Hi Iztok,
On Tue, Nov 8, 2016 at 3:10 PM, <iztok.je...@redpitaya.com> wrote: > Hi Shubhrajyoti, > > By lockup state, I mean an undefined/unhandled state of the HW logic state > machine, > or something similar in the software driver. > Based on symptoms I assume it is a HW lockup. > In practice asking the driver for a new I2C transfer would result in > nothing happening on the I2C bus (signals remain in hi-Z state). > Driver or userspace tool reports a transfer error, but I did not copy it. > And I did not check the state of the driver. > > To enter this mode it was enough to connect an oscilloscope probe to the SDA > signal. > The capacitance of the probe causes a deep voltage fall, which is quickly > corrected by the pullup. > I did not time the glitch, and the shape was partially defined by an I2C > level shifter. > The issue can be repeated with about 80% probability. > > There are two ways to get back to a working state: > 1. create a longer zero pulse (about 50ms manual grounding) on SDA > 2. reset the HW, this was done with a patched driver. Thanks for the explaination. May be recovery mechanism implementation could be considered. > > Regards, > Iztok Jeras > >
