Electroencephalogram EEG (Electroencephalogram) is a weak low frequency physiological signal. It is a spontaneous potential activity generated by brain nerve activity, contains a very rich information on brain activity, and is an important method for the diagnosis of clinical brain diseases. Therefore, it is of great practical significance to obtain EEG signals. Most of the current EEG signal acquisition systems use a single-chip microcomputer as a controller. Since the EEG signal is a millivolt or microvolt signal, the accuracy is low. According to the characteristics of EEG signals, the analog signals collected by the electrodes are signal-conditioned, and the FPGA chip EP2C8Q208C8 is used to control the conversion of AD574A. The hardware connection circuit and software implementation are given, and the simulation is verified in Quartus II9.0. Thereby improving the reliability and versatility of the system, and having practical application reference value.
Second, an overview of the EEG signal acquisition systemEEG signal monitoring has certain application value in clinical disease diagnosis. The system first uses the electrode to obtain the electrical signal of the cerebral cortex, and then processes it through the signal conditioning circuit, then uses the FPGA as the core to control the AD574A for analog-to-digital conversion and storage. Finally, the algorithm further analyzes the acquired signal and implements the algorithm with the host computer. Communication enables online monitoring. The structural block diagram of the system is shown in Figure 1.
The hardware circuit of the system includes signal amplification and filtering circuit, A/D conversion circuit, FPGA control circuit, FPGA and PC communication circuit. This article mainly introduces the sampling process using FPGA to control AD574A.
1. Introduction to AD574AAD574A is a high-speed 12-bit successive comparison analog-to-digital converter. It is introduced by AD Company of the United States. It has a built-in hybrid integrated conversion chip. It has the advantages of less external components, low power consumption, high precision, and also has automatic zero calibration. Polarity conversion function. Its main characteristics are: resolution 12 bits; nonlinear error less than ± 1/2LBS or ± 1LBS; conversion time 25μs; analog input voltage is 0~10V, 1~20V, 0~±10V and 0~±5V The power supply voltage is ±15V and 15V; the data output is 12 or 8 bits; it can work in both full speed and single mode.
The logic control truth table and working timing diagram of AD574A are shown in Table 1 and Figure 2, respectively. The chart shows that the AD574A's working process includes: starting conversion and reading data.
When starting the conversion, the shilling CS/=0, CE=1, take 1 or 0 according to the number of bits A0 to be converted, and then let R/C=0, the conversion starts. When the conversion is completed, the STS changes from a high level to a low level. By reading the state of the STS, it is judged whether or not the conversion is completed. When data is output, first determine whether it is connected to high level or low level according to the way of outputting data; then let CE=1, CS/=1, R/C=1, and determine the value of A0. If 12-bit data is output twice, when A0 is 0, the output is 8 bits high. When A0 is 1, the output is 4 bits low. If it is 12-bit parallel output, A is arbitrary.
Intelligent charging logo and fast charging: This 100 port USB charger automatically identifies the current signal and performs the current output according to the device restriction. The device is limited to intelligent and secure. Just plug in, no driver or software is required. The latest generation of USB hub controller, the maximum charging output of each USB port 3.5A. Single -port supports fast charging to save your time and energy. 100 % security charging: This 100 port USB charging station built -in smart chip is to prevent voltage from exceeding the current and overload. Reasonable cooling holes can effectively dissipate heat to prevent excessive excessiveness. Excessive charging protection, when these devices are fully charged, they will automatically convert to small charges flowing current, and the battery saturation rate is 99 %.
100 Port Usb Charger,100 Port Usb Wall Charger,Multi Port Usb Hub Charger,100 Port Usb Charging Station
shenzhen ns-idae technology co.,ltd , https://www.szbestchargers.com