FriendlyThings for Rockchip

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Note: the steps and methods presented here apply to all FriendlyElec's Rockchip based boards. For steps and methods that apply to other platforms refer to FriendlyThings

1 Introduction

FriendlyThings is an Android SDK developed by FriendlyElec to access hardware. Users can use it to access various hardware resources Uart, SPI, I2C, GPIO etc on a FriendlyElec ARM board under Android. This SDK is based on Android-NDK. Users can use it to develop popular IoT applications without directly interacting with drivers.

2 Android Versions

The Android BSPs provided by FriendlyElec already have FriendlyThings SDK(, as shown below:

  • Android 12 (rk3568 & rk3588)

BSP source code download link:
Latest ROM download link:

  • Android 7.1.2-rk3399

BSP source code download link:
BSP source code location on the network disk: sources/rk3399-android-7.git-YYYYMMDD.tgz
Latest ROM download link:

  • Android 8.1-rk3399

BSP source code download link:
BSP source code location on the network disk: sources/rk3399-android-8.1.git-YYYYMMDD.tgz
Latest ROM download link:

3 List of Applicable Boards

FriendlyThings SDK( works with the following FriendlyElec RK3399/RK3568/RK3588 based boards:

  • NanoPC-T6
  • NanoPi-R6S/R6C
  • NanoPi-R5S/R5C
  • NanoPC-T4
  • NanoPi M4 (an external eMMC module is needed)
  • NanoPi NEO4 (an external eMMC module is needed)

FriendlyThings might also work with other FriendlyElec boards such as Samsung S5P4418/S5P6818, Samsung S5PV210, Allwinner H3/H5 etc. For more details refer to FriendlyThings

4 Quick Start

4.1 Step 1: Include in APP

Clone the following library locally:

git clone

Copy all the files under the libs directory to your working directory and create a "com/friendlyarm" directory in your Android project's src directory, copy the whole "java/FriendlyThings" to your newly created "com/friendlyarm" directory. The whole project directory will look like this(Note:AndroidStudio's project may be a little bit different):

├── AndroidManifest.xml
├── libs
│   ├── arm64-v8a
│   │   └──
│   └── armeabi
│       └──
├── src
│   └── com
│       └── friendlyarm
│           ├── FriendlyThings
│           │   ├──
│           │   ├──
│           │   ├──
│           │   ├──
│           │   ├──
│           │   ├──
│           │   └──

Import the following components and the major APIs are included in the file:

import com.friendlyarm.FriendlyThings.HardwareControler;
import com.friendlyarm.FriendlyThings.SPIEnum;
import com.friendlyarm.FriendlyThings.GPIOEnum;
import com.friendlyarm.FriendlyThings.FileCtlEnum;
import com.friendlyarm.FriendlyThings.BoardType;

4.2 Step 2: Give APP System Right

Your app needs the system right to access hardware resources;
Give your app the system right by making changes in the AndroidManifest.xml file and the file;
It is better to include your app in your Android source code and compile them together. If your app is not compiled together with your Android source code you have to go through tedious steps to compile your app and sign your app to give it the system right.

4.2.1 Modify AndroidManifest.xml

Add the following line in the manifest node in the AndroidManifest.xml file:


4.2.2 Modify

Create an file(the simplest way is to copy a sample file), modify the file by adding a line LOCAL_CERTIFICATE := platform :

LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_SRC_FILES := $(call all-subdir-java-files)
LOCAL_CFLAGS := -lfriendlyarm-hardware
include $(BUILD_PACKAGE)

4.3 Final Step: Compile Your APP Together with Android Source Code

Go to Android source code's root directory and run "" to export environmental variables, enter your app's directory and run "mm" to compile:
For example: compile the GPIO_LED_Demo on RK3399:

cd rk3399-android-8.1
cd vendor/friendlyelec/apps/GPIO_LED_Demo

4.4 Sample project in Android Studio

5 APIs in Library

Refer to this wiki site:FriendlyThings APIs

6 Access Hardware on Android

6.1 Serial Port

The kernel has enabled the following serial ports for testing by default (should be based on kernel dts configuration), to use more serial ports you can configure the kernel dts yourself:

CPU Model Port Device Node
RK3588 NanoPC-T6 UART6 /dev/ttyS6
RK3588S NanoPi-R6S/R6C UART5 /dev/ttyS5
RK3568 NanoPi-R5S UART9 /dev/ttyS9
RK3399 NanoPC-T4 UART4 /dev/ttyS4

6.1.1 APIs for Accessing Serial Ports

HardwareControler.openSerialPortEx //opens a serial port.   //polls a serial port's status and checks if it has data to be read or if data can be written to it.     //reads data from a serial port.
HardwareControler.write    //writes data to a serial port.
HardwareControler.close    //closes a serial port.

For more details refer to :FriendlyThings APIs

6.2 GPIO

You can access GPIO by calling sysfs APIs. You need to access the "/sys/class/gpio" directory, write a GPIO index number you want to access to the export file, and set the GPIO's direction and value.

The following lists the pins that the kernel configures as GPIO (should be based on kernel dts configuration): Here is a list of GPIOs FriendlyElec's RK3399 boards support:

6.2.1 NanoPC T6

Physical Index GPIO Index
Pin7 106
Pin12 111
Pin15 39
Pin16 107
Pin18 108
Pin26 40

6.2.2 NanoPi R6C

Physical Index GPIO Index
Pin7 128
Pin11 129
Pin13 130
Pin15 133
Pin16 134
Pin18 137
Pin22 138

6.2.3 NanoPi R6S

Physical Index GPIO Index
Pin3 43
Pin5 41
Pin6 44
Pin7 42
Pin9 47
Pin10 46

6.2.4 NanoPi R5S

Physical Index GPIO Index
Pin3 115
Pin5 114
Pin6 97
Pin7 113
Pin11 116
Pin12 117

6.2.5 NanoPC T4

Physical Index GPIO Index
Pin11 33
Pin12 50
Pin15 36
Pin16 54
Pin18 55
Pin22 56
Pin37 96
Pin38 125
Pin40 126

6.2.6 NanoPi M4/M4v2/M4B/NEO4

Physical Index Linux Index
Pin11 33
Pin12 50
Pin15 36
Pin16 54
Pin18 55
Pin22 56

6.2.7 SOM-RK3399/SOM-RK3399v2

Physical Index GPIO Index
Pin7 41
Pin9 42

6.2.8 APIs for Accessing GPIO

HardwareControler.exportGPIOPin      //exports a GPIO.
HardwareControler.setGPIODirection   //sets a GPIO's direction.
HardwareControler.getGPIODirection   //gets a GPIO's direction.
HardwareControler.setGPIOValue    //sets a GPIO's value.
HardwareControler.getGPIOValue    //gets a GPIO's value
HardwareControler.unexportGPIOPin //unexports a GPIO.

For more details refer to:FriendlyThings APIs

6.2.9 Testing GPIO

You can use a FriendlyElec's LED module to test GPIOs. Set a HIGH to turn on the LED and a LOW to turn off the LED.

6.3 ADC

You can access ADC like accessing files on Android.

6.3.1 RK3588

The file node corresponding to channel2 is shown below, this ADC can be used to query the input voltage of USB-C:

Channel Node
Channel 2 /sys/devices/platform/fec10000.saradc/iio:device0/in_voltage2_raw

6.3.2 RK3568

The file node for channel2 is shown below, this ADC can be used to query the input voltage of USB-C:

Channel Node
Channel 2 /sys/devices/platform/fe720000.saradc/iio:device0/in_voltage2_raw

6.3.3 RK3399

RK3399 populates three ADC channels 0, 2 and 3 and here is a list of the channels and their corresponding nodes:

Channel Node
Channel 0 /sys/devices/platform/ff100000.saradc/iio:device0/in_voltage0_raw
Channel 2 /sys/devices/platform/ff100000.saradc/iio:device0/in_voltage2_raw
Channel 3 /sys/devices/platform/ff100000.saradc/iio:device0/in_voltage3_raw

6.4 PWM

6.4.1 NanoPC-T6

Pin32 is configured as PWM by default

6.4.2 NanoPi-R6C

Pin29 is configured as PWM by default

6.4.3 RK3399

Note: The PWM interface is already used by the fan by default. If you want to control the PWM by yourself, you need to disable the fan first,
Please refer to:
Template:RK3399 Android PWMFan

You can access PWMs by calling sysfs APIs. You can access the nodes under the "/sys/class/pwm/pwmchip1" directory. Here is code sample to control a PWM fan: APIs for Accessing PWM
  • Export PWM0 to users
echo 0 > /sys/class/pwm/pwmchip1/export
  • Control a PWM fan's speed by setting the PWM's period and duty_cycle.
echo 0 > /sys/class/pwm/pwmchip1/pwm0/enable
echo 50000 > /sys/class/pwm/pwmchip1/pwm0/period
echo 1 > /sys/class/pwm/pwmchip1/pwm0/enable
echo 45000 > /sys/class/pwm/pwmchip1/pwm0/duty_cycle Testing PWM

Connect a PWM fan(3 pins) to a NanoPC-T4's fan port to test it.

6.5 I2C

6.5.1 RK3399

To test I2C we connected a FriendlyElec's LCD1602 module to a NanoPC-T4 and ran the I2C demo program:

Physical Index I2C Functions
Pin3 I2C2_SDA(3V)
Pin5 I2C2_SCL(3V)
Pin6 GND

Here is a hardware setting:

6.6 RTC

Note: Scheduled power on/off is only supported on certain models, such as NanoPC-T4.
You can access RTC by calling APIs under the "/sys/class/rtc/rtc0/" directory. For instance you can check the current RTC time by running the following commands:

cat /sys/class/rtc/rtc0/date
# 2018-10-20                                                              
cat /sys/class/rtc/rtc0/time                                            
# 08:20:14

Set power-on time. For instance power on in 120 seconds:

#Power on in 120 seconds
echo +120 >  /sys/class/rtc/rtc0/wakealarm


6.7 Watch dog

It is quite straightforward to access the watch dog. You can simply open the "/dev/watchdog" device and write characters to it.If for any reason no characters can be written to the device the system will reboot in a moment:

mWatchDogFD ="/dev/watchdog", FileCtlEnum.O_WRONLY);
HardwareControler.write(mWatchDogFD, "a".getBytes());


6.8 SPI

6.8.1 RK3399 Enable SPI

The SPI and UART4 share the same pins. You need to modify the kernel's DTS file to enable the SPI by running the following commands:
Edit the DTS file: arch/arm64/boot/dts/rockchip/rk3399-nanopi4-common.dtsi:

vim arch/arm64/boot/dts/rockchip/rk3399-nanopi4-common.dtsi

You need to replace "ANDROID_SOURCE" to your real source. In our system it is either Android7's or Android8's source code directory.

Locate spi1's definition:

&spi1 {
    status = "disabled";  // change "disabled" to "okay"

Locate uart4's definition in the rk3399-nanopi4-common.dtsi file:

&uart4 {
    status = "okay";   // change "okay" to "disabled"

Compile kernel:

./ -K -M

Use the newly generated "rockdev/Image-nanopc_t4/resource.img" image file to update your system. Testing SPI

By default the SPI is not enabled in your system. You need to manually enable it by making changes to your Android source code:
vendor/friendlyelec/apps# vi
Remove the comment:


Compile Android source code

We connected a FriendlyElec's OLED module which had a 0.96" LCD with a resolution of 128 x 64 and a SPI interface to a NanoPC-T4 and tested it.

The LCD module had 7 pins and here is hardware setup:

OLED Pin Function NanoPC-T4 Pin Comment
DO SCLK Pin23 (SPI1_CLK(3V) Clock generated by master device
DI MOSI Pin19 (SPI1_TXD) Output from master device and input to slave device
RES Pin16 (GPIO1_C6(3V))
D/C Pin12 (GPIO1_C2)
CS CS0 Pin24 (SPI1_CSn0) Signal to enable slave device, set by master device

6.8.2 APIs for Accessing SPI

For more details refer to:FriendlyThings APIs

7 Download Links to Code Samples

All the code samples are included in FriendlyElec's Android source code and are under the "vendor/friendlyelec/apps" directory in Android7.1.2 and Android8.1. Or you can download individual code samples. Here is a list of code samples and their download links:

7.1 Android8.1

7.1.1 Applicable Boards

  • NanoPC-T4/NanoPi-M4/NanoPi-NEO4
Android8.1 Demos
Serial Port






Watch dog


7.2 Android7.1.2

7.2.1 Applicable Boards

  • NanoPC-T4/NanoPi-M4/NanoPi-NEO4
Android7.1.2 Demos
Serial Port






Watch dog