Retained memory

Enabling backup RAM (SRAM)

• On Gen 3 devices (B-Series SoM, Boron, Argon, Tracker SoM, Tracker One, E404X), retained memory is always enabled, regardless of the feature flag.

• On the P2, Photon 2, and Tracker M (RTL872x), retained memory has limited support in Device OS 5.3.1 and later. See Retained memory for the cases in which it is saved. It is not supported in earlier versions.

• On Gen 2 devices (E-Series, Photon, P1), backup RAM is disabled by default, since it does require some maintenance power which may not be desired on some low-powered projects. Backup RAM consumes roughly 5uA or less on VIN and 9uA or less on VBAT.

Backup RAM is enabled with this code in setup():

void setup() 
{
  System.enableFeature(FEATURE_RETAINED_MEMORY));
}