Nowadays, we acquire the analog signal and digital signal in Electrical Control. We usually use the MCU (51 series, AVR series, PIC series) and DSP is that the amount of data collection is too large, so it’s not able to meet our needs at this time. Now there are many measurements and Control Companies are using FPGA (field programmable logic device) to collect the data. The advantages of FPGA: there are many I / O ports and resources that can be programmed freely, there are many interfaces which is easy to connect.
The main FPGA vendors are Altera and Xilinx. The system use Altera’s FPGA EP1C20F400.
1. System components: FPGA chip area, multiplexer and A/D sampling circuit, clock power, PROM, W5300 network chips and other components.
Figure I Schematic diagram
2. EP1C20F400 analysis and allocation of resources:
The core of the system uses 1.5V, I / O port is 3.3V. And it is divided into four parts
(a) FPGA logic operations: receive information and data from processing.
(b) A/D control: for A/D sampling.
(c) Digital detection: to achieve of the digital output control, storage of digital input, and status of digital input for changing the identification (input interrupt).
(d) Logic Interface: the CPU interface, ease for PCI, VXI and connect to other buses.
3. Analog acquisitions:
The system used is A/D chip AD976A. Quantity of Multiplexer is through AD438 input after switching to the AD976A chips. A / D sampling including: registers, clock generation module, control the sampling state machine, data storage modules.
4. Digital acquisition:
It’s mainly for complete the amount of digital acquisition and storage.
Figure II schematic for digital sampling and storage
5 Ethernet Interface
The system uses a WIZNET W5300 chip for Ethernet communications. W5300 uses a 16-bit bus interface mode.
Figure III W5300 circuit interface
Summary: In the three pillars of the times ASIC, DSP and FPGA. Because FPGA is flexibility, user-friendly, FPGA is outstanding in small and medium high-speed projects. Now, most of the project requires an Ethernet network communication, W5300 integrated a TCP / IP protocol stack for Ethernet communications greatly reduce the workload.
Author:：浩然電子唐海峰
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