Merge branch 'esp8266' of https://github.com/esp8266/Arduino into esp8266

cores/esp8266/Arduino.h

@@ -212,6 +212,7 @@ void loop(void);
 
 #include "HardwareSerial.h"
 #include "Esp.h"
+#include "debug.h"
 
 uint16_t makeWord(uint16_t w);
 uint16_t makeWord(byte h, byte l);
@@ -229,6 +230,7 @@ long random(long, long);
 void randomSeed(unsigned int);
 long map(long, long, long, long, long);
 
+
 #endif
 
 #include "pins_arduino.h"

cores/esp8266/Print.cpp

@@ -18,6 +18,7 @@
  
  Modified 23 November 2006 by David A. Mellis
  Modified December 2014 by Ivan Grokhotkov
+ Modified May 2015 by Michael C. Miller - esp8266 progmem support
  */
 
 #include <stdlib.h>
@@ -42,6 +43,18 @@ size_t ICACHE_FLASH_ATTR Print::write(const uint8_t *buffer, size_t size) {
     return n;
 }
 
+size_t ICACHE_FLASH_ATTR Print::print(const __FlashStringHelper *ifsh) {
+    PGM_P p = reinterpret_cast<PGM_P>(ifsh);
+
+    size_t n = 0;
+    while (1) {
+        uint8_t c = pgm_read_byte(p++);
+        if (c == 0) break;
+        n += write(c);
+    }
+    return n;
+}
+
 size_t ICACHE_FLASH_ATTR Print::print(const String &s) {
     return write(s.c_str(), s.length());
 }
@@ -92,6 +105,12 @@ size_t ICACHE_FLASH_ATTR Print::print(double n, int digits) {
     return printFloat(n, digits);
 }
 
+size_t ICACHE_FLASH_ATTR Print::println(const __FlashStringHelper *ifsh) {
+    size_t n = print(ifsh);
+    n += println();
+    return n;
+}
+
 size_t ICACHE_FLASH_ATTR Print::print(const Printable& x) {
     return x.printTo(*this);
 }

cores/esp8266/Print.h

@@ -63,6 +63,7 @@ class Print {
             return write((const uint8_t *) buffer, size);
         }
 
+        size_t print(const __FlashStringHelper *);
         size_t print(const String &);
         size_t print(const char[]);
         size_t print(char);
@@ -74,6 +75,7 @@ class Print {
         size_t print(double, int = 2);
         size_t print(const Printable&);
 
+        size_t println(const __FlashStringHelper *);
         size_t println(const String &s);
         size_t println(const char[]);
         size_t println(char);

cores/esp8266/WString.cpp

@@ -4,6 +4,7 @@
  Copyright (c) 2009-10 Hernando Barragan.  All rights reserved.
  Copyright 2011, Paul Stoffregen, paul@pjrc.com
  Modified by Ivan Grokhotkov, 2014 - esp8266 support
+ Modified by Michael C. Miller, 2015 - esp8266 progmem support
 
  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
@@ -44,6 +45,11 @@ ICACHE_FLASH_ATTR String::String(const String &value) {
     *this = value;
 }
 
+ICACHE_FLASH_ATTR String::String(const __FlashStringHelper *pstr) {
+    init();
+    *this = pstr; // see operator =
+}
+
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
 ICACHE_FLASH_ATTR String::String(String &&rval) {
     init();
@@ -167,6 +173,16 @@ String & ICACHE_FLASH_ATTR String::copy(const char *cstr, unsigned int length) {
     return *this;
 }
 
+String & ICACHE_FLASH_ATTR String::copy(const __FlashStringHelper *pstr, unsigned int length) {
+    if (!reserve(length)) {
+        invalidate();
+        return *this;
+    }
+    len = length;
+    strcpy_P(buffer, (PGM_P)pstr);
+    return *this;
+}
+
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
 void ICACHE_FLASH_ATTR String::move(String &rhs) {
     if(buffer) {
@@ -223,6 +239,14 @@ String & ICACHE_FLASH_ATTR String::operator =(const char *cstr) {
     return *this;
 }
 
+String & ICACHE_FLASH_ATTR String::operator = (const __FlashStringHelper *pstr)
+{
+    if (pstr) copy(pstr, strlen_P((PGM_P)pstr));
+    else invalidate();
+
+    return *this;
+}
+
 // /*********************************************/
 // /*  concat                                   */
 // /*********************************************/
@@ -299,6 +323,17 @@ unsigned char ICACHE_FLASH_ATTR String::concat(double num) {
     return concat(string, strlen(string));
 }
 
+unsigned char ICACHE_FLASH_ATTR String::concat(const __FlashStringHelper * str) {
+    if (!str) return 0;
+    int length = strlen_P((PGM_P)str);
+    if (length == 0) return 1;
+    unsigned int newlen = len + length;
+    if (!reserve(newlen)) return 0;
+    strcpy_P(buffer + len, (PGM_P)str);
+    len = newlen;
+    return 1;
+}
+
 /*********************************************/
 /*  Concatenate                              */
 /*********************************************/
@@ -373,6 +408,13 @@ StringSumHelper & ICACHE_FLASH_ATTR operator +(const StringSumHelper &lhs, doubl
     return a;
 }
 
+StringSumHelper & ICACHE_FLASH_ATTR operator + (const StringSumHelper &lhs, const __FlashStringHelper *rhs)
+{
+    StringSumHelper &a = const_cast<StringSumHelper&>(lhs);
+    if (!a.concat(rhs))	a.invalidate();
+    return a;
+}
+
 // /*********************************************/
 // /*  Comparison                               */
 // /*********************************************/

cores/esp8266/WString.h

@@ -26,15 +26,17 @@
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
-#define PROGMEM
+#include <pgmspace.h>
 
 // An inherited class for holding the result of a concatenation.  These
 // result objects are assumed to be writable by subsequent concatenations.
 class StringSumHelper;
 
-typedef char* __FlashStringHelper;
+// an abstract class used as a means to proide a unique pointer type
-//#define F(str)  []() -> const char * { static const char tmp[] ICACHE_RODATA_ATTR = str; return &tmp[0]; }()
+// but really has no body
-#define F(str) str
+class __FlashStringHelper;
+#define F(string_literal) (reinterpret_cast<const __FlashStringHelper *>(PSTR(string_literal)))
+
 
 // The string class
 class String {
@@ -53,6 +55,7 @@ class String {
         // be false).
         String(const char *cstr = "");
         String(const String &str);
+        String(const __FlashStringHelper *str);
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
         String(String &&rval);
         String(StringSumHelper &&rval);
@@ -81,6 +84,7 @@ class String {
         // marked as invalid ("if (s)" will be false).
         String & operator =(const String &rhs);
         String & operator =(const char *cstr);
+        String & operator = (const __FlashStringHelper *str);
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
         String & operator =(String &&rval);
         String & operator =(StringSumHelper &&rval);
@@ -101,6 +105,7 @@ class String {
         unsigned char concat(unsigned long num);
         unsigned char concat(float num);
         unsigned char concat(double num);
+        unsigned char concat(const __FlashStringHelper * str);
 
         // if there's not enough memory for the concatenated value, the string
         // will be left unchanged (but this isn't signalled in any way)
@@ -144,6 +149,10 @@ class String {
             concat(num);
             return (*this);
         }
+        String & operator += (const __FlashStringHelper *str){
+            concat(str);
+            return (*this);
+        }
 
         friend StringSumHelper & operator +(const StringSumHelper &lhs, const String &rhs);
         friend StringSumHelper & operator +(const StringSumHelper &lhs, const char *cstr);
@@ -155,6 +164,7 @@ class String {
         friend StringSumHelper & operator +(const StringSumHelper &lhs, unsigned long num);
         friend StringSumHelper & operator +(const StringSumHelper &lhs, float num);
         friend StringSumHelper & operator +(const StringSumHelper &lhs, double num);
+        friend StringSumHelper & operator +(const StringSumHelper &lhs, const __FlashStringHelper *rhs);
 
         // comparison (only works w/ Strings and "strings")
         operator StringIfHelperType() const {
@@ -237,6 +247,7 @@ class String {
 
         // copy and move
         String & copy(const char *cstr, unsigned int length);
+        String & copy(const __FlashStringHelper *pstr, unsigned int length);
 #ifdef __GXX_EXPERIMENTAL_CXX0X__
         void move(String &rhs);
 #endif

cores/esp8266/debug.cpp

@@ -0,0 +1,35 @@
+/* 
+ debug.cpp - debug helper functions
+ Copyright (c) 2015 Markus Sattler. All rights reserved.
+ This file is part of the esp8266 core for Arduino environment.
+ 
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ This library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with this library; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include "Arduino.h"
+#include "debug.h"
+
+void ICACHE_RAM_ATTR hexdump(uint8_t *mem, uint32_t len, uint8_t cols) {
+    os_printf("\n[HEXDUMP] Address: 0x%08X len: 0x%X (%d)", mem, len, len);
+    for(uint32_t i = 0; i < len; i++) {
+        if(i % cols == 0) {
+            os_printf("\n[0x%08X] 0x%08X: ", mem, i);
+        }
+        os_printf("%02X ", *mem);
+        mem++;
+    }
+    os_printf("\n");
+}
+

cores/esp8266/debug.h

@@ -5,4 +5,7 @@
 // #define DEBUGV(...) ets_printf(__VA_ARGS__)
 #define DEBUGV(...)
 
+void hexdump(uint8_t *mem, uint32_t len, uint8_t cols = 16);
+
+
 #endif//ARD_DEBUG_H

cores/esp8266/libc_replacements.c

@@ -116,7 +116,7 @@ char* strncpy(char * dest, const char * src, size_t n) {
     return ets_strncpy(dest, src, n);
 }
 
-size_t strnlen(const char *s, size_t len) {
+size_t ICACHE_FLASH_ATTR strnlen(const char *s, size_t len) {
     // there is no ets_strnlen
     const char *cp;
     for (cp = s; len != 0 && *cp != '\0'; cp++, len--);
@@ -127,7 +127,7 @@ char* strstr(const char *haystack, const char *needle) {
     return ets_strstr(haystack, needle);
 }
 
-char* strchr(const char * str, int character) {
+char* ICACHE_FLASH_ATTR strchr(const char * str, int character) {
     while(1) {
         if(*str == 0x00) {
             return NULL;
@@ -139,7 +139,7 @@ char* strchr(const char * str, int character) {
     }
 }
 
-char * strrchr(const char * str, int character) {
+char * ICACHE_FLASH_ATTR strrchr(const char * str, int character) {
     char * ret = NULL;
     while(1) {
         if(*str == 0x00) {
@@ -223,7 +223,7 @@ char* ICACHE_FLASH_ATTR strtok(char * str, const char * delimiters) {
     return ret;
 }
 
-int strcasecmp(const char * str1, const char * str2) {
+int ICACHE_FLASH_ATTR strcasecmp(const char * str1, const char * str2) {
     int d = 0;
     while(1) {
         int c1 = tolower(*str1++);

cores/esp8266/pgmspace.cpp

@@ -0,0 +1,161 @@
+/*
+pgmspace.cpp - string functions that support PROGMEM
+Copyright (c) 2015 Michael C. Miller.  All right reserved.
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 2.1 of the License, or (at your option) any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#include <ctype.h>
+#include "pgmspace.h"
+
+size_t ICACHE_FLASH_ATTR strnlen_P(const char* s, size_t size) {
+    const char* cp;
+    for (cp = s; size != 0 && pgm_read_byte(cp) != '\0'; cp++, size--);
+    return (size_t)(cp - s);
+}
+
+void* ICACHE_FLASH_ATTR memcpy_P(void* dest, const void* src, size_t count) {
+    const uint8_t* read = reinterpret_cast<const uint8_t*>(src);
+    uint8_t* write = reinterpret_cast<uint8_t*>(dest);
+
+    while (count)
+    {
+        *write++ = pgm_read_byte(read++);
+        count--;
+    }
+
+    return dest;
+}
+
+char* ICACHE_FLASH_ATTR strncpy_P(char* dest, const char* src, size_t size) {
+    const char* read = src;
+    char* write = dest;
+    char ch = '.';
+    while (size > 0 && ch != '\0')
+    {
+        ch = pgm_read_byte(read++);
+        *write++ = ch;
+        size--;
+    } 
+
+    return dest;
+}
+
+char* ICACHE_FLASH_ATTR strncat_P(char* dest, const char* src, size_t size) {
+    char* write = dest;
+
+    while (*write != '\0')
+    {
+        write++;
+    }
+    
+    const char* read = src;
+    char ch = '.';
+
+    while (size > 0 && ch != '\0')
+    {
+        ch = pgm_read_byte(read++);
+        *write++ = ch;
+
+        size--;
+    }
+
+    if (ch != '\0')
+    {
+        *write = '\0';
+    }
+
+    return dest;
+}
+
+int ICACHE_FLASH_ATTR strncmp_P(const char* str1, const char* str2P, size_t size) {
+    int result = 0;
+
+    while (size > 0)
+    {
+        char ch1 = *str1++;
+        char ch2 = pgm_read_byte(str2P++);
+        result = ch1 - ch2;
+        if (result != 0 || ch2 == '\0')
+        {
+            break;
+        }
+
+        size--;
+    }
+
+    return result;
+}
+
+int ICACHE_FLASH_ATTR strncasecmp_P(const char* str1, const char* str2P, size_t size) {
+    int result = 0;
+
+    while (size > 0)
+    {
+        char ch1 = tolower(*str1++);
+        char ch2 = tolower(pgm_read_byte(str2P++));
+        result = ch1 - ch2;
+        if (result != 0 || ch2 == '\0')
+        {
+            break;
+        }
+
+        size--;
+    }
+
+    return result;
+}
+
+int	ICACHE_FLASH_ATTR printf_P(const char* formatP, ...) {
+    int ret;
+    va_list arglist;
+    va_start(arglist, formatP);
+
+    size_t fmtLen = strlen_P(formatP);
+    char* format = new char[fmtLen + 1];
+    strcpy_P(format, formatP);
+
+    ret = os_printf(format, arglist);
+
+    delete [] format;
+
+    va_end(arglist);
+    return ret;
+}
+
+int	ICACHE_FLASH_ATTR snprintf_P(char* str, size_t strSize, const char* formatP, ...) {
+    int ret;
+    va_list arglist;
+    va_start(arglist, formatP);
+
+    ret = vsnprintf_P(str, strSize, formatP, arglist);
+
+    va_end(arglist);
+    return ret;
+}
+
+int	ICACHE_FLASH_ATTR vsnprintf_P(char* str, size_t strSize, const char* formatP, va_list ap) {
+    int ret;
+
+    size_t fmtLen = strlen_P(formatP);
+    char* format = new char[fmtLen + 1];
+    strcpy_P(format, formatP);
+
+    ret = ets_vsnprintf(str, strSize, format, ap);
+
+    delete [] format;
+
+    return ret;
+}

cores/esp8266/pgmspace.h

@@ -12,13 +12,11 @@ extern "C" {
 }
 #endif
 
-#define PROGMEM
+#define PROGMEM     ICACHE_RODATA_ATTR
 #define PGM_P  		const char *
-#define PSTR(str) 	(str)
+#define PGM_VOID_P  const void *
+#define PSTR(s) (__extension__({static const char __c[] PROGMEM = (s); &__c[0];}))
 
-#define vsnprintf_P(...) 	ets_vsnprintf( __VA_ARGS__ )
-#define snprintf_P(...) 	snprintf( __VA_ARGS__ )
-#define printf_P(...)       os_printf(__VA_ARGS__)
 
 #define _SFR_BYTE(n) (n)
 
@@ -32,23 +30,56 @@ typedef uint16_t prog_uint16_t;
 typedef int32_t prog_int32_t;
 typedef uint32_t prog_uint32_t;
 
-#define memcpy_P(dest, src, num) 	memcpy((dest), (src), (num))
+#define SIZE_IRRELEVANT 0x7fffffff
-#define strcpy_P(dest, src) 		strcpy((dest), (src))
-#define strcat_P(dest, src) 		strcat((dest), (src))
-#define strcmp_P(a, b) 				strcmp((a), (b))
-#define strstr_P(a, b) 				strstr((a), (b))
-#define strlen_P(s) 				strlen((const char *)(s))
-#define strcasecmp_P(a, b)          strcasecmp((a), (b))
-#define strncpy_P(dest, src, size) 		strncpy((dest), (src), (size))
-#define strncat_P(dest, src, size) 		strncat((dest), (src), (size))
-#define strncmp_P(a, b, size) 			strncmp((a), (b), (size))
-#define strnlen_P(s, size) 				strnlen((const char *)(s), (size))
-#define strncasecmp_P(a, b, size)       strncasecmp((a), (b), (size))
 
-#define pgm_read_byte(addr) 		(*(const unsigned char *)(addr))
+extern void* memcpy_P(void* dest, const void* src, size_t count);
-#define pgm_read_word(addr) 		(*(const unsigned short *)(addr))
+
-#define pgm_read_dword(addr) 		(*(const unsigned long *)(addr))
+extern char* strncpy_P(char* dest, const char* src, size_t size);
-#define pgm_read_float(addr) 		(*(const float *)(addr))
+#define strcpy_P(dest, src)          strncpy_P((dest), (src), SIZE_IRRELEVANT)
+
+extern char* strncat_P(char* dest, const char* src, size_t size);
+#define strcat_P(dest, src)          strncat_P((dest), (src), SIZE_IRRELEVANT)
+
+extern int strncmp_P(const char* str1, const char* str2P, size_t size);
+#define strcmp_P(str1, str2P)          strncmp_P((str1), (str2P), SIZE_IRRELEVANT)
+
+extern int strncasecmp_P(const char* str1, const char* str2P, size_t size);
+#define strcasecmp_P(str1, str2P)          strncasecmp_P((str1), (str2P), SIZE_IRRELEVANT)
+
+extern size_t strnlen_P(const char *s, size_t size);
+#define strlen_P(strP)          strnlen_P((strP), SIZE_IRRELEVANT)
+
+extern int	printf_P(const char *formatP, ...);
+extern int	snprintf_P(char *str, size_t strSize, const char *formatP, ...);
+extern int	vsnprintf_P(char *str, size_t strSize, const char *formatP, va_list ap);
+
+// flash memory must be read using 32 bit aligned addresses else a processor
+// exception will be triggered
+// order within the 32 bit values are
+// --------------
+// b3, b2, b1, b0
+//     w1,     w0
+
+#define pgm_read_byte(addr) 		                                           \
+(__extension__({                                                               \
+    PGM_P __local = (PGM_P)(addr);  /* isolate varible for macro expansion */         \
+    ptrdiff_t __offset = ((uint32_t)__local & 0x00000003); /* byte aligned mask */            \
+    const uint32_t* __addr32 = reinterpret_cast<const uint32_t*>(reinterpret_cast<const uint8_t*>(__local)-__offset);   \
+    uint8_t __result = ((*__addr32) >> (__offset * 8));                        \
+    __result;                                                                  \
+}))
+
+#define pgm_read_word(addr) 		                                           \
+(__extension__({                                                               \
+    PGM_P __local = (PGM_P)(addr); /* isolate varible for macro expansion */          \
+    ptrdiff_t __offset = ((uint32_t)__local & 0x00000002);   /* word aligned mask */          \
+    const uint32_t* __addr32 = reinterpret_cast<const uint32_t*>(reinterpret_cast<const uint8_t*>(__local) - __offset); \
+    uint16_t __result = ((*__addr32) >> (__offset * 8));                       \
+    __result;                                                                  \
+}))	
+
+#define pgm_read_dword(addr) 		(*reinterpret_cast<const uint32_t*>(addr))
+#define pgm_read_float(addr) 		(*reinterpret_cast<const float*>(addr))
 
 #define pgm_read_byte_near(addr) 	pgm_read_byte(addr)
 #define pgm_read_word_near(addr) 	pgm_read_word(addr)

libraries/ESP8266WebServer/examples/SDWebServer/SDWebServer.ino

@@ -55,7 +55,6 @@ void returnOK(){
   message += "Access-Control-Allow-Origin: *\r\n";
   message += "\r\n";
   client.print(message);
-  message = 0;
   client.stop();
 }
 
@@ -69,7 +68,6 @@ void returnFail(String msg){
   message += msg;
   message += "\r\n";
   client.print(message);
-  message = 0;
   client.stop();
 }
 
@@ -108,8 +106,8 @@ bool loadFromSdCard(String path){
     head += "\r\nAccess-Control-Allow-Origin: *";
     head += "\r\n\r\n";
     client.print(head);
-    dataType = 0;
+    dataType = String();
-    path = 0;
+    path = String();
     
     uint8_t obuf[WWW_BUF_SIZE];
     
@@ -172,11 +170,11 @@ void deleteRecursive(String path){
       entry.close();
       SD.remove((char *)entryPath.c_str());
     }
-    entryPath = 0;
+    entryPath = String();
     yield();
   }
   SD.rmdir((char *)path.c_str());
-  path = 0;
+  path = String();
   file.close();
 }
 
@@ -186,7 +184,7 @@ void handleDelete(){
   if(path == "/" || !SD.exists((char *)path.c_str())) return returnFail("BAD PATH");
   deleteRecursive(path);
   returnOK();
-  path = 0;
+  path = String();
 }
 
 void handleCreate(){
@@ -203,7 +201,7 @@ void handleCreate(){
     SD.mkdir((char *)path.c_str());
   }
   returnOK();
-  path = 0;
+  path = String();
 }
 
 void printDirectory() {
@@ -211,7 +209,7 @@ void printDirectory() {
   String path = server.arg("dir");
   if(path != "/" && !SD.exists((char *)path.c_str())) return returnFail("BAD PATH");
   File dir = SD.open((char *)path.c_str());
-  path = 0;
+  path = String();
   if(!dir.isDirectory()){
     dir.close();
     return returnFail("NOT DIR");
@@ -242,7 +240,7 @@ void printDirectory() {
  output += "]";
  client.write(output.c_str(), output.length());
  client.stop();
- output = 0;
+ output = String();
 }
 
 void handleNotFound(){

libraries/SPI/SPI.cpp

@@ -308,6 +308,13 @@ void SPIClass::write32(uint32_t data, bool msb) {
     while(SPI1CMD & SPIBUSY) {}
 }
 
+/**
+ * Note:
+ *  data need to be aligned to 32Bit
+ *  or you get an Fatal exception (9)
+ * @param data uint8_t *
+ * @param size uint32_t
+ */
 void SPIClass::writeBytes(uint8_t * data, uint32_t size) {
     while(size) {
         if(size > 64) {
@@ -340,6 +347,15 @@ void SPIClass::writeBytes_(uint8_t * data, uint8_t size) {
     while(SPI1CMD & SPIBUSY) {}
 }
 
+
+/**
+ * Note:
+ *  data need to be aligned to 32Bit
+ *  or you get an Fatal exception (9)
+ * @param data uint8_t *
+ * @param size uint8_t  max for size is 64Byte
+ * @param repeat uint32_t
+ */
 void SPIClass::writePattern(uint8_t * data, uint8_t size, uint32_t repeat) {
     if(size > 64) return; //max Hardware FIFO
 
@@ -376,6 +392,14 @@ void SPIClass::writePattern_(uint8_t * data, uint8_t size, uint8_t repeat) {
     writeBytes(&buffer[0], bytes);
 }
 
+/**
+ * Note:
+ *  in and out need to be aligned to 32Bit
+ *  or you get an Fatal exception (9)
+ * @param out uint8_t *
+ * @param in  uint8_t *
+ * @param size uint32_t
+ */
 void SPIClass::transferBytes(uint8_t * out, uint8_t * in, uint32_t size) {
     while(size) {
         if(size > 64) {