Difference between revisions of "Application note - GPIO on fitlet2 with FC-SCG running Linux"
(Created page with "fitlet2 supports I2C GPIO extender if configured with the [http://fit-pc.com/wiki/index.php/Fitlet2_FACET_Cards#FC-SCG FC-SCG FACET] ==I2c gpio extender binding and usage==...") (change visibility) |
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CONFIG_I2C_CHARDEV=y | CONFIG_I2C_CHARDEV=y | ||
| − | Make sure that the appropriate I2C bus is enabled in BIOS settings: | + | 2. Make sure that the appropriate I2C bus is enabled in BIOS settings: |
Chipset -> South Cluster Configuration -> LPSS Configuration | Chipset -> South Cluster Configuration -> LPSS Configuration | ||
| − | LPSS I2C #[1-8] Support is set to ACPI mode or PCI mode | + | '''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 | + | Set LPSS I2C #[1-8] Speed''' is set to '''Standard Mode''' of '''Fast Mode''' |
| − | + | '''NOTE:''' All buses must be enabled in the range 1-7, not only I2C-7 | |
| − | Determine the type of the GPIO extender chip. Possible options are: | + | 3. Determine the type of the GPIO extender chip. Possible options are: |
| − | PCA9335 | + | * PCA9335 |
| − | XRA1201 | + | * XRA1201 For this purpose i2cdetect utility may be used: |
| − | For this purpose i2cdetect utility may be used: | + | |
| − | + | i2cdetect -y -r 7 | |
| − | i2cdetect -y -r 7 | + | |
PCA9335 chip should be found at address 0x27, whereas XRA1201 chip at 0x4e | PCA9335 chip should be found at address 0x27, whereas XRA1201 chip at 0x4e | ||
| − | Issue the following command (superuser privileges are necessary) | + | 4. Issue the following command (superuser privileges are necessary) |
| − | echo pca9535 0x27> /sys/bus/i2c/devices/i2c-7/new_device | + | echo pca9535 0x27> /sys/bus/i2c/devices/i2c-7/new_device |
in case pca9535 chip found | in case pca9535 chip found | ||
| Line 38: | Line 36: | ||
or | or | ||
| − | echo pca9535 0x4e> /sys/bus/i2c/devices/i2c-7/new_device | + | echo pca9535 0x4e> /sys/bus/i2c/devices/i2c-7/new_device |
and check the kernel debug messages for a line like that: | and check the kernel debug messages for a line like that: | ||
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| − | To find the appropriate GPIO issue the command: | + | 5. To find the appropriate GPIO issue the command: |
| − | ls /sys/bus/i2c/drivers/pca953x/ | + | ls /sys/bus/i2c/drivers/pca953x/ |
and look the output for a line like this: | and look the output for a line like this: | ||
| − | 7-0027 | + | '''7-0027''' |
and then issue the command: | and then issue the command: | ||
| − | ls /sys/class/gpio/gpiochip*/device -l | + | ls /sys/class/gpio/gpiochip*/device -l |
and look the output for a line like this: | and look the output for a line like this: | ||
| − | /sys/class/gpio/gpiochip251/device -> ../../../7-0027 | + | /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). | The bus number and address have to be the same in the both cases (7 and 27 in the example). | ||
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| − | The found GPIO may be operated over sysfs interface this way: | + | 6. The found GPIO may be operated over sysfs interface this way: |
issue the commands: | issue the commands: | ||
| − | export n=251 # desired GPIO number | + | export n=251 # desired GPIO number |
| − | echo $n >/sys/class/gpio/export | + | echo $n >/sys/class/gpio/export |
| − | echo out >/sys/class/gpio/gpio$n/direction # desired direction in/out | + | echo out >/sys/class/gpio/gpio$n/direction # desired direction in/out |
| − | cat /sys/class/gpio/gpio$n/value # read the input value | + | cat /sys/class/gpio/gpio$n/value # read the input value |
| − | echo 1 > /sys/class/gpio/gpio$n/value # write a value for output | + | echo 1 > /sys/class/gpio/gpio$n/value # write a value for output |
Revision as of 08:34, 27 September 2018
fitlet2 supports I2C GPIO extender if configured with the FC-SCG FACET
I2c gpio extender binding and usage
1. Make sure that the kernel you use supports the necessary driver. Check the following entries in the kernel config:
CONFIG_GPIO_PCA953X=[y] CONFIG_I2C=y CONFIG_I2C_CHARDEV=y
2. Make sure that the appropriate I2C bus is enabled in BIOS settings: 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
NOTE: All buses must be enabled in the range 1-7, not only I2C-7
3. Determine the type of the GPIO extender chip. Possible options are:
- PCA9335
- XRA1201 For this purpose i2cdetect utility may be used:
i2cdetect -y -r 7
PCA9335 chip should be found at address 0x27, whereas XRA1201 chip at 0x4e
4. 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:
i2c i2c-7: new_device: Instantiated device pca9535 at 0x27
5. To find the appropriate GPIO issue the command:
ls /sys/bus/i2c/drivers/pca953x/
and look the output for a line like this:
7-0027
and then issue the command:
ls /sys/class/gpio/gpiochip*/device -l
and 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 this way:
issue the commands:
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
