Accumulator

Let’s make a device which helps us in adding numbers. We will learn how to memorize values and update them.

The XOD standard library contains a buffer node which memorizes the input value when it receives a pulse.

To make some calculations and apply them to a stored value we should make a loop from the buffer output to the calculations and back to the buffer input.

To avoid limitless calculations and make it possible to reset the buffer we need a select node. It feeds the calculation result to the buffer node on a pulse.

In this example we’re using the add node, but the calculation may be arbitrary complex.

Exercise #

Examine how the input value and pulses affect the stored result.

1. Upload the program.
2. Change the tweak-number value.
3. Send pulse from the “ADD” node.
4. Repeat the second and third steps a few times.
5. Send pulse from “RESET”.

Replace tweak nodes with a coin acceptor and button to make a ticket system or photo booth.