interfacing 3.3V and 5V RS232 channels.

[dim912]

Hi..
Hi I am using PIC 18F25J10 whose VDD is 3.3 V and a PIC 16F877A whose VDD is 5.0V. I need to have the RS232
communication between this two devices. But they can't be connected directly, because of their voltage levels are
different.(If i connect --> according to the data sheets RS232 will not work and ports of 3.3 device may burn or reduce its life time).

so can any one please suggest me a way to connect this two devices.

thank you...

 

[IanP]

It's not difficult to connect 3V PIC to 5V PIC directly, using just some resistors and diodes ..
Have a look in:
3V Tips 'n Tricks
https://www.microchip.com/stellent/groups/techpub_sg/documents/devicedoc/en026368.pdf

:wink:
IanP

 

[bigdogguru]

If the both PICs are in close proximity, on the same PCB, you want to use asynchronous serial communications, not RS-232. In which case a level shifter/translator would do the job.

You could either use discrete components or an IC to perform this task:

**broken link removed**

TI, MAXIM, NXP and other manufactures make specific ICs for the job.

BigDog

 

[marius810327]

Hi,

You can also make use of a zener diode circuit on the Tx and Rx Pins. It will do the job.

MN