Hi, On Wed, Jun 17, 2015 at 01:09:53PM +0200, Michael Lawnick wrote: > Am 16.06.2015 um 21:17 schrieb Felipe Balbi: > >With this patch we try to be as close to 50% > >duty cycle as possible. The reason for this > >is that some devices present an erratic behavior > >with certain duty cycles. > > > >One such example is TPS65218 PMIC which fails > >to change voltages when running @ 400kHz and > >duty cycle is lower than 34%. > > > >The idea of the patch is simple: > > > >calculate desired scl_period from requested scl > >and use 50% for tLow and 50% for tHigh. > ... > Hmm, and what's about Philips I2C specification 2.1, Jan 2000, Table 5? > > >PARAMETER SYMBOL STANDARD-MODE FAST-MODE UNIT > > MIN. MAX. MIN. MAX. > >LOW period of the SCL clock tLOW 4.7 – 1.3 – µs > >HIGH period of the SCL clock tHIGH 4.0 – 0.6 – µs > > Your signal is in spec (0.85 µs high, 1,65 low). > Maybe your TPS65218 is just buggy or signals are bad? yes, tps is buggy, it's written in the commit log itself. -- balbi
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