From 09f09b923ced1b76c23952962e3e153c4e5af159 Mon Sep 17 00:00:00 2001
From: Felix Rusu <felix@lowpowerlab.com>
Date: Wed, 4 Apr 2018 10:36:23 -0400
Subject: [PATCH] protect AVR SPCR & SPSR

---
 SPIFlash.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/SPIFlash.cpp b/SPIFlash.cpp
index fa6ffd4..c6c2118 100644
--- a/SPIFlash.cpp
+++ b/SPIFlash.cpp
@@ -56,8 +56,10 @@ void SPIFlash::select() {
 #ifndef SPI_HAS_TRANSACTION
   noInterrupts();
 #endif
+#if defined (SPCR) && defined (SPSR)
   _SPCR = SPCR;
   _SPSR = SPSR;
+#endif
 
 #ifdef SPI_HAS_TRANSACTION
   SPI.beginTransaction(_settings);
@@ -80,15 +82,19 @@ void SPIFlash::unselect() {
 #else  
   interrupts();
 #endif
+#if defined (SPCR) && defined (SPSR)
   SPCR = _SPCR;
   SPSR = _SPSR;
+#endif
 }
 
 /// setup SPI, read device ID etc...
 boolean SPIFlash::initialize()
 {
+#if defined (SPCR) && defined (SPSR)
   _SPCR = SPCR;
   _SPSR = SPSR;
+#endif
   pinMode(_slaveSelectPin, OUTPUT);
 #ifdef SPI_HAS_TRANSACTION
   _settings = SPISettings(4000000, MSBFIRST, SPI_MODE0);