Re: connection betweem MicroController( pic 16f877a) & m
Hi Jade,
The max 232 is a level converter. A micro doesn't output a negative voltage, and the voltage rails of most micros are less than 5 volts. RS232, on the other hand, uses a voltage swing of +12 - 15 volts to -12 - 15 volts. The max increases the voltage put out by the microcontroller to a level which can be read by an rs232 device (like a PC, or in your case, a phone.) The max 232 chip uses electrolytic caps, but there are versions of the chip which work with standard 'mono' 104 caps, as well as the max233, which needs no external capacitors. You can also realize such voltage shifter with individual components, but with the max so easy to use, why not go with it?
The max chips are available in surface mount, if you want to keep your circuit board size small.
I hope this helps you, and if you have any further questions, just ask, and I'll try to answer.
Best wishes,
Robert