Hand made pl-2303hx USB to TTL level serial port circuit_ Old bear passing by_ Sina blog

                  Handmade pl-2303hx Of USB turn TTL Level serial port circuit

PL-2303hx I bought it for several days , Never dared to do it , The reason is simple ,PL-2303hx This piece of IC It's too small , It is not easy to weld . Look at the drawings tonight , It took half an hour , Finally, the required pins are led out , next step , Make welding components , It's much simpler . All the welding is finished 1 One and a half hours , Plug into the computer usb Interface , One time success . Now to summarize ：

1、 The original serial port of the computer , called RS232 Interface , This is a kind of cmos Interface , The interface voltage is from -15 To +15v Between , And MCU C51 All are TTL level , The level voltage is only 0V or 5V Two kinds of . What you make with this computer is what you use on the single chip computer TTL level , therefore , Don't answer again MAX232 Chip . This is one of its great benefits .

2、 Before making this circuit , I have searched the Internet for several days , I still don't understand that it's appropriate to use that drawing , however , Now I can finally confirm the following picture , It must be available , I did an experiment with a single chip computer , It can be used completely . It's also very fast . Remember this picture , Want to do , But if you can't do it, you can refer to it .

3、 The circuit can extract USB Interface +5V voltage , Just for C51 The use of single chip microcomputer , Very convenient . in addition PL-2303hx It can also provide an external +3.3V The voltage of , This voltage , about AVR Single chip microcomputer , Very suitable .

In circuit ：R8 The actual use is 1K European .R6、R7 What I actually use is 47 European ,C2、C3 Another oscillation capacitor , I'm using 33pF Of , Actually , image C5、C6、C7 These three capacitors , You can also change . It's about the same size , It's not a problem .

After verification, the following circuits are also possible