Dumping memory blocks with the shell

[philj404]

Here's something I added which might be useful. It's a few memory dump commands I added to examples/ArduinoTextInterface.

• eeprom? [<beginHex> [<numBytesHex>]]
• progmem? [<beginHex> [<numBytesHex>]]
• ram? [<beginHex> [<numBytesHex>]]

(note that only AVR processors will support all these commands, as some processors have no EEPROM etc.)

You might use it to see memory leaks over time.

It was particularly useful for me for finding redundant Serial.println("look! more text"); string arrays strings using RAM. Wrapping each instance with the F() macro (e.g. as Serial.println(F("look! more text")); ) freed a lot of RAM .

For example I found some interesting constant strings in PROGMEM:

> progmem? 60 50
60 C 94 E8 3 C 94 E8 3 70 75 6C 6C 75 70 0 6F ........pullup.o
70 75 74 70 75 74 0 69 6E 70 75 74 0 31 0 30 0 utput.input.1.0.
80 68 69 67 68 0 6C 6F 77 0 3A 20 62 61 64 20 61 high.low.: bad a
90 72 67 20 63 6F 75 6E 74 0 76 0 0 0 6F 0 1 rg count.v...o..
A0 0 68 0 2 0 0 0 0 0 20 64 6F 65 73 20 6E .h....... does n

In addition for AVR processors there were some useful hints for internal variables used to manage the stack and heap:

> stackheap?
Unfragmented memory (usable for stack): 1542
Total free memory 1542

> memory?
+----------------+ 256 (__data_start)
+      data      +
+    variables   + size = 56
+----------------+ 312 (__data_end / __bss_start)
+      bss       +
+    variables   + size = 302
+----------------+ 614 (__bss_end / __heap_start)
+      heap      + size = 112
+----------------+ 726 (__brkval if not 0, or __heap_start)
+                +
+                +
+   FREE RAM     + size = 1538
+                +
+                +
+----------------+ 2263 (SP)
+     stack      + size = 40
+----------------+ 2303 (RAMEND / __stack)

The memory? and stackheap? work for AVR microcontrollers, as that is what I needed. You may be able to find a way to do something similar for other architectures. But that's left as an exercise for the student 😁.

Thanks to/further reading:

• https://github.com/Locoduino/MemoryUsage from Thierry Paris
• https://learn.adafruit.com/memories-of-an-arduino/measuring-free-memory from Adafruit
• http://www.avr-developers.com/mm/memoryusage.html from avr-developers.com
• https://playground.arduino.cc/Code/AvailableMemory/
• https://github.com/mpflaga/Arduino-MemoryFree
• https://github.com/Locoduino/MemoryUsage