Difference between revisions of "GPIO LEDS"
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− | It is possible to switch | + | It is possible to switch LED state using the [[APF28Dev]]/[[OPOS6ULDev]] User button. This button is seen as gpio17 (as seen under APF28Dev [[datasheet]]) under Linux; gpio43 on [[OPOS6ULDev]]. |
+ | Configure the LED trigger as gpio : | ||
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− | Then the trigger gpio can be configured with ''gpio'' file : | + | Then the trigger gpio can be configured with ''gpio'' file (replace 17 with 43 on [[OPOS6ULDev]]) : |
<pre class="apf"> | <pre class="apf"> |
Latest revision as of 17:16, 7 September 2017
How to use gpio-leds driver to manage states of the LEDs connected to your Armadeus Dev board.
Contents
Introduction
You can manage a LED connected to a GPIO pin with a sysfs interface very similar to the standard GPIO sysfs driver, but you will have some new features like triggers (e.g. "heartbeat" trigger will make LED blink like a heart at the rate of the CPU load) . Here are the GPIO used for the user LED on each APF board:
- APF9328: PORT A / bit 2
- APF27: GPIO_PORTF | 14
- APF28: PINID_GPMI_RDY1 (Bank 0 - pin 21)
- APF51: GPIO_PORTA | 2
- APF6: GPIO7 | 12
- OPOS6UL: GPIO3 | 4
Configuration
Note: Following configuration instructions are now done by default in BSP > 5.3, so you can skip them if you use a recent armadeus software |
You need to enable the leds-gpio driver in your kernel and some triggers like the "heartbeat".
- Configure Linux kernel:
$ make linux-menuconfig
Device Drivers ---> --- LED support [*] LED Class Support *** LED drivers *** <*> LED Support for GPIO connected LEDs [*] Platform device bindings for GPIO LEDs *** LED Triggers *** [*] LED Trigger support <*> LED Timer Trigger <*> LED Heartbeat Trigger <*> LED backlight Trigger <*> LED Default ON Trigger
Then, in your apfXX-dev.c, you would need to define your LED before the variable platform_devices[]. This code is already implemented for the APF27, APF28 and APF51 so the source code hereafter (for the APF27) is only present as a reference sample to understand how to activate a GPIO LED driver.
#include <linux/leds.h>
/* GPIO LED */
#if defined(CONFIG_LEDS_GPIO) || defined(CONFIG_LEDS_GPIO_MODULE)
static struct gpio_led apf27dev_led[] = {
{
.name = "apfdev:green:user",
.default_trigger = "heartbeat",
.gpio = (GPIO_PORTF | 14),
.active_low = 1,
},
};
static struct gpio_led_platform_data apf27dev_led_data = {
.num_leds = ARRAY_SIZE(apf27dev_led),
.leds = apf27dev_led
};
static struct platform_device apf27dev_led_dev = {
.name = "leds-gpio",
.id = -1,
.dev = {
.platform_data = &apf27dev_led_data,
},
};
#endif /* CONFIG_LEDS_GPIO */
Add the LED to get it managed by the kernel.
static struct platform_device *platform_devices[] __initdata = {
#if defined(CONFIG_LEDS_GPIO) || defined(CONFIG_LEDS_GPIO_MODULE)
&apf27dev_led_dev,
#endif
ALSA_SOUND
};
Then rebuild and update your bard with the new kernel. Upon the next kernel boot you should see the LED flash like a heartbeat (if you have activated the "heartbeat" trigger)
Usage
- In following instructions replace $LED with "apfdev\:green\:user", except on OPOS6ULDev where you will use "User":
# ls /sys/class/leds/$LED/ brightness max_brightness subsystem uevent device power trigger
You can change the trigger behaviors. By default, Heartbeat is selected:
- "heatbeat": led blinks like a heart and blink frequency will change according o the CPU activity.
- "nand-disk": the led will blink each time nand access occur (try with sync command to see it blinking).
# cat /sys/class/leds/$LED/trigger none nand-disk mmc0 timer [heartbeat] backlight gpio default-on # echo none > /sys/class/leds/$LED/trigger
Switch on and off the LED
# cat /sys/class/leds/$LED/max_brightness > /sys/class/leds/$LED/brightness # echo 0 > /sys/class/leds/$LED/brightness
It is possible to switch LED state using the APF28Dev/OPOS6ULDev User button. This button is seen as gpio17 (as seen under APF28Dev datasheet) under Linux; gpio43 on OPOS6ULDev. Configure the LED trigger as gpio :
# echo "gpio" > /sys/class/leds/$LED/trigger
New config files are available :
# ls /sys/class/leds/$LED/ brightness gpio power uevent desired_brightness inverted subsystem device max_brightness trigger
Then the trigger gpio can be configured with gpio file (replace 17 with 43 on OPOS6ULDev) :
# echo 17 > /sys/class/leds/$LED/gpio
Then pushing the user switch will now commute the LED state.