Azure Sphere user accessible storage

Question

I'm working on an IoT project and need a definitive answer on the amount of user addressable storage on the Azure Sphere MT 3620 chip. This page here says "Azure Sphere MCUs include a minimum of 4MB of integrated RAM and 16MB of integrated flash memory"; however, when running through the mutable storage tutorial from GitHub, I can only create a file with a size of 64KiB. My questions are: is the 16MB of flash memory accessible for mutable storage? If not, what are the 4MB and 16MB of RAM used for? If 64KiB is the limit, why such a small amount of storage? Finally, do any SDK hooks exist for addressing external storage in a secure manner? I'm not finding any.

Thank you.

-Mark

Answer 1

Hello @Mark Scott Welcome to Microsoft Q&A Platform!,

I hope the below information helps with your initial query.

MT3620 has 16MB of flash and 4 MB of RAM total.

• For high-level apps

1MB Flash for customer app binary
64kb Flash for mutable storage that the customer app can write/read (e.g. to permanently save data across reboots)
256KB of user RAM for the customer app

• For RT apps

192kb per core to store application binary
64kb of ram per core
RT apps can't use flash
There are 2 RT cores, hence customers can use twice the above for RT Core

The rest of the flash and RAM is used for OS and not available for customer applications.

You may have already referred to this document: Memory available on Azure Sphere

Please let us know by commenting below if you need further help/clarification in this regard.