DS1990A: An Authentication and Data Storage Solution that Balances Efficiency and Security
19 December 2023
Ⅱ. Overview of DS1990A iButton
Ⅲ. Functional block diagram of DS1990A
Ⅳ. Where is DS1990A iButton used?
Ⅴ. How does DS1990A communicate with the host device?
Ⅵ. Specifications of DS1990A iButton
Ⅶ. How to use iButton and computer or microcontroller to read the 64-bit identification code?
iButton stands for information button. The information button is similar to the microchip in a smart card, but its placement is more unique. It is placed in a round stainless steel button with a size of 17.35mm x 3.1mm to 5.89mm. The uniqueness of this microchip is that the size varies depending on its function. Its main purpose is to provide the necessary information and data to the equipment facilities in those demanding and harsh working environments.
The iButton is a computer chip encased in a 16mm thick stainless steel case. Its uniquely ruggedized housing allows it to carry up-to-the-minute information to wherever it travels with people and target objects. In fact, because the steel iButton housing is rugged enough to withstand the rigors of indoor or outdoor environments, the iButton can be mounted virtually anywhere. iButton is small and lightweight, and can be attached to key chains, ring bands, watches, or other personal items. Due to its versatility, it is ideal for use in everyday life to control access to such things as buildings, computers, asset management, and various data records.
DS1990A is an iButton tag produced by Dallas Semiconductor (now Maxim Integrated). It is a kind of sturdy data carrier, can be used as the automatic diagnosis system electronic registration number. DS1990A consists of the factory laser processing 64 bits ROM, which includes the unique 48 bits serial number, the 8 bits CRC and the 8 bits series code. Data is transmitted using the 1-Wire® protocol using only one signal lead and ground loop. Each DS1990A contains a factory-engraved 64-bit ROM that guarantees absolute traceability. Its ruggedized package is resistant to harsh environments such as dust, moisture, and vibration, and the DS1990A's compact button form factor makes it easy to use by self-aligning with its mating read/write head. A variety of attachments allow it to be mounted on any object, such as various containers, trays, bags, etc.
Replacements and equivalents:
• DS1920
• DS1972
• DS1982
• DS1991
The DS1990A iButton's block diagram encompasses an internal circuit featuring ROM, functional control, and parasitic power circuitry, comprising parasitic capacitors and rectifiers.
It should be noted that the DS1990A iButton device cannot work alone, so it requires specific accessories to be used in various projects, mainly including the following project accessories:
• DS9101 clip is used to fix iButton.
• DS9092 model probe is used for connection to microcontrollers or circuits.
• DS9490R or DS9490B adapter for connecting iButton to USB port.
The DS1990A iButton exclusively accommodates the address type, allowing for the straightforward retrieval of its 64-bit unique identifier but lacking the capability to perform any write operations. With a swift 5-millisecond read time and adherence to a singular 1-wire communication protocol, the device necessitates direct physical contact by the operator for integration into a project with access restrictions.
Some other applications for the DS1990A iButton include:
• Data collection
• Access control
• Security system
• Inventory control
• Serial data communication
• Identification of products or resources
DS1990A communicates with the host device through wireless communication. The host device sends a request signal to the DS1990A, and the DS1990A responds to the request and returns its unique identification and stored data. The host device determines whether the authentication is successful by comparing the returned identification and stored data with the preset value.
The 1-Wire communication protocol is used between the DS1990A and the host device, which requires only one signal lead and ground loop for data transmission. This communication method has the advantages of simplicity, reliability, and economy, so it has been widely used in many applications.
• Storage temperature: -55°C ~ 125°C
• Operating temperature: -40°C ~ 85°C
• Operating voltage: 2.8V ~ 6V
• Maximum input low voltage: 0.3 volts
• Minimum input high voltage: 2.2 volts
• Minimum recovery time: 1 us
• Maximum data reading time: 15 us
• Input/output sink current: 20 mA
• Typical input load current: 0.25 uA
DS1990A does not provide 64-bit unique identifier. We need a suitable probe or connector to connect it with a microcontroller or computer. In order to connect it to a computer system, it requires the proper hardware and software. Maxim provides adapters and drivers to enable the reading and writing of data. The DS1990A iButton connects to a 1-wire adapter through the DS9490R USB adapter, which in turn connects to the host PC. Maxim is now releasing an upgraded version of this connector, which includes space to plug in and space to insert and accommodate the iButton. To read the iButton, the computer system should have the driver, OneWireViewer software, and a Java JRE installed, which is perfectly compatible with almost all Windows operating systems.
Frequently Asked Questions
1. How does DS1990A communicate?
DS1990A communicates using the 1-Wire protocol, a serial communication protocol that allows multiple devices to be connected on a single bus.
2. What is the code of the iButton?
The two digits on the right (01) are the family code of the iButton. With that the type can be identified. The two left-sided digits (90) are the checksum of the serial number and the family code. The digit sequence in the middle (00001BF2743A) is the serial number of the iButton.
3. How does iButton work?
An iButton device uses its stainless steel 'can' as an electronic communications interface. Each can has a data contact, called the 'lid', and a ground contact, called the 'base'. Each of these contacts is connected to the silicon chip inside.
4. How can I interface with the DS1990A using a microcontroller?
If you're working on a project involving the DS1990A, you might want to know about the methods and protocols for communicating with it using a microcontroller.
