2个PIC之间的通信没有通信线

你好，首先我很抱歉我的“正常”英语。我可能会犯一些错误……我正在开发一个学校项目，我有2个不同的模块，在不同的位置（60cm距离）。第一个模块有一个12F1572处理器，一个12伏特的电源输入，一个78L05电压调节器来为处理器供电。该处理器分析传感器并确定0, 1, 2或3的危险水平。这是一个非常简单的项目，但是这个第一个模块必须与第二个模块通信“危险级别”。这个第二个模块还有一个12F1572处理器和各种LED。这个模块只能有2根导线。所以，只有2根导线，我必须为系统供电，并在处理器之间进行简单的通信。我现在的想法是：第一个模块，根据“危险级别”将切换不同的电压电平来为第二个模块供电。第二个模块只有2个。电线。第一根导线是接地的。第二线是一个可变电压电源输入，连接到78L05总是有5伏的PIC。在这个PIC和使用一个分压器和ADC，I可以很容易地测量输入电压，这样第二个模块知道“危险水平”。对于第一个模块从不同的电压电平切换，我正在考虑使用MUX或DEMUX和许多晶体管来完成这项工作。是否有任何IC可以减少我的硬件或其他想法切换到不同的电压水平？对于PIC的通信而言，这个项目有什么更好的主意？非常感谢你的帮助。



      以下为原文

    Hello,
First I am sorry for my "normal" English.  I might make some mistakes...
I am developing a school project and I have 2 different modules, on different locations (60cm distance).
First module has a 12F1572 processor,  a 12 Volt power input, a 78L05 voltage regulator to power the processor. This processor analyzes a sensor and determines the danger level of 0, 1, 2 or 3.  This is a very simple project.
However this first module must communicate the "danger level" with a second module.
This second module also has a 12F1572 processor and various LED´s inside.  This module can only have 2 wires.
So, with only 2 wires I must power the system and make a simple communication between the processors.

My idea for now is:
The first module, according with the "danger level" will switch a different voltage level to power the second module.
The second module only has 2 wires. First wire is ground. Second wire is a variable voltage power input that connect to a 78L05 to always have 5 Volts for the PIC. In this PIC and using a voltage divider and ADC I can easily measure the input voltage and this way the second module knows the "danger level".

For the first module to switch from different voltage levels, I am thinking about using a Mux or DeMux and many transistors to make this work.  Is there any IC that will reduce my harware or any other ideas to switch from different voltage levels ?

Any better idea for this project in terms of communication between PIC´s  ?

Many thanks for your help.