Data Acquisition made with microcontroller on the 1-wire line

Abstract

Our research aimed at exploring the possibility of the communication between the microcontroller and the 1-Wire device. After receiving communication data transfer, we were to acquire data from numerous 1-Wire devices, such as identification devices, temperature, humidity or other sensors, EEPROM Memory devices etc. Transferring data (and power) through the single line would be much more convenient, providing, that the transfer will be reliable and accurate. In our study we used original testing board with the Microchip PIC 16F628 microcontroller. We also made use of the HP 16 500 A logic analyzer for controlling the waveforms on the 1-Wire bus. The logic analyzer appeared invaluable in testing time waves. 1-Wire devices, made by Maxim/Dallas, have the rich technical documentation. On the base of their Application Note 2420 we prepared an assembler program for the reading the 8-bytes long identification number from the iButton DS1990R. However, obtaining the positive result in performing the communication on the 1-Wire bus appeared to be very hard. In our research we tried to employ as well the intermediate device, namely DS2480B Line Driver. Its role was to relieve the host microcontroller of generating the communication waveforms. It simply took over the role of the host. Also we used the UART channel of the PIC microcontroller. All our efforts, however, remained without any positive result. Then we decided to come back and to connect the iButton to one of free lines on the I/O port of the PIC 16F628 microcontroller. Our choice was line 1 of PORT A, while most of the PORT B lines were dedicated to communicate with the LCD 2x16 display. Positive communication results we achieved, when we adjusted manually the communication parameters, while simultaneously testing on the logic analyzer the resulting waveforms.