Zoran Mijanovic

The simple RS232 hub to interface microcontroller peripheral devices with the central processor

A simple interface, which can link up to 32 peripheral devices with the central processor, has been presented in this paper. Peripheral devices can be extremely simple even without a quartz-stable clock. The interface was named RS232 hub. Hub enables that the peripheral devices linked to it simultaneously send and receive data. The peripheral devices are linked to hub with a two-wire line, over which gets power supply and communicates.

The simple multiprocessor communication system

A very simple multiprocessor communication protocol has been presented in this paper. This protocol links a large number of peripheral processors with the central processor. Peripheral processors asynchronously transmit data packages at slightly varied speeds. This is of a particular interest when peripherals are utterly simplified and have no quartz-stable clock. The central processor accepts the data by means of multiplexer. The proposed protocol accepts data of varied speeds with the minimum number of samples per bit. For an undistorted signal, the number of samples per bit is very close to the theoretical minimum.

The identification system for monitoring of teaching activities

The identification system for monitoring of teaching activities has been described in this paper. The system is being used at Faculty of Economics, University of Montenegro. It is RFID based using Mifare contactless cards as identifiers. RF readers are connected to the Ethernet network and all card readings events are stored to central database. The system has no local data buffering. The real time functions and other system functions are clearly separated. Without major changes, the system can be adapted for many other applications.

E-mail script tunneling

The paper proposes a method for synchronizing remote databases with a central database in difficult communication scenarios. Remote points only have occasional access to the Internet, and the central point is protected by a firewall that passes through only basic services, such as HTTP and e-mail. The method consists of using e-mail as a medium for sending shell script and receiving a response/result. High reliability and security of operation are achieved. This method can also be applied to various cases of remote control.

NFC identification system for fuel dispensing control on petrol station

This paper presents the identification system for automation of company petrol stations. The system is based on NFC technology with Mifare 1K contactless cards as identifiers. The system facilitates control and optimizes fuel consumption of company vehicles. It is designed to facilitate recording and control of the process as well as allow filling without the presence of the operator. The system is realized and mounted at the petrol station of the Ministry of the Interior, Republic of Montenegro.

FPGA based capacitive touch pad/interface

This paper reports a sensing principle and FPGA design of a capacitive touch pad/interface where the sensing pad is connected to the I/O pin via an external resistor. The circuit transforms the change in pad capacitance into voltage amplitude during charging, discharging and sharing phases. By using multiple pins and resistors, a multipad system is achieved. The sensing algorithm is implemented in VHDL code. The read-out cycle is parallel and short, what results in a high noise immunity in low frequency range. The silicon/hardware requirements are minimal. The interface can be easily embedded into a system-onchip and used for human-machine, bio-chemical and mechanical sensor interfacing.

The simple microcontroller based capacitive sensor with screen

In this paper the simple microcontroller capacitive sensor is proposed. The sense oscillator is build around internal comparator with few external resistors. The output overload protection is achieved with collector voltage detection. By adding one transistor and screen behind sensing surface, increasing sensitivity and wider usage area are achieved.

Optimal resistor ratio in the DAC with low precision resistors

The widely used digital-analog converter is the one with 2R/R ladder circuit. It can be easy realized as an integrated circuit, but accurate input-output characteristic require extremely precise resistors. With the laser trimming technology it is possible to improve converter accuracy, but aging and environmental factors decrease linearity and overall accuracy of a converter, thus reducing the usable life and the converter applicability. We propose a new DAC design based on 2R/sup +//R ladder circuit, where a high precision is obtained due to better coverage of analog range at the transfer characteristic (even for low precision resistors, ex. 1%, 2% and 5% resistor tolerance). Statistical method shows that various allowed tolerances of the circuit resistors are associated with various optimal resistor ratios in an 2R/sup +//R circuit.