I'm trying to come up with what should be a fairly simple circuit, but I've been out of the loop with the game for a few years.

I'm trying to connect a double-chest with 2 separate hoppers underneath it to my sugarcane farm. One of the hoppers will lead off to storage while the other is taken away to a composter. What I am aiming for is the hoppers being locked until the double-chest fills entirely with items (stack of 64 in every slot), and then unlock and remain unlocked until the chest is completely empty. Once empty, the hoppers lock again to repeat the cycle.

Reason for wanting to do this is an even 1:1 distribution of the sugarcane between the 2 hopper lines. I have tried using a comparator with a redstone line of 15 signal strength to unlock the hoppers when the chest is full, but as anyone (including myself) might guess, as soon as the chest loses a single item, the circuit relocks the hoppers. I've also tried using a NOT empty approach, with a comparator coming out of the chest, into a block with a torch on it, into the line locking the hoppers. However, there's two things that happen. Either collecting a single item into the chest changes the state of the comparator and unlocks the hoppers, or trying to invert the signal and lock the hoppers as soon as an item enters the chest. This should work, if it weren't for the fact that the hoppers grab the item out of the chest too quickly for the signal to fire.

So the only thing I can think is for the hoppers to be locked until the chest is full, then unlocking, remembering the state of this "full" signal until the chest is empty, then relocking the hoppers. The logic seems right to me, it's just the process of converting that logic into a circuit that I'm needing help with.

[[[ EDIT - SOLUTION FOUND ]]]

Okay, so after considering quite a few suggestions, I have come up with a circuit that works.

A comparator coming off either side of the chests. 1 comparator takes the signal strength of 15, while the other takes an inverted signal (comparator > block with torch > repeater set at full tick delay) and feeding them both into a hopper dropper T flip-flop.

The repeater at full delay is necessary otherwise the inverted signal fires too fast, relocking the hoppers with an item/items in them, that didn't get passed on to the 2 output lines. This can cause an unnecessary backup.

I will be expanding the circuit over to my sugarcane farm to take the first pulse of the t-flip flop to remove power from the minecarts collecting under the farm. This is necessary as with a big farm, the chest can fill back up quickly, giving another 15 strength signal before the chest is empty, re-activating the T flip-flop.

Thanks everyone and hopefully this post gives some people other ideas on things that can be done with this circuit.