通过测试一圈的时间来测算速度，不是测量一秒内的圈速来算速度，实时性强所以使用汇编开发，源码自创请勿用在商业用途。-pass the test circle time to calculate speed, a second measurement is not within the ring speed to the speed count, So real-time-use compilation of development, the source code Inventing Do not use for commercial purposes.