# Wireless Data Acquisition System with Feedback Function
## 2 Materials and Methods
### Description of the Receiving Part of the Data Acquisition System  
To organize the collection of data from several sensors in accordance with the concept formulated in Section 2.2, a full-function single-board receiver with a built-in IR request pulse generator, a real-time clock, and an informative 4-line liquid crystal display (LCD) of 20 characters was developed and manufactured in line. The block diagram of the DAS receiver is shown in Figure 10 in black. Blue shows the connection of external equipment for recording received data, while red shows the hardware resources included in the MCU platform and personal computer. The green color shows the connection of the programmer, which is necessary only during program debugging. The designations in Figure 10 are as follows: RRX--data receiver radio module, RTC--real-time clock, GB--backup battery of RTC, CDU--control and display unit, Arduino nano--microcontroller platform based on the Atmega328P MCU, Soft.RX.pin--MCU pin, on which an additional UART data input is organized in the software, INT1--MCU-level interrupt input, configured to trigger on the falling edge of the Int signal with the RTC, CA--current amplifier, FPSU--IR flash power setting unit, IR-LED--infrared LED, PC--personal computer, and USB.1 and USB.2--USB ports of a PC with virtual Com ports organized on them. A simplified algorithm of the program that controls the operation of the DAS receiver is shown in Figure 11.  
In Figure 11, in order to increase the readability of the block diagram of the algorithm, auxiliary functions and actions in interrupts are not shown. For the same purpose, the exit and entry points of the lines indicating connections between blocks are marked as \"A\" and \"B\". The use of marks allows one to reduce the number of lines in the drawing and avoid their intersection. The appearance of the finished DAS receiver, designed and programmed by the authors, is shown in Figure 12.  
In addition to the LCD 20 \(\times\) 4, the control and indication unit contains two more buttons and two LEDs. The button on the board is designed to turn on/off the mode of generating IR pulses for polling sensors, and the button on the Arduino is used to restart the MCU. The red LED indicates single data reception errors, if any, and the blue is used to turn on/off the mode of generating IR pulses for polling sensors. On the LCD indicator, the symbols \"!\" and \"'...\" are displayed before the abbreviated designations of the sensors (D1, D2, D3, D4), and \"Lo\" after them. The symbol \"!\" before the sensor number means that  
Figure 10: DAS receiver block diagram and equipment connection diagram on receiving side. the voltage measured by it is less than the minimum permissible by the manufacturer for this battery; the symbol \"\({}^{\star}\)\" means that the measured voltage is greater than the maximum permissible for this battery. The abbreviation \"Lo\" after the sensor number means that the sensor supply voltage is low (Low), less than 3.05 V. If there are no deviations in battery voltages and sensor power supply from the norm, only sensor numbers (D1, D2, D3, D4) are displayed in the top line. The operation of the DAS receiver is explained by a simplified algorithm of the program that controls the operation of the DAS receiver, as shown in Figure 11. After starting the program and configuring the ports, interrupts, RTC, and I2C interface, the software UART is open for receiving radio module signals. The hardware UART-USB available on board the Arduino platform is used for two-way communication with a personal computer. In this case, its input line is used to set the current RTC date and time, and its output line is used to log the operation of the DAS on the computer. After this, the receiver goes into sleep mode. When an interrupt signal is received, generated every second by the RTC chip, the receiver MCU generates an IR code to request a response from the sensor, after which the receiver switches from sleep mode to the mode of detecting the header of the data block sent by the sensor.