max485 problem with comm

[sherazi]

regards ...
i made this circuit [plz consider just the max485 only ...but when i used it it didn't received any thing although transmission was all good, then i tried some debugging and found that on removing r14,r15,and r18 it works..
although i get a character y' all the time when i change from transmission to reception ...

plz help me why i get this..

**broken link removed**

 

[ashokok]

i think you are using avr chip. have you enabled internal Pull up on RXD Port??(PD0).external pull up will help in electrical noise condition.
The Value of r14,r15,and r18 near RS485 and other end of RS485 the circuit same??.


P.Ashok Kumar