This post may be of help if sleeping SPI Flash.

I have been using:

//SPI Flash
myFlash.init(T2_WPN_FLASH_SPI_CS);
myFlash.powerDown();

when deep sleeping Whisper sensor nodes.

Recently, I changed one of these to a base node. The new code needed to access the unique ID of the Whisper node using:

for (uint8_t i = 0; i<8;i++){
//uint8_t uniqueID = myFlash.uniqueId;
Serial.print(myFlash.uniqueId, HEX);
}

as per WhisperNodeFactory.ino

I had not realised that the powerDown status was retained by the Whisper node and the setup required:

// SPI Flash
myFlash.init(T2_WPN_FLASH_SPI_CS);
myFlash.powerUp();

to function correctly.