This example shows how the imp API's nv table is used to preserve a single value across periodic deep sleeps.

datapersist.device.nut

// On wake from deep sleep or cold boot, Squirrel starts here

// Check if nv table doesn't exist or, if it does, whether it lacks the key 'count'
if (!("nv" in getroottable()) || !("count" in nv)) {
    // Either the nv table hasn't been instantiated or it has but lacks a 'count' slot,
    // so create them. If nv table exists, this code just adds 'count' to it. If nv
    // doesn't exist yet, impOS will automatically create it when we add 'count'
    nv <- { "count": 0 };
}
 
// Do some work...
 
// Increment the value of 'count' and log the result
nv.count++;
server.log("Device code pass: " + nv.count);
 
// Go to deep sleep for 10 seconds
imp.onidle(function(){
    server.sleepfor(10.0);
});