GPIO monitoring

VIM4 Android
1

Hi All,

I was wondering if its possible to monitor GPIO for a high/low signal?

How would you access the GPIO from an adroid app?

I do not have a ton of experience so adding a little extra detail might save me.

Thanks!
Aaron

2

@chandrian
title: Access GPIO Usage

This guide is about how to access the GPIO using Android.

{% note warn Note %}
All operations on GPIO are performed under root privileges, switch to root:

$ su
#

{% endnote %}

Get GPIO value

Calculation method

The calculation method of the GPIO array is: Number = Banks + Pins.

  1. Banks refers to the base value of GPIO Ranges.
  2. Pins refers to the sorting of the GPIO pins you need to calculate in the corresponding ranges.

Numerical calculation example

Amlogic chips usually include two GPIO Ranges, AOBUS and Periphs. There is a calculation example for each Ranges here for reference.

  1. Get Banks:
# cat /sys/kernel/debug/pinctrl/fe000000.apb4\:pinctrl\@4000-pinctrl-meson/gpio-ranges
GPIO ranges handled:
0: periphs-banks GPIOS [355 - 511] PINS [0 - 156]
  1. Get Pins:
# cat /sys/kernel/debug/pinctrl/fe000000.apb4\:pinctrl\@4000-pinctrl-meson/pins
registered pins: 157
pin 0 (GPIOB_0)  fe000000.apb4:pinctrl@4000
pin 1 (GPIOB_1)  fe000000.apb4:pinctrl@4000
pin 2 (GPIOB_2)  fe000000.apb4:pinctrl@4000
pin 3 (GPIOB_3)  fe000000.apb4:pinctrl@4000
pin 4 (GPIOB_4)  fe000000.apb4:pinctrl@4000
pin 5 (GPIOB_5)  fe000000.apb4:pinctrl@4000
pin 6 (GPIOB_6)  fe000000.apb4:pinctrl@4000
pin 7 (GPIOB_7)  fe000000.apb4:pinctrl@4000
pin 8 (GPIOB_8)  fe000000.apb4:pinctrl@4000
pin 9 (GPIOB_9)  fe000000.apb4:pinctrl@4000
...
pin 109 (GPIOT_18)  fe000000.apb4:pinctrl@4000
pin 110 (GPIOT_19)  fe000000.apb4:pinctrl@4000
...
  1. Calculate Number:

Take GPIOT_18 and GPIOT_19 as an examples here.

GPIOT_18 = Banks + Pins = 355 + 109 = 464
GPIOT_19 = Banks + Pins = 355 + 110 = 465

GPIO usage examples

  • Request the gpio(GPIOT_19)
# echo 465  > /sys/class/gpio/export
  • Config the gpio(GPIOT_19) as output
# echo out > /sys/class/gpio/gpio465/direction
  • Config the gpio(GPIOT_19) as high level output
# echo 1 >  /sys/class/gpio/gpio465/value
  • Config the gpio(GPIOT_19) as low level output
# echo 0 >  /sys/class/gpio/gpio465/value
  • Config the gpio(GPIOT_19) as input
# echo in > /sys/class/gpio/gpio465/direction
  • Get the gpio(GPIOT_19) level
# cat /sys/class/gpio/gpio465/value
  • Release the gpio(GPIOT_19)
# echo 465 > /sys/class/gpio/unexport

Third-Party Applications examples

  • Get root permision
Process mProcess = Runtime.getRuntime().exec("su");
  • Request the gpio(GPIOT_19)
DataOutputStream os = new DataOutputStream(mProcess.getOutputStream());
os.writeBytes("echo " + 465 + " > /sys/class/gpio/export\n");
  • Config the gpio(GPIOT_19) as high level output
os.writeBytes("echo out > /sys/class/gpio/gpio" + 465 + "/direction\n");
os.writeBytes("echo 1 > /sys/class/gpio/gpio" + 465 + "/value\n");
  • Config the gpio(GPIOT_19) as input
os.writeBytes("echo in > /sys/class/gpio/gpio" + 465 + "/direction\n");
  • Get the gpio(GPIOT_19) level
Runtime runtime = Runtime.getRuntime(); 
Process process = runtime.exec("cat " + "/sys/class/gpio/gpio" + 465 + "/value");  
InputStream is = process.getInputStream(); 
InputStreamReader isr = new InputStreamReader(is); 
BufferedReader br = new BufferedReader(isr); 
String line ; 
while (null != (line = br.readLine())) { 
 return Integer.parseInt(line.trim()); 
}
  • Release the gpio(GPIOT_19)
 os.writeBytes("echo " + 465 + " > /sys/class/gpio/unexport\n");