This is an EEPROM replacement based on MCU's internal Flash memory.
The NVRAM class is designed to be stateless. Each operation is
written to flash immediately.

The last 16k(nRF51)/32k(nRF52) of Flash memory are managed by the
VirtualPage class.  This class allows writing a single emulated 4k
page up 40,000 times.

The NVRAM class is a log based byte-wise storage allowing up to
40,000,000 writes depending on the number of used addresses.  Each
four allocated addresses from the beginning of the NVRAM reduce the
write log by one.

When first 256 bytes of the emulated storage are used, there is an
average writing capacity of 145,000 cycles per byte.

When the write log is full, the NVRAM is compressed into a new flash
page. After a new page is ready, the old page is released. This
process can take up to 4500 ms and cannot be interrupted.

The NVRAM functionality can easily be ported to ESP8266 or SAMD by
providing a Flash interface.

This is the support of the Nordic Semiconductor NRF51 (nrf51822,
nrf51422) and NRF52 (nrf52832) platform. Based on arduino-nRF5
(https://github.com/sandeepmistry/arduino-nRF5).

The included radio driver is compatible with the NRF24 devices.
Using a SoftDevice (BLE)is not supported and must be removed before
flashing MySensors with a "mass_erase" operation.