Wpływ niskich temperatur na szeregową transmisję danych w systemach pomiarowych z mikrokontrolerem ATmega16A

摘要

The paper presents a problem of the serial transmission between blocks of measurement system that works at different temperature ranges. There is also discussed the communication of system controller with ATmega16A device within data acquisition path (Fig. 1). In the paper the results of clock signal frequency tests conducted for internal RC oscillator of ATmega16A microcontroller at low temperatures with the lowest point at 77 K, are also presented (Fig. 2). Here are also considered conditions of effective asynchronous data transmission when USART module of ATmega16A microcontroller is used, because the USART internal baud rate clock depends on the temperature drift of internal RC oscillator. There are calculated characteristics of baud rate matching coefficient and achieved results are compared with total error and recommended receiver error defined for ATmega16A USART module (Fig. 3, 4). In the paper, the low-temperature characteristics of serial clock frequency (Fig. 5) and byte transmission time (Fig. 6) in SPI module of ATmega16A microcontroller are also presented. Moreover, there are shown the low-temperature characteristics of changes of serial clock frequency (Fig. 7) and data transmission time (Fig. 8) in TWI module of ATmega16A microcontroller. The author formulates conclusions concerning the clocking and the asynchronous and synchronous operational range of USART, SPI and TWI modules of ATmega16A microcontroller on measurement systems working at low temperatures.%W pracy opisano problem cieplnych zmian szybkości transmisji szeregowej w bloku akwizycji danych systemu pomiarowego. Zaprezentowano wyniki badań oscylatora RC mikrokontrolera ATmega16A dla temperatur zmniejszanych do 77 K. Przedstawiono charakterystyki współczynnika dopasowania szybkości transmisji asynchronicznej oraz charakterystyki częstotliwości zegarowych i czasów transferu danych dla transmisji synchronicznej w systemach pomiarowych z układem ATmega16A, pracujących w zakresie niskich temperatur.