1. Make sure that the kernel you use supports the necessary driver.
<br>Check the following entries in the kernel config:
<pre> CONFIG_GPIO_PCA953X=[y] CONFIG_I2C=y CONFIG_I2C_CHARDEV=y</pre>
2. Make sure that the appropriate I2C bus is enabled in BIOS settings: <br>
Chipset -> South Cluster Configuration -> LPSS Configuration LPSS I2C #[1-8] Support is set to ACPI mode or PCI mode Set LPSS I2C #[1-8] Speed is set to Standard Mode of Fast Mode
<br>'''NOTE:''' It’s strongly recommended that All all buses are enabled in the range of 1-7
3.Find the GPIO extender on an I2C bus:
<pre>readonly dev_func='17.2' busnum=$(ls -l /sys/bus/i2c/devices/ | sed -ne "/${dev_func}\/i2c_designware/ s/^.*i2c-\([[:digit:]]\{1,2\}\)$/\1/p") busaddr=$(i2cdetect -y -r $busnum | sed -ne 's/^.*\(\(27\|4e\)\).*$/0x\1/Ip') busaddr=$((busaddr)) printf "Device found @ 0x%x on bus %i\n" $busaddr $busnum </pre>
'''Note:''' PCA9335 chip should be found at address 0x27, whereas XRA1201 chip at 0x4e
4. Bind the above found device to driver (superuser privileges are necessary)
<pre>
echo pca9535 $busaddr >/sys/bus/i2c/devices/i2c-${busnum}/new_device
</pre>
Then check the kernel debug messages for a line like the following:
<pre>
i2c i2c-7: new_device: Instantiated device pca9535 at 0x27
</pre>
5. To find the appropriate GPIO, issue the command:
<pre>
ls /sys/bus/i2c/drivers/pca953x/
</pre>
Then look the output for a line like:
<pre>
7-0027
</pre>
And then issue the command:
<pre>
ls /sys/class/gpio/gpiochip*/device -l
</pre>
Afterwards, look at the output for a line like the following:
<pre>
/sys/class/gpio/gpiochip251/device -> ../../../7-0027
</pre>
4. Bind the above found device The bus number and address has to driver be the same in both cases (superuser privileges are necessary7 and 27 in the example). echo pca9535 $busaddr >/sys/bus/i2c/devices/i2c-${busnum}/new_device and check Hence, the kernel debug messages for a gpiochip251 is to be sought; the individual GPIO line like that: i2c i2c-7: new_device: Instantiated device pca9535 at 0x27number are from 251 to 251+15
56. To find the appropriate GPIO issue the command: ls /sys/bus/i2c/drivers/pca953x/and look the output for a line like this: 7-0027and then issue the command: ls /sys/class/gpio/gpiochip*/device -land look the output for a line like this: /sys/class/gpio/gpiochip251/device -> ../../../7-0027 The bus number and address have to be the same in the both cases (7 and 27 in the example). Hence, the gpiochip251 is the sought; the individual GPIO line number are from 251 to 251+15 6. The found GPIO may be operated over sysfs interface in the following way:
issue the commands:
<pre>export n=251 # desired GPIO number echo $n >/sys/class/gpio/export echo out >/sys/class/gpio/gpio$n/direction # desired direction in/out cat /sys/class/gpio/gpio$n/value # read the input value echo 1 > /sys/class/gpio/gpio$n/value # write a value for output </pre>
[[category: fitlet2]]
