I2C Reset

Douglas Kennedy · Joined: 07 Sep 2003 Posts: 755 Location: Florida

We know that I2C doesn't have a reset. The issue is when using the hardware I2C with other hardware interrupts the I2C bus can get hung on rare occasions. When this happens the PIC watchdog resets the PIC but the external I2C ( Ex. DS1307) is a slave and expects the PIC to complete the transfer it started that the watchdog shut down before the I2C byte was fully transferred.
The following procedure is suggested and I'm hoping someone has tried it.

The procedure is as follows:
1) Master tries to assert a Logic 1 on the SDA line
2) Master still sees a Logic 0 and then generates a clock
pulse on SCL (1-0-1 transition)
3) Master examines SDA. If SDA = 0, go to Step 2; if
SDA = 1, go to Step 4
4) Generate a STOP condition

FvM · Joined: 27 Aug 2008 Posts: 2337 Location: Germany

See Philips/NXP AN10216 Slide 42 http://www.nxp.com/documents/application_note/AN10216.pdf

Ttelmah · Joined: 11 Mar 2010 Posts: 19499

and, yes, it does work.

Have done it on a long I2C bus (using 8296 drivers), where occasionally the hardware would get hung.

Best Wishes