If your program never uses malloc(), the formula used in freeMemory() will produce the wrong result. I don't know about the _arm_ implementation, but for the AVR one, it is incomplete for handling the corner case when the program does not use the malloc() function. Return _brkval ? &top - _brkval : &top - _malloc_heap_start įirst, the freeMemory() function that you used from Adafruit was originated from a GitHub repository. #elif defined(CORE_TEENSY) || (ARDUINO > 103 & ARDUINO != 151) should use uinstd.h to define sbrk but Due causes a conflict Now all different methods report a free ram of 2299, including the simple Serial.print(). For example, at the last example (PROGMEM, strcpy_P) when I included another Serial.print(freeMemory()) before the call of the printing functions, then both freeMemory() calls report 2299!Īnother interesting problem is that the freeMemory() reports 2299 as freeRam, while the SRAM of my Arduino Uno is only 2 kbytes.įollowing the suggestion in comments, I changed "test" to "testtesttesttesttesttesttesttesttesttesttesttesttesttesttesttest". Also it would be really useful if you could explain in detail what exactly each of the keywords F(), (PGM_P)F, PSTR, const PROGMEM does.ĭepending on where and how I use the call Serial.print(freeMemory()) the results change. The basic point of this question is to gather all the possible flash memory printing techniques. This call reports free RAM = 2267 Using strcpy_P and const char PROGMEM char buf This call reports free RAM = 2267 Using strcpy_P() char buf This call reports free RAM = 2299 Using sprintf_P() char buf This call reports free RAM = 2267 Using the F() Macro: Serial.print(F("test")) I created a program that prints the word "test", with various methods: Simple print: Serial.print("test") At the same time, I have been using the freeMemory() function from Adafruit. I have been testing various techniques on an Arduino Uno for serial printing from flash memory instead of RAM.
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