Maxim Integrated acquired Dallas Semi in 2001, and those 1-Wire devices continue to be produced today with their familiar “DS” part number prefix. As a result, the iButton was never really accepted. Unfortunately, the public was not ready for cashless transactions. The iButton could be used to store cash for small transactions, such as transit systems, parking lots and vending machines. Once the technology was proven, the usefulness expanded to include data storage, temperature sensing and other functions. Like fingerprint identification, iButtons ( Figure 1) were built into rings, tags and other personal items that could be carried around and used to identify a particular person or item. The communication identified any iButton as a specific, 48-bit ID number. Manufactured in a tin can the size of a large Li-Ion coin cell, the iButton used a 1-Wire protocol for communication via a single I/O pin. The Dallas Semi brand began with communications and mixed-signal products introduced in the 1980s. Let’s begin back before Maxim acquired Dallas Semiconductor. And, as I learned from this project, there are circumstances where the power gleaned over the same control wire can be insufficient, in some cases requiring a few special manipulations. It’s a slight misnomer, because as in most circuits, a ground (return) wire is also required.
![diy scratchpad diy scratchpad](https://www.kitchentableclassroom.com/wp-content/uploads/2019/05/simple-mandala-mandalas-for-kids-scratch-art-5-683x1024.png)
Not to be confused with PoE (Power over Ethernet), Maxim Integrated’s 1-Wire protocol handles power and access over the same wire.