From: "M'boumba Cedric Madianga" <cedric.madianga@gmail.com>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Wolfram Sang" <wsa@the-dreams.de>,
"Rob Herring" <robh+dt@kernel.org>,
"Maxime Coquelin" <mcoquelin.stm32@gmail.com>,
"Alexandre Torgue" <alexandre.torgue@st.com>,
"Patrice Chotard" <patrice.chotard@st.com>,
"Russell King" <linux@armlinux.org.uk>,
"linux-i2c@vger.kernel.org" <linux-i2c@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v7 3/5] ARM: dts: stm32: Add I2C1 support for STM32F429 SoC
Date: Fri, 30 Dec 2016 15:36:53 +0100 [thread overview]
Message-ID: <CAOAejn2dWj7m2PpbupiUHQMEceUNcLOHE58iLRKutq3i47pdWA@mail.gmail.com> (raw)
In-Reply-To: <CACRpkdaNyL2iV+risLudW=O55w81-AuEZhMwRu9NLdXpnC2r1w@mail.gmail.com>
Hi Linus,
2016-12-30 10:07 GMT+01:00 Linus Walleij <linus.walleij@linaro.org>:
> On Fri, Dec 23, 2016 at 2:09 PM, M'boumba Cedric Madianga
> <cedric.madianga@gmail.com> wrote:
>> 2016-12-22 20:11 GMT+01:00 Uwe Kleine-König <u.kleine-koenig@pengutronix.de>:
>>> 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
next prev parent reply other threads:[~2016-12-30 14:37 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-22 13:34 [PATCH v7 0/5] Add support for the STM32F4 I2C M'boumba Cedric Madianga
2016-12-22 13:35 ` [PATCH v7 1/5] dt-bindings: Document the STM32 I2C bindings M'boumba Cedric Madianga
2016-12-22 13:35 ` [PATCH v7 2/5] i2c: Add STM32F4 I2C driver M'boumba Cedric Madianga
2016-12-23 9:00 ` Uwe Kleine-König
2016-12-23 12:41 ` M'boumba Cedric Madianga
2016-12-28 21:21 ` Uwe Kleine-König
2016-12-28 22:20 ` M'boumba Cedric Madianga
2017-01-02 13:31 ` M'boumba Cedric Madianga
2016-12-22 13:35 ` [PATCH v7 3/5] ARM: dts: stm32: Add I2C1 support for STM32F429 SoC M'boumba Cedric Madianga
2016-12-22 19:11 ` Uwe Kleine-König
2016-12-23 13:09 ` M'boumba Cedric Madianga
2016-12-30 9:07 ` Linus Walleij
2016-12-30 14:36 ` M'boumba Cedric Madianga [this message]
2016-12-22 13:35 ` [PATCH v7 4/5] ARM: dts: stm32: Add I2C1 support for STM32429 eval board M'boumba Cedric Madianga
2016-12-22 13:35 ` [PATCH v7 5/5] ARM: configs: stm32: Add I2C support for STM32 defconfig M'boumba Cedric Madianga
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