Abstract: Designed a portable electroencephal wireless acquisition system based on single chip, wireless chip NRF24L01 and TFT LCD display, the system controller adopts STC12C5A60S2 single-chip microcomputer. The microcontroller of the transmitting end collects and stores the pre-treated EMO, and wirelessly transmits wireless transmission through the NRF24L01 chip, and the receiving end microcomputer is sent to the liquid crystal display and perform further analysis. The system does not need to use a PC, so there is a small size, light and low power loss.
0 introduction
EEG (Electroencephalogram) is a weak low-frequency physiological signal. It has a spontaneous potential activity generated by brain neurological activity, which contains very rich brain activity information, and provides data analysis and basis for the diagnosis of brain diseases by recording the eElectronic signal. Epilepsy is caused by abnormal discharge of brain, is a chronic disease and synthetic disorder, and the sudden appearance and short-term central nervous system functional disorders caused by over-discharging of brain neurons [1]. Currently, the epileptic discharge discovery is still an objective basis for the diagnosis of epilepsy and epilepsy.
Due to the conditional restriction, the sample collection of human epilepsy electroencephalter data is relatively difficult, and the data is vulnerable to the interference of the external environment and patient movement. At present, some of the portable EEG collectors are mostly collected by the electroencephals, passing to the PC through the wireless module transmission, and working in the PC, and the PC is multi-desk machine Run under the Windows system. This system has good data capabilities, stable performance, long-term record. However, the entire system generally requires an external power supply, the volume is large, which is generally placed in the institution and hospital, and there is no truly portable use. The relatives of the poor mountainous areas in less medical resources, this difficult-moving medical equipment leads to these regions. Basic medical needs cannot be satisfied.
Therefore, how to make the EEG collector more flexible and convenient when used, and began to get widespread attention. It is important and applied value to design a small size, low power consumption, and can really portally use.
1 Overall structure of portable ecpoion wireless acquisition system
This paper proposes an EEG signal wireless acquisition system based on STC12C5A60S2 microcontroller, wireless chip NRF24L01, and true color liquid crystal display TFT6448BS-5.7. Where the STC12C5A60S2 single-chip microcomputer is responsible for data acquisition and pretreatment, the NRF24L01 module is responsible for data transmission and receiving transmission, and the receiving end STC12C5A60S2 microcomputer will receive the received data through the liquid crystal display TFT6448BS - 5.7. Display. The specific system composition is shown in Figure 1. According to the application characteristics of the portable EEG collection system, it is required to reduce its volume and weight, and real relatively portable.
Figure 1 System function block diagram
1.1 front end collection of EEG signals
Since the main frequency range of the human brain electrical signal is 0.05 to 100 Hz, the amplitude is about 10 to 200 μV, and the signal is very weak. At the same time
Other bioelectric signals are generally mixed, plus 50 Hz power frequency interference, so that the measurement conditions of the electroelectric signal are very complicated. Traditional collected front ends typically improve signal-to-noise ratio of signals by simulating anti-mix filters, multi-stage amplifying circuits, and wave circuits, which can result in a large system of size, inconvenience and power consumption. In order to monitor the clinical mean electromide signals, this paper uses the method in the reference, and its front-end acquisition module selects TI's ADC1299 chip.
1.2 single-chip control module
The microcontroller control module of the system includes a single-chip microcontroller and a receiving end microcontroller of the transmitting end. The sending end microcontroller must have an integrated A / D converter in the film, and the microcontroller of the receiving end must be external to the LCD. Therefore, the powerful STC12C5A60S2 single chip microcomputer is selected. The microcontroller is a new generation of 8051 single-chip microcontrollers in Hongjing Technology. The STC12C5A60S2 series single-chip microcomputer with Hongjing sixth generation encryption technology cannot be decrypted, with strong anti-interference ability, and an internal integration has 8-digit A / D converter, the system The A / D conversion function is used in the medium, so that the system does not need to add A / D conversion chips, and the single-chip speed is fast, high.
The ADC of the STC12C5A60S2 is successively comparative ADC. After power-on, the electroelectric signal passes the electronic switch to control the microcontroller into the transmitting end after the electronic switch is used, and only one-to-pass signal enters. The ADC input channel and P1 port are reuse. After power-on reset, the P1 port is weakly pull-up I / O port, and the port used as ADC can continue to be used as I / O port. The single chip microcomputer converts an analog signal into a digital signal via the ADC while controlling the wireless module to transmit the digital signal of the brain to the receiving end, and enter the real-time display and storage of the signal to the receiving end.
1.3 wireless module
The system employs 2.4 GHz wireless single-chip transmission chip NRF24L01, using FSK modulation, wireless communication of point or 1 pair 6 can be realized. The wireless communication speed can reach 2Mb / s. It has a small size, low power consumption, less external, high rate, and is ideal for wireless transmission applications. The NRF24L01 can be connected by the SPI interface to the microprocessor, complete settings and sending data from this interface. The STC12C5A60S2 single-chip integrated SPI controller, which can be easily set by software settings, which will only output data when you receive this unit, which is convenient to program. The connection diagram of the NRF24L01 and the microcontroller is shown in Figure 2.
Figure 2 Connection diagram of STC12C5A60S2 and NRF24L01
1.4 display section
The display portion is selected from 5.7 inches, the resolution is 640 × 480, and the working voltage is 3.3 / 5V, support 256 colors. Since it is designed for single-chip users, a simple high-speed 8-bit bus is connected to a single-chip microcomputer. This display is low power consumption, and it can also meet portable requirements. The programming of the system includes a single chip program, a liquid crystal display driver. The transmitting end performs A / D transform and wireless transmission by a single chip, and the receiving end receives data by the single chip over NRF24L01, sent to the liquid crystal display.
After receiving the microcontroller, the receiving end microcontroller is transmitted to the liquid crystal display for display, one byte in each point in the display memory, the X, Y coordinate on the display, corresponds to the address of the display memory. Therefore, simply enter the X, Y coordinate can directly read and write the corresponding point data, and do not calculate the address of the pixel point in the display memory. After writing data, the X coordinate automatically adds 1. After writing, it is automatically transferred, and the Y coordinate is automatically added 1. The connection of the single chip microcomputer and the liquid crystal display is shown in Figure 3.
Figure 3 Single chip microcomputer and TFT LCD connection diagram
2 system software design
The system consists of a transmitting end and a receiving end composed of the STC12C5A60S2 microcontroller and the NRF24L01 wireless transceiver chip. The transmitting end performs A / D conversion and wireless transmission through a single chip, and the receiving end receives data through the NRF24L01, and then sent to the STC12C5A60S2 microcontroller for display and analysis. Wireless module NRF24L01 All configuration work is completed through the SPI, a total of 30B configuration words. Generally, Enhanced Shock Bursttm transceiver mode, in this mode of operation, the system's programming is more simple, and stability will be higher. The configuration word of Enhanced Shock BursTTM enables NRF24L01 to process RF protocols. After the configuration is completed, only the contents of the reception mode and the transmission mode can be achieved in the process of working in the NRF24L01. The data flow is shown in Figure 4.
Figure 4 Single chip program flow chart
3 conclusions
This article is designed with an electromalnow signal acquisition and wireless transmission system based on a small size, lightweight and low power consumption. The STC12C5A60S2 single-chip is selected as the main controller, and the NRF24L01, TFT6448BS-5.7 is controlled by the two SPI modules, respectively, and the WiFi wireless transmission and waveform display of the EEG signal is achieved. This system does not need to use the PC, control, and display with a single chip microcomputer. Since it is easy to carry, high integration features, a set of feasible plans can be provided for the diagnosis of eElectronic diseases in the poor mountains of medical resources.
Be
Source: Wiku Electronic Market Network
Our other product:
