Isolated UART communication

Hi All,

Any suggestions about making high-speed (16k baud) opto-isolated UART communications between

1. Microcoltroller to Microcontroller at TTL Levels.
2. RS232 port and microcontroller

How do you guys do it. I use two opto couplers (4n35) for receive and transmit side but it has its speed limitations.

Thanks, Rohan

Go to Analog Devices Web pages , and click 'isolators'.

Hi, Thanks. I forgot to add that I need a cheap working solution for mass production. Something with normal optocouplers. is it possible. Thanks, Rohan

What is high speed ? 110/9600/115k2/12Mbit/s ? What isolation requirements 0.5 kV, 2.5 kV, 110 kV or 400 kV ?

Standard 20 mA current loop or +/-10 mA bipolar current loop.

At least RS-232C did not specify speeds above 9k6, so going to 20 mA current loop would be sufficient.

Paul

Then use a faster opto-coupler. I have had good results with the SFH6138. These are couplers with a darlington stage when you can pull the base of the second transistor to ground with for instance a 4k7 ohm resistor. This gives you a massive increase in speed. I have run this at 115200 baud without a glitch.

Meindert

You still have not said how fast you need to go!

We use H11L1 optos (Schmitt, ~1us, 1.6mA ), as a good trade off between speed and price.

-jg

Regards Anton Erasmus

In his first line:

Meindert

I don't know where you got the parenthesised portion of the text from but it was not in the original post of this thread nor any subsequent one from the OP.

Original message was:-

... snip ...

Second post in the thread, which included:

It was posted 2 min after the first post.

My newsreader had organised that into a different thread so it was unseen when I queried the parenthesis portion. Sorry.

Nope, Not on what I was reading; but no matter, the advice I gave was still sound.

-jg

MIDI runs at 31.25Kb...most schematics I've seen for a midi interface use a 6N138. I've built several interfaces with them and had no problems. It's been about 5 years since I built a midi interface, but I presume they're still available and inexpensive. HTH, Bill

Tauno Voipio ha scritto:

I suggest ADUM1201

-- Per rispondermi sostituisci l'asterisco con la chiocciola e il punto