Changes

* This application note applies to fitlet2 supports I2C GPIO extender if configured with the [http://fit-pc.com/wiki/index.php/Fitlet2_FACET_Cards#FC-SCG FC-SCG FACET]FACET-Card running Linux.* It provides an example of how to use the supported I2C GPIO extender feature of FC-SCG under Linux.

==I2c gpio I2C GPIO extender binding and usage==

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=yCONFIG_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 buses are enabled in the range of 1-7

CONFIG_GPIO_PCA953X=[y] CONFIG_I2C=y CONFIG_I2C_CHARDEV=y Make sure that 3.Find the appropriate GPIO extender on an I2C bus is enabled in BIOS settings:Chipset -<pre> South Cluster Configuration -> LPSS ConfigurationLPSS I2C #[1-8] Support is set to ACPI mode or PCI modereadonly dev_func='17.2' Set LPSS I2C #[1busnum=$(ls -8] Speed is set to Standard Mode of Fast Mode NB: All buses must be enabled in the range 1-7, not only I2Cl /sys/bus/i2c/devices/ | sed -7ne   Determine the type of the GPIO extender chip"/${dev_func}\/i2c_designware/ s/^. Possible options are*i2c-\([[:  PCA9335XRA1201For this purpose i2cdetect utility may be useddigit:]]\{1,2\}\)$/\1/p")   busaddr=$(i2cdetect -y -r 7$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  Issue the following command (superuser privileges are necessary) echo pca9535 0x27> /sys/bus/i2c/devices/i2c-7/new_device in case pca9535 chip found or echo pca9535 0x4e> /sys/bus/i2c/devices/i2c-7/new_device and check the kernel debug messages for a line like that:

</pre> 5. To find the appropriate GPIO , issue the command:<pre>

</pre>and Then look the output for a line like this:<pre>

</pre>and And then issue the command:<pre>

</pre>and Afterwards, look at the output for a line like thisthe following:<pre>

The bus number and address have has to be the same in the both cases (7 and 27 in the example).Hence, the gpiochip251 is the to be sought; the individual GPIO line number are from 251 to 251+15

 6. The found GPIO found may be operated over sysfs interface this in the following way: