add i2c expander PCA9535 using device tree

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1

Hello all,

I am trying to add the PCA 9535 expander on the i2c2 bus on P9. 23 and P9.24 using the device tree but I cannot detect it when booting the board with the kernel 4.1.15.
below the way I declare the device on the DTS.

Do you know what I am doing wrong?

&omap3_pmx_core {
pinctrl-names = “default”;
pinctrl-0 = <
&hsusb2_pins

;
i2c2_pins: pinmux_i2c_pins {
pinctrl-single,pins = <
0x18E (PIN_INPUT_PULLUP | MUX_MODE0) /* i2c2_scl.gpio_168 /
0x190 (PIN_INPUT_PULLUP | MUX_MODE0) / i2c2_sda.gpio_136 */

;
};

&i2c2 {

clock-frequency = <400000>;

pca9535: gpio@20 {
compatible = “nxp, pca9535”;
gpio-controller;
#gpio-cell = <2>;
reg = <0x20>;
status = “okay”;

};

gpio@21 {
compatible = “nxp, pca9535”;
gpio-controller;
#gpio-cell = <2>;
reg = <0x21>;
status = “okay”;

};
gpio@22 {
compatible = “nxp, pca9535”;
gpio-controller;
status = “okay”;
#gpio-cell = <2>;
reg = <0x22>;

};
gpio@24 {
compatible = “nxp, pca9535”;
gpio-controller;
status = “okay”;
#gpio-cell = <2>;
reg = <0x24>;

};
};

&gpio5 {
pinctrl-names = “defaults”;
pinctrl-0 = <
&gpio_pins
&i2c2_pins

;
};

2

You didn’t say which version of OS you were running.
The I2C busses were renumbered in later OS.
Since you mentioned kernel 4.1.15, I will assume that you are running Debian 8

In Debian 8, I2C2 is pinned out to P9-19 and P9-20 by default. (No device tree changes necessary.)
Hook your expander there and see if you can see it with i2cdetect.

— Graham

3

Hello Graham,

Thanks for tour quick reply, I am using Debian 8 Jessie indeed.

I have modified my dts as following and it is working fine expect the expander at adress 0x20 I don’t know why?

&i2c2 {

clock-frequency = <400000>;
status = “okay”;

pca953x_0:gpio@20 {
compatible = “nxp, pca9535”;
reg = <0x20>;
};
pca953x_1:gpio@21 {
compatible = “nxp,pca9535”;
reg = <0x21>;
};

pca953x_2:gpio@22 {
compatible = “nxp,pca9535”;
reg = <0x22>;
};

pca953x_3gpio@24 {
compatible = “nxp,pca9535”;
reg = <0x24>;
};

It looks like the gpio adress from 1024 to gpio1040 are forbidden? see my log below:

GPIOs 976-991, i2c/1-0024, pca9535, can sleep:
gpio-976 (sysfs ) in lo
gpio-977 (sysfs ) in lo
gpio-978 (sysfs ) in lo
gpio-979 (sysfs ) in lo
gpio-980 (sysfs ) in lo
gpio-981 (sysfs ) in lo
gpio-982 (sysfs ) in lo
gpio-983 (sysfs ) in lo
gpio-984 (sysfs ) in lo
gpio-985 (sysfs ) in lo
gpio-986 (sysfs ) in lo
gpio-987 (sysfs ) in lo
gpio-989 (sysfs ) in lo
gpio-990 (sysfs ) in hi
gpio-991 (sysfs ) in lo

GPIOs 992-1007, i2c/1-0022, pca9535, can sleep:
gpio-992 (sysfs ) in lo
gpio-993 (sysfs ) in lo
gpio-994 (sysfs ) in lo
gpio-995 (sysfs ) in lo
gpio-996 (sysfs ) in lo
gpio-997 (sysfs ) in lo
gpio-998 (sysfs ) in lo
gpio-999 (sysfs ) in lo
gpio-1000 (sysfs ) in lo
gpio-1001 (sysfs ) in lo
gpio-1002 (sysfs ) in lo
gpio-1003 (sysfs ) in lo
gpio-1004 (sysfs ) in lo
gpio-1005 (sysfs ) in lo
gpio-1006 (sysfs ) in lo
gpio-1007 (sysfs ) in lo

GPIOs 1008-1023, i2c/1-0021, pca9535, can sleep:
gpio-1008 (sysfs ) in lo
gpio-1009 (sysfs ) in lo
gpio-1010 (sysfs ) in lo
gpio-1011 (sysfs ) in lo
gpio-1012 (sysfs ) in lo
gpio-1013 (sysfs ) in lo
gpio-1014 (sysfs ) in lo
gpio-1015 (sysfs ) in lo
gpio-1016 (sysfs ) in lo
gpio-1017 (sysfs ) in lo
gpio-1018 (sysfs ) in lo
gpio-1019 (sysfs ) in lo
gpio-1020 (sysfs ) in lo
gpio-1021 (sysfs ) in lo
gpio-1022 (sysfs ) in lo
gpio-1023 (sysfs ) out hi

4

my i2cdetect show the following and we can see that expand 20 is still free:

WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-1 using read byte commands.
I will probe address range 0x03-0x77.
Continue? [Y/n] y
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: – -- – -- – -- – -- – -- – -- –
10: – -- – -- – -- – -- – -- – -- – -- – --
20: 20 UU UU – UU – -- – -- – -- – -- – -- –
30: – -- – -- – -- – -- – -- – -- – -- – --
40: – -- – -- – -- – -- – -- – -- – -- – --
50: 50 – -- – -- – -- – -- – -- – -- – -- –
60: – -- – -- – -- – -- – -- – -- – -- – --
70: – -- – -- – -- – --

5

I am not sure why the system is not acquiring address 0x20.

I would try removing the space after the comma, in line 'compatible = “nxp, pca9535”;'
for address 20 so that it is identical to the lines that do working.

— Graham

6

Thank you Graham, indeed that was the issue. kind of stupid mistake! :pensive: