Linux/AM3352: AM3352 i2c-gpio open-drain is invalid.

Paul.Wu

Part Number: AM3352

Tool/software: Linux

Hi,

I used i2c-gpio driver, But the sda can not read ack correctlly from the eeprom. The waveform of the ack is half-high. I think the sda is not input mode, when the ack arrives.

So I think the gpio open-drain mode is invalid. Please help me.

The dts follow.

gpioi2c3: i2c-3 {
#address-cells = <1>;
#size-cells = <0>;
pinctrl-names = "default";
pinctrl-0 = <&i2c3_gpio>;
compatible = "i2c-gpio";
status = "okay";
gpios = <&gpio1 13 GPIO_ACTIVE_HIGH &gpio1 12 GPIO_ACTIVE_HIGH>;
i2c-gpio,sda-open-drain;
i2c-gpio,scl-open-drain;
i2c-gpio,delay-us = <5>;
};

over 6 years ago

0 Paul.Wu over 6 years ago

Intellectual 360 points

i2c3_gpio: i2c3_gpio {
pinctrl-single,pins = <
AM33XX_IOPAD(0x830, PIN_OUTPUT_PULLDOWN | MUX_MODE7) /* (T12) gpmc_ad12.gpio1[12] */
AM33XX_IOPAD(0x834, PIN_OUTPUT_PULLDOWN | MUX_MODE7) /* (R12) gpmc_ad13.gpio1[13] */
>;
};

0 Biser Gatchev-XID over 6 years ago in reply to Paul.Wu

TI__Guru**** 393215 points

Hi,

AM335x I/O pins are not open drain. You will need external pullups on your I2C lines.

0 Paul.Wu over 6 years ago in reply to Biser Gatchev-XID

Intellectual 360 points

Hi ,
I have resolved this issue.

The dts file:
gpioi2c3: i2c-3 {
#address-cells = <1>;
#size-cells = <0>;
pinctrl-names = "default";
pinctrl-0 = <&i2c3_gpio>;

compatible = "i2c-gpio";
gpios = <&gpio1 13 GPIO_ACTIVE_HIGH /* sda */
&gpio1 12 GPIO_ACTIVE_HIGH /* scl */
>;
i2c-gpio,scl-output-only;
i2c-gpio,delay-us = <2>; /* ~100 kHz */
status = "okay";
};

i2c3_gpio: i2c3_gpio {
pinctrl-single,pins = <
AM33XX_IOPAD(0x830, PIN_OUTPUT_PULLUP|MUX_MODE7) /* (T12) gpmc_ad12.gpio1[12] */
AM33XX_IOPAD(0x834, PIN_INPUT_PULLUP|MUX_MODE7) /* (R12) gpmc_ad13.gpio1[13] */
>;
};
The sda must be PIN_INPUT_PULLUP and external pullups .
The scl must be PIN_OUTPUT_PULLUP and external pullups .

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Linux/AM3352: AM3352 i2c-gpio open-drain is invalid.