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

"Rohan" <rohanshar@gmail.com> wrote in message
news:1178217776.917873.48760@n76g2000hsh.googlegroups.com...
> 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.

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

On 3 May 2007 11:42:56 -0700, Rohan <rohanshar@gmail.com> wrote:

>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.

http://www.nve.com make TTL compatible isolators that can handle data
rates of >50Mb/s.
Analog devices also has a range of products that uses the same sort of
technology for high speed isolation.
http://www.analog.com/en/subCat/0,2879,767%255F827%255F0%255F%255F0%255F,00.html

Regards
  Anton Erasmus

"Rohan" <rohanshar@gmail.com> wrote in message
news:1178217776.917873.48760@n76g2000hsh.googlegroups.com...
> 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

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