基于OpenGL的三维仪表例子，做了一个简单的电压表模型-OpenGL-based 3D Instrumentation example, do a simple voltage meter model

并行接口电压输出型DA转换器的控制，包括清零子程序，转换子程序，完成满值点验证、零值点验证子程序等-Parallel interface voltage output type DA converter control, including Clear Subroutine, conversion routines, the completion of full value point authentication, zero points, such as authentication Sub

串行接口电压输出型DA转换器的控制，包括延时子程序， 送1位数据"1"和"0"子程序， 送1BYTE数据，B通道单独转换，A通道输出任意数等子程序-Serial interface voltage output type DA converter control, including the delay subroutine, send a data 1 and 0 subroutine, send 1BYTE data, B-channel single conversion, A-c