Controlling GPIOs and LEDs

This example demonstrates how to use GPIOs with Gecko OS in general, and how to use GPIOs to control LEDs on Silicon Labs evaluation boards. For details of using GPIOs and peripherals, see Peripherals .

In Gecko OS, a GPIO may have two functions: a standard IO function or an alternative function such as a system indicator, status GPIO or control GPIO. See GPIO Configuration .

When a GPIO is configured with an alternative function, the standard IO function is NOT available and the gpio_dir , gpio_set , and gpio_get commands are disabled for that GPIO.

Before a GPIO can be used to control an LED, it is necessary to first check whether the GPIO is being used for an alternative function. If a GPIO is not being used for an alternative function, but is already in use as a standard GPIO (for another purpose), the GPIO must first be freed up by setting the direction of the GPIO to none using the gpio_dir command.

GPIO Usage

The gpio.usage variable makes it easy to get a list of GPIOs that are already in use.

> get gpio.usage
! #   Description
#10 - Standard I/O
#11 - Standard I/O
#13 - UART1 RX
#14 - UART1 TX
#17 - SPI CLK
#18 - SPI MOSI
#19 - SPI MISO
#21 - system.indicator.network
#22 - system.indicator.wlan

LED Control

The following example shows a board which has two LEDs connected to GPIO 21 & 22.

These LEDs are factory configured as system indicators to dynamically indicate the state of the Wi-Fi and network connection (as shown in the table above). To repurpose the GPIOs as standard IOs for use with LEDs, try the Gecko OS command sequence shown in the table below.

Note! Don't forget to adjust the GPIO numbers to suit your specific board!

set system.indicator.gpio wlan    -1
set system.indicator.gpio network -1
save
reboot

set gpio.alias 21 LED1
set gpio.alias 22 LED2

gpio_dir LED1 out
gpio_dir LED2 out

gpio_set LED1 1
gpio_set LED2 1

gpio_set LED1 0
gpio_set LED2 0

<- Disable the wlan system indicator
<- Disable the network system indicator
<- Save & reboot since system indicator
   functions are setup after a reset

<- Setup a friendly alias for the LED on GPIO 21
<- Setup a friendly alias for the LED on GPIO 22

<- Set the GPIO direction to output
<- Set the GPIO direction to output

<- Turn on LED 1
<- Turn on LED 2

<- Turn off LED 1
<- Turn off LED 2

To re-instate the system indicators, either factory reset the module, or use the following commands.

gpio_dir LED1 none
gpio_dir LED2 none

set system.indicator.gpio wlan    LED1
set system.indicator.gpio network LED2
save
reboot

<- Free up the GPIO aliased to LED1
<- Free up the GPIO aliased to LED2

<- Set the wlan system indicator GPIO to LED1
<- Set the wlan system indicator GPIO to LED2
<- Save & reboot since system indicator
   functions are setup after a reset

GPIO Initialization

GPIOs may be individually configured for initialization after reset using the gpio.init variable. Don't forget to save & reboot to make sure recent GPIO initialization changes take effect.

Supporting Gecko OS Versions

• Gecko OS 4

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