Avr & Max485

Hi,

I am trying my two AVRs to communicate with each other through Max485.
One Avr is Tx and the other is Rx (Simplex mode).Dont need two way communication.But I have some confusions and questions i.e.
1- I can get data on A pin of Max485 connected to Tx Avr.But no data on RO pin on RX Avr.
2- Do i really need B pin to be hooked to B of other Max485.

Power supply is 5V. and i am using separate batteries on each side of Avr and MAX485.
As i dont need two way communication, I have connected RE/DE of U1 to 5V and RE/DE of U4 to GND,for Transmit enable and receive enable respectively.
schematic is attached.

Yes you need B connected. It's a differential driver.

I want to purchase a Avr kit and Universal Progrrammer............. plz send me the price n from where I can buy them

blueroomelectronics said:

Yes you need B connected. It's a differential driver.

Click to expand...

ok thnx.
and wht about RO on the Rx side.Any idea why i am having no data there.coz i have tested with B connected also ?

You're missing the bias resistors.

bias resistor

blueroomelectronics said:

You're missing the bias resistors.

Click to expand...

I am not that expert.can u elaborate which value and where should i connect this resistor.
thnx...

hi all
i want circuite rs485 for avr plz to my mail:

Try R.E.Smith Serial Communications RS485