Laser ranging, wire length measurement (phase type) demonstration board hardware + software source code

Phase method ranging: Main control: HC32L136K8 Display: LCD segment code screen Communication: CH340N Serial communication frequency generation: SI5351A Mixing: directly perform AND operation on the two frequency signals, and then go through multi-stage RC to obtain the difference frequency signal (analog circuit No, the parameters are not necessarily the best.) Phase measurement: The microcontroller has a built-in comparator to record the phase of the rising edge or falling edge of the difference frequency signal. An external comparator can also be used to shape the signal into a square wave, which is then measured by the microcontroller. All components Purchased from a treasure store, it is easy to obtain. Because I have not found a suitable laser transmitting and receiving circuit. But for measuring coaxial lines, the length of the network cable seems good. The DEMO board is used to measure the length of the line. The principle is simple and cheap: two frequency signals are needed , each is (A)HZ, (A+a)HZ (the frequency difference is a HZ). After the two frequency signals are mixed, a signal with a frequency difference of a HZ (A)HZ will be generated. After For a length of line to be measured, the phase will change accordingly (0~2pi). When the phase-changed signal is mixed with the (A+a)HZ signal, the phase of a HZ generated will also be shifted by the same phase. It is equivalent to saying The A HZ signal has a phase change due to the line length, which is reflected in the a HZ signal. If A is 1MHZ, the signal period is 1us, and the speed of light is set, the range is 300 meters. Generally, a 32-bit microcontroller can easily count a 10MHZ timer, 360 Degree=1us/0.1us=10. The resolution is 300 meters/10=30 meters. It cannot be used! It is difficult to capture the phase of the signal with a 1us period using a microcontroller. If a is 100HZ, the signal period is 10ms. Generally, a 32-bit microcontroller , easy 10MHZ counting timer, 360 degrees=10ms/0.1us=100000. Resolution 300 meters/100000=3mm.