Design And Implementation Of Micro-controller Circuit And DDS System In Copper Resistance Tester

This paper focuses on the core component of copper resistance tester. It includesmicro-controller circuit and DDS module based on FPGA.The paper has completed the overall structure design of the resistance testersystem. It includes the use of Philips’32-bit ARM7micro-controller, DDS modulebased on FPGA, keyboard input and display module. With the keyboard and LCD, setthe measurement conditions of measured resistance and delivery it to micro-controllerthen storage it. Micro-controller issued commands to DDS module through the SPI bus,the output sine wave signal synthesis of direct digital frequency from FPGA control ofthe constant current source circuit of resistance measurement part.The paper has completed the hardware and software design and implementationof the micro-controller, keyboard input and display module. Focus on and complete thecircuit design of DDS module which is the core part of the resistance tester system.Using hardware description language completed the design of the phase accumulator,lookup table ROM, D/A converters and low-pass filter of DDS system. in the design ofthe phase accumulator, to improve the processing speed, the adder using four assemblyline techniques, and put the high10bits of the result as the address to the look-up table;the look-up table ROM using the symmetry of waveforms only storage the date of thefirst quarter cycle, it can enlarge the data information, and the data in other quartersshould be address-changed; the waveform selector is used to choose the waveform thathas been selected; and in the D/A part, using DAC908who has a high speed; thelow-pass filter choosing sever order elliptic filter.The paper has completed the function modules except the custom resistor circuitin copper resistance tester, has achieved the micro-controller and DDS modules. It haslaid a good foundation for the copper resistance tester’s research.