说明：  AVR通过ICL7135的busy引脚采集的源程序。AVR的pwm提供ICL7135的时钟，并通过捕捉busy的宽度获得转换结果。编译环境是GCC-AVR
(the source code of AVR-Mega48，the clock of ICL7135 is generated by M48，and its busy signal is used for the result of conversion by capture is width。)