The signal processor of the DSP platform is generally just a sub-part of the entire system dedicated to the signal processing algorithm. It does not need to control too many peripherals, and in order to meet the real-time signal processing, try to use the linear program structure of the front and back desktop.
The signal processor of this design hopes to form a complete portable radar system with him as the main body. In addition to the signal processing tasks, sampling, display, communication and other tasks must also be completed by him, which needs to meet real-time multi-tasking. Requirements, so you must use an embedded real-time operating system. This article mainly introduces why the real-time operating system is used and the overall software design ideas and solutions based on the DSP / BIOS II real-time operating system.
1. Overall hardware design
This signal processor uses TMS320C5509 as the core of the entire system. Because it considers that the image cache needs a larger storage space, it expands Samsung's 16 Mb SDRAM-KM416S1020C as an expansion memory. The work flow of the entire system is that the controller and D / A provide the signals required by the front-end sampling head, and start the A / D to sample the analog signal from the sampling head. After receiving the DSP, the corresponding signal processing is performed according to the keyboard. The setting will display the image on the color graphic liquid crystal according to certain requirements, and transfer the data to the PC through the USB interface for storage for further processing and display. The overall hardware block diagram is shown in Figure 1.
The TMS320C5509 digital signal processor is a new one in the Texas Instruments TMS320C5000 series, which greatly reduces power consumption and reaches the level of only 0.05 mW per MIPS. Compared with the mainstream product TMS320C54x on the market, Power consumption has been reduced by 6 times. The core of TMS320C5509 is developed from TMS320C54x, so it can be fully compatible with the instructions of the current mainstream TMS320C54x series processors, which not only protects users' investment in software, but also makes software personnel familiar with TMS320C54x programming hardly need to learn He can write his software. At the same time, TMS320C5509 also integrates a large number of on-chip peripherals such as AD, USB controller, etc., making it a SOC (system-on-chip) processor, users only need to add few auxiliary devices to form a A more complete DSP system. As can be seen from the above characteristics, TMS320C5509 is very suitable for application in portable systems.
2. Brief introduction of real-time operating system DSP / BIOSâ…¡
TI's DSP / BIOS II is an embedded real-time multitasking operating system designed specifically for TI's TMS320 series DSP chips. It is mainly composed of 5 parts:
(1) Thread and scheduling (Procedure and Scheduling)
DSP / BIOS II provides 4 different execution threads, including HWI (hard interrupt task), SWI (soft interrupt task) and TSK (task), etc. Each type of thread has different execution, suspend, sleep and other characteristics. DSP / BIOSâ…¡ supports the scheduling method based on static priority, and can provide preemptive multitasking service by modifying the kernel.
(2) Hardware abstraction (Hardware AbstracTIon)
He provides two data transmission modes, PIP and SIO, which can facilitate data exchange between DSP and peripherals. Pipe (data pipeline) uses less memory, and the transmission speed is fast and efficient. SIO (streaming) has a higher abstraction of memory, which is convenient for creating a more structured method of device drivers.
(3) Resource management (Resoure Management)
The specific hardware part can be accessed and configured by using the logical interface of DSP / BIOSâ…¡. DSP / BIOSâ…¡ can not only define the memory map and interrupt vector table through its setting tool, but also set hardware devices such as timers and serial ports.
(4) Communication and Synchronization
DSP / BIOSâ…¡ supports multiple internal thread communication and synchronization methods such as semaphores, mailboxes and data queues. The semaphore is the most important synchronization method, which allows tasks to run and suspend through the semaphore, and can also use mutually exclusive semaphores to manage buffers and devices.
(5) Real-time analysis (Real-Time Analysis)
Real-time analysis tools enable developers to interact and diagnose DSPs during program execution. DSP / BIOSâ…¡ not only provides common log (LOG), STS, TRC modules, but also provides a variety of more convenient debugging and observation tools such as CPU load graph (CPULoad Graph), execution graph (Execution Graph).
3. Software structure design based on DSP / BIOSâ…¡ real-time operating system
The first step in using DSP / BIOSâ…¡ to do a project is to divide the module, that is, split the function to be completed into several relatively independent threads to complete (it can be considered that the thread is exclusive to DSP at runtime), according to the thread The situation of hardware resources considers what type of thread is used to complete. In general, tasks using hard interrupts are placed in HWI to complete, and tasks using timers can be placed in PRD (Periodic Task) to complete. Then is to determine the relationship between the threads, according to him to set the priority of each thread, and how to communicate and exchange data. Banner language is the most convenient method of communication.
The signal processing process of the ground penetrating radar signal processor: A / D sends a hard interrupt signal to the DSP after each column of data is collected, and after each column of data is received, the DSP performs average filtering and adaptive filtering on this column of data respectively. Column counting; when the column counting reaches a frame, wavelet denoising and pulse compression are performed on the image signal of this frame, and finally the image is displayed on the graphic LCD according to the settings of the keyboard and sent to the PC host through the USB interface. For the next step.
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