[SOLVED] sending serial data via optocoupler

[FvM]

TX output high should give RX input high and vice versa. Check in your circuit.

 

[kookooli]

TX output high should give RX input high and vice versa. Check in your circuit.

I'm a little bit confused... Can you send me a schematic ?
this is what datasheet says ...

 

[FvM]

That's what the datasheet shows about signal polarity. Please check with your circuit.



The correct circuit has been already shown above.

 

[kookooli]

@Easyrider

No, I was not kidding. You are right. It works. I had made a mistake. I had connected opto cathode to Rx line instead of Tx line.

But what is the use of using opto on UART ?

it finally worked ... thank you milan.rajik.
you really helped me. thank you.
Good luck.

 

[abdi110]

See datasheet of opto. If Opto input diode needs 1.6V and 30mA then (5V - 1.6V) / 30 mA = 113E. Power dessipated in resistor = P = VI = IIR = (5 - 1.6) * 30 mA = 102 mW. You can use 1/4W.

I think he asked about R1 and R3.

 

[milan.rajik]

Where is R1 and R3 ? Which image ?

 

[abdi110]

Where is R1 and R3 ? Which image ?

this one

 

[milan.rajik]

It's R2 and R3. To calculate resistor value for R3 it is like this. Lets say CE voltage is 0.4V and VDD is 3.3V and required current through opto output circuit is 5 mA then (3.3V - 0.4V) / 5 mA = R3.

 

[abdi110]

what is the resistor connected to pin number 5 of opto and pin number 1 of micro ?

yes but his question is about R1 and R3