Implementation of ISA bus DMA based on Linux

As we all know, vision is the most important way for humans to perceive the world, and all material forms in real life exist objectively in three-dimensional space. 3D display is truly well known. vision is the most important way for humans to perceive the world, and all material forms in real life exist objectively in 3D space. 3D display can truly reproduce the three-dimensional space of the objective world, provide a more consistent way of communication with people's observation habits, and help people make comprehensive use of various deep hints, through the computing perception of the brain, you can obtain a real, rich, and reliable visual experience, which plays an important role in social development and development in science and technology and economy.

Currently, 3D display can be divided into four categories: 3D display, holographic display, three-dimensional display, and three-dimensional display. the principles and features of 3D Display are shown in Table 1.

Table 1 Principles and features of various types of 3D Display

In this paper, a 24x16 two-dimensional LED array is rotated to achieve three-dimensional display with a size of 69120 individual pixels and a space of 9414 X 6618mm bar, this paper discusses the overall structure, display principle and implementation methods of each component of the system. The "teapot" is used as an example to analyze and discuss the 3D Display System.

1. design of LED 3D display system

1.1 Overall solution

Because the human eye has a temporary visual feature, that is, the tracking of brightness changes by human vision lags behind due to the delay of consciousness processing. Based on this feature, a light-emitting diode array driven by a motor is placed on both sides of a symmetric rotating shaft to rotate at high speed and periodically scan a cylindrical space. At the same time, the addressing driving control circuit modulated the light-emitting status of the LED array at different times as needed, so that three-dimensional display can be realized by quickly displaying a two-dimensional image cross section sequence. Because the time for human eye vision is about 50 ~ 100 ms, when the motor speed exceeds 10 R/s, people will not feel flashing, but see three-dimensional images. According to this principle, a three-dimensional LED display system shown in 1 can be designed.

The computer generates three-dimensional data and transmits the data to the memory on the drive board through the data transmission circuit. the angle encoder tests the rotation angle of the motor and sends the signal to FPGA, then, the FPGA drives the LED screen display based on the output signal of the collected angle encoder and refreshes the LED display screen on time. At the same time, the entire rotating drive board quickly rotates under the drive of the motor, quickly display a two-dimensional cross-section image to achieve three-dimensional display.

1.2 3D data generation

Using the powerful functions of Matlab software, we can first use im read (), im f info (), m eshgrid (), m eshc (), and su rf () to implement a three-dimensional image with a gray value, assuming that the obtained three-dimensional image coordinate is P (X0, Y0, Z0 ).

The column coordinate of the LED lamp in the cylindrical space obtained by rotating the LED array is F (r, H, z). according to the conversion relationship between the column coordinate and the Cartesian coordinate, the three-dimensional Cartesian coordinate E (X 1, Y 1, Z 1) of spatial LED lights can be obtained as follows:

Here, r, H, and z are all integers, and there are:-12 <r ≤ 12, 0 <H ≤ 360, 0 <z ≤ 16.

Finally, make D (X2, Y2, Z2) = P (X0, Y0, Z0) lead E (X1, Y1, Z1) obtain the three-dimensional Cartesian coordinates of the displayed l ed lamp as the information source of 3D data.

Since the Matlab 610 version, Mathworks has added the Instrument control toolbox in the software to provide formal support for the serial communication standard of RS2232/RS2485. Therefore, the system uses the serial class of the toolbox and fopen, fw rite and other functions to transmit the obtained 3D image data to the LED driving circuit board through RS2232 serial port and data transmission circuit.

1.3 Data transmission circuit

After using the serial port of RS2232 in the device control box, the 3D image data is transmitted to the rotating LED driver board using the infrared coding and decoding technology. the entire data transmission communication structure is shown.

In the single-chip serial port module, select the level conversion chip maxcompute chip to achieve two-way conversion between TTL level and RS2232 level, so as to transmit three-dimensional image data to the single-chip serial receiving port RXD, then, the MCU sends data through TXD. The modulation and infrared emission modules in the figure are modulated into 38 kHz carrier signals by a multi-harmonic oscillator circuit consisting of N E555 chips. Finally, the infrared emission tube TSAL6238 is used to send out signals in the form of optical pulses. In order to ensure the accuracy of the infrared reception data, the oscillation frequency produced by N E555 should be close to 38 kHz as much as possible. Therefore, when selecting the resistor and capacitor, we should choose precise components and ensure the stability of the power supply voltage.

In the infrared receiving and demodulation module of the data transmission circuit, choose Vishay's TSOP1738. its internal function has included converting the received carrier frequency to 38 kHz pulse-modulated infrared signals into electrical signals, the front amplifier and the automatic gain control circuit are used for amplification. Then, the filter is used for filtering, and the filtered signal is demodulated by the demodulation circuit. Finally, the output-level circuit is used for reverse amplification.

Therefore, you only need to use this infrared receiving module to send its data output directly to FPGA for processing. The experimental results show that the infrared transmission circuit can transmit data at a maximum rate of 1 kB/s.

1.4 angle encoder and motor Module circuit

The three-dimensional display of the system is realized by quickly displaying a series of two-dimensional cross sections in the rotating space. the LED screen is rotated into 180 cross sections every week, that is, the display screen needs to be refreshed every 2 °. In order to accurately refresh the display screen, the angle encoder is used to identify the angle of the display screen. the angle encoder can identify the rotation angle of the motor by testing the motor rotation pulse. The angle encoder model used in this system is zsp201762022g2360b25224e. This encoder can output 360 pulse signals during one week of rotation. In this way, the angle encoder can generate two pulse signals for every 2 ° conversion of the motor. the LED display control system controls the refresh LED screen by counting the output pulse number of the angle encoder.