Hi Linus, 2016-12-30 10:07 GMT+01:00 Linus Walleij <[email protected]>: > On Fri, Dec 23, 2016 at 2:09 PM, M'boumba Cedric Madianga > <[email protected]> wrote: >> 2016-12-22 20:11 GMT+01:00 Uwe Kleine-König <[email protected]>: >>> On Thu, Dec 22, 2016 at 02:35:02PM +0100, M'boumba Cedric Madianga wrote: >>>> @@ -337,6 +350,16 @@ >>>> slew-rate = <2>; >>>> }; >>>> }; >>>> + >>>> + i2c1_pins_b: i2c1@0 { >>>> + pins1 { >>>> + pinmux = >>>> <STM32F429_PB9_FUNC_I2C1_SDA>; >>>> + drive-open-drain; >>>> + }; >>>> + pins2 { >>>> + pinmux = >>>> <STM32F429_PB6_FUNC_I2C1_SCL>; >>>> + }; >>> >>> the second doesn't need the open-drain property? Why? >> >> I thought that open-drain was only needed for SDA line. >> But after double-checking I2C specification, it seems that SDA and SCL >> lines need open-drain or open-collector to perform the wired-AND >> function. > > I think I2C SDA/SCL must be open drain by definition. > > It also requires pull-up resistors, I guess you have these mounted on the > board > so you do not need pull-up from the pin controller? Yes, I have 1 pull-up resistor of 1,5K ohm for each line (SDA & SCL) on the board
> > Yours, > Linus Walleij
