Help me with a Max232 to Max485 protocol

[member_tdh]

Hi!

Now, I having a problem with the protocol RS232 to RS485. I posted my schematic and could any body help me check it?

follow this circuit, when I brake pin 9 (MAX232) and connect to VCC or GND, transmit and receive was OK. But I keep intact this pin's connect, I couldn't transmit or receive...:?:

Please help me!

My project was designed: PC (master) <--> AVR (slaver1) <--> AVR (slaver2) throught MAX485.

in the VB6's code: I cann't control the RTS pin.

 

[IanP]

max485 avr

The key factor in the successfull RS232-to-RS485 conversion is in the correct switching between transmission and reception ..
If you can't use RTS signal to control the DE-/RE pins than the whole idea of using MAX232 and MAX485 (including option with MOSFET transistor) won't work ..

Here is another (working!!!) option:

Take a look at it and if you have further questions - come back ..

Regards,
IanP

 

[member_tdh]

max485 schematic

Hi!

Last night, I was check my circuit successfull! both of transmited and received are ok!

I post my shematic below: cut pin 9 (max232), connect to both pins 2,3 (max485) to pin 13 (max232) throught a resister 1k, diode zerne 5v2. Its's OK!

 

[Thanhnh]

max232 max485

i think this can help u.
**broken link removed**
u can use smd components.


Best regard