The Research And Implementation Of The Eight-Channel Digital Frequency Measurement System Based On FPGA And CAN Bus

As one of the most important measurement technique in electrocial field, the frequency measurement is used very widely. Because the frequency signal has strong anti-jamming ability and is easy to transmit, the precision of the frequency measurement is very satisfying.At present, many high-precision frequency measurement systems use singlechips and high speed counters. But that design has some drawbacks such as the low-integrity of the PCB, the large size of the PCB, the long signal route, which result in the difficulty of increasing the counter's work frequency. Moreover, the low-integrity of the PCB causes that the high frequency signal would tend to be influenced by outside noise. Consequently, the measure precision is low.This paper explains another method to measure the frequency. The method that can improve measurement's precision and speed is using programmable logic device (PLD) to achieve that function. That design making good use of the PLD's high-integrity strongpoint integrates eight channel signal frequency measurement into one FPGA chip, which has many merits such as high-integrity, wide measurement range, high reliability and so on. The theory of the frequency measurement in this paper is based on traditional cycle measurement method. The system divides the whole measurement range into some sub-range according to decuple frequency, and it can select measurement range automatically. So the measurement precision improves largely.The marine type electrocial manufacture (Eight-Channel Digital Frequency Measurement System) is developed using Altera Cyclone FPGA chip EP1C3T144C8 and Philips ARM micro-controller LPC2129. The system can achieve high-precision real-time Frequency Measurement of Eight-Channe, and transmit measurement result to other instruments if necessary. As one of many electronic instruments on a ship, this system connects with other electronic device throuth CAN bus, and communicate with others following CANopen protocol. The FPGA chip achieves the measurement function, and the ARM chip fulfills the communication and basic control function.