defined(ESP8266)
+#define USE_INSTRUCTION_RAM  ICACHE_RAM_ATTR
+#else
+#define USE_INSTRUCTION_RAM
+#endif
+
 class SDI12Timer
 {
 public: