Changes
/* Watchdog */
== Watchdog ==
* [http://fit-pc'''NOTE!''' Not supported in mainline Linux kernel yet.com/wiki/index.php/[[Fitlet:_Linux:_Kernel Custom kernel:_3.16 | Linux Kernel 3.16 for Fitlet]] should be installed to make this feature work* The AMD FCH (Fusion Controller Hub) supports a user configurable watchdog
* Once the watchdog is enabled the system restarts once the timeout period elapses, in order to prevent it the user needs to either feed the watchdog or to disable it
$ sudo apt-get install watchdog
$ echo c > /proc/sysrq-trigger
* As a result, the watchdog is not fed and the system will reboot after 60 sec
== GPIO ==
* '''NOTE!''' Not supported in mainline Linux kernel. [[Fitlet:_Linux:_Kernel:_3.16 | Linux Kernel 3.16 for Fitlet]] should be installed to make this feature work
* GPIO interface on fitlet consists of 9 GPIOs provided by AMD FCH (Fusion Controller Hub)
* The responsible kernel module is gpio_fch
* The kernel module uses the following pin naming convention:
{| cellpadding="3" border="1" style="border: 1px solid rgb(85, 85, 85); border-collapse: collapse;"
|+ GPIO connector pinout
|-
| Pin Number
| Color Code
| GPIO name
| Power domain
| HW source
| Notes
|-
| 1
| Brown
| GPIO89
| 3.3V
| SoC
|
|-
| 2
| Red
| GPIO132
| 3.3V
| SoC
|
|-
| 3
| Orange
| GPIO65
| 3.3V
| SoC
|
|-
| 4
| Yellow
| GPIO66
| 3.3V
| SoC
|
|-
| 5
| Green
| GPIO29
| 1.5V
| Soc
|
|-
| 6
| Blue
| I2C Clock
| 3.3V
| SoC
|
|-
| 7
| Purple
| I2C Data
| 3.3V
| SoC
|
|-
| 8
| Grey
| GPIO73
| 3.3V
| SoC
|
|-
| 9
| White
| GPIO27
| 1.5V
| SoC
|
|-
| 10
| Black
| GPIO28
| 1.5V
| SoC
|
|-
| 11
| Brown
| GPIO12
| 3.3V
| SoC
|
|-
| 12
| Red
| UART Rx
| 3.3V
| SuperIO
|
|-
| 13
| Orange
| UART Tx
| 3.3V
| SuperIO
|
|-
| 14
| Yellow
|
|
| GND
|
|}
* The GPIO sysfs interface allows users to manipulate any GPIO from userspace dynamically.
* A basic example of GPIO P-1 (Brown) usage (as root user):
$ modprobe fch_gpio
$ echo 89 > /sys/class/gpio/export
$ echo out > /sys/class/gpio/gpio89/direction
$ echo 1 > /sys/class/gpio/gpio89/value
## at this point voltage measuring on P-1 (Brown) should give 3.3V
$ echo 0 > /sys/class/gpio/gpio89/value
## at this point voltage measuring on P-1 (Brown) should give 0.0V
$ echo 89 > /sys/class/gpio/unexport
* The GPIO framework and GPIO sysfs interface are documented in https://www.kernel.org/doc/Documentation/gpio/gpio.txt
[[category:fitlet]]
