Freescale's track parameter detection method based on area array CCD

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Summary:

This paper proposes a method to effectively utilize the internal hardware resources of S12 microcontroller and use the area array CCD to detect the path parameters. Ordinary CCD image sensor, working voltage → generally about 12 V, output NTS (' or PAL analog video signal. Use S12 internal A / D converter. And with the synchronization signal from the video signal. The microcontroller can The image signal is directly collected into the internal RAM of the microcontroller. Then the image information is processed by software to obtain various path parameters.

hardware design

The block diagram of the circuit system for capturing video images based on S12 MCU is shown in Figure 3. These include the S12 microcontroller minimum system, the step separation circuit, the 5V regulator circuit, and the 12 V æ–© boosted circuit.

The S12 MCU port is equipped with the following configuration:
(1) AD input port PAD02. Used to input video analog signals;
(2) External interrupt port IRQ. Used to input video line sync signal;
(3) Digital 10-port PM1. Used to input the odd-even field signal;
(4) PWM output port for outputting 12 V chopper boost control signal of PWM2.
Part of the system circuit diagram is shown in Figure 4.

Figure 4 12 V chopper boost circuit

As shown in Figure 5, only the line sync signal and the odd-even field signal are input to the MCU. The video signal can be directly input to the A/D conversion port of the MCU without being blocked by the capacitor.

software design

The software design mainly includes an image acquisition module, an image processing module and a communication module.

The main functions of the image acquisition module include:
(1) Initialization module, mainly responsible for A/D converter initialization and external interrupt initialization;
(2) The external interrupt response module is mainly responsible for determining whether the frame image starts and whether the line image is acquired, and starts A/D conversion, and the marked image is collected;
(3) A/D conversion interrupt response module, which is mainly responsible for collecting a fixed number of image data.