I2C-Bus Opto-Isolation

[NavMicroSystems]

If you ever need to optically isolate the I2C bus:

attached is a working schematic.

It works at up to 400 kHz

[CocaColaKid]

Attachment doesn't work.

[Luciano]

If the GIF file does not open, right-click on it and save it.
To open the GIF file use the tool Imaging for Windows which is
part of Windows 2000 or another similar tool.

Windows 2000:
Start-Programs-Accessories-Imaging


Luciano

[Stump]

If the INT PIC will always act as the master, then only 3 optos are required.
The opto connected to pin 6 of P82B96 can be left out, and pin 6
is then connected to 5v. The clock signal does not need to be bidirectional
unless the EXT units must act as master.

[BigWumpus]

I think, the SCL-signal is also bidirectional, because the slave-device holds down the SCL-signal in order to strecht the read-command until it is freed by the interruptprocess after filling the SSPBUF.

[Stump]

If you use slave devices that do NOT support clock pulse stretching
then you can eliminate one of the optos
see Philips appnote AN255_2
pg 45
www.semiconductors.philips.com/acrobat_download/applicationnotes/AN255_2.pdf

It appears that clock stretching in pbp can be implimented with a define
statement "DEFINE I2C_HOLD 1"