Memory on Arduino Due

caldicot · July 28, 2018, 8:25am

Hi,

I am a little bit confused about the memory on the due. Maybe someone of you could explain me this behavior.

The Arduino Due has amongst others two memories: Data and Program.
As described here, there is a Flash and SRAM memory.

Flash: 512 KB
SRAM: 96 KB (two banks: 64KB and 32KB)

When uploading a application with PlatformIO the memory usage is shown:
Memory Usage → Redirecting...
DATA: [==== ] 35.3% (used 11580 bytes from 32768 bytes)
PROGRAM: [======= ] 73.6% (used 385844 bytes from 524288 bytes)

I have understood, that the program section contains the application itself - so the code that I’ve written.
In the data section, the running application (the values of variables, etc) are saved.

I was expecting, that the Data portion is bigger?
It has about 32KB, but the SRAM has a total size of 96KB. Are the other 64KB used for other things? Why are they not shown in the memory usage diagram?

ivankravets · July 28, 2018, 7:32pm

You can run pio run -v to see details about memory usage.

See the source code how do we calculate memory usage:

github.com

platformio/platform-atmelsam/blob/develop/builder/main.py#L109:L110


      
                          "$SOURCES",
                          "$TARGET"
                      ]), "Building $TARGET"),
                      suffix=".hex"
                  )
              )
          )
          
          
if not env.get("PIOFRAMEWORK"):
              env.SConscript("frameworks/_bare.py")
          
          
#
          # Target: Build executable and linkable firmware
          #
          
          
if "zephyr" in env.get("PIOFRAMEWORK", []):
              env.SConscript(
                  join(platform.get_package_dir(
                      "framework-zephyr"), "scripts", "platformio", "platformio-build-pre.py"),
                  exports={"env": env}
              )

caldicot · July 29, 2018, 7:54am

Thanks for your reply, Ivan.
I ran pio run -v, but I am afraid this is not answering my question (or I don’t get it).

Basically my question is, why are only ~32KB shown as Data memory, when I would have expected 96KB (as this is the size of the SRAM).

As far as I understand the output of pio run -v it only shows a detailed list which section of the program uses how much memory, right?

ivankravets · July 29, 2018, 6:26pm

Ah… This is our bug and I’ve just fixed it in

You can switch to the latest upstream version via Atmel SAM — PlatformIO latest documentation

Thanks for the report!

caldicot · July 29, 2018, 8:13pm

Thanks, Ivan