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(libfriendlyarm-things.so), as shown below:

Android 12 (rk3568 & rk3588)

BSP source code download link: http://112.124.9.243:3000/friendlyelec/rk35xx-android12
Latest ROM download link: http://download.friendlyelec.com/NanoPC-T6

Android 7.1.2-rk3399

BSP source code download link: https://gitlab.com/friendlyelec/rk3399-nougat
BSP source code location on the network disk: sources/rk3399-android-7.git-YYYYMMDD.tgz
Latest ROM download link: http://download.friendlyelec.com/NanoPC-T4

Android 8.1-rk3399

BSP source code download link: https://gitlab.com/friendlyelec/rk3399-android-8.1
BSP source code location on the network disk: sources/rk3399-android-8.1.git-YYYYMMDD.tgz
Latest ROM download link: http://download.friendlyelec.com/NanoPC-T4

3 List of Applicable Boards

FriendlyThings SDK(libfriendlyarm-things.so) 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 libfriendlyarm-things.so in APP

Clone the following library locally:

git clone https://github.com/friendlyarm/friendlythings-sdk

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):

YourProject/
├── AndroidManifest.xml
├── libs
│   ├── arm64-v8a
│   │   └── libfriendlyarm-things.so
│   └── armeabi
│       └── libfriendlyarm-things.so
├── src
│   └── com
│       └── friendlyarm
│           ├── FriendlyThings
│           │   ├── BoardType.java
│           │   ├── FileCtlEnum.java
│           │   ├── GPIOEnum.java
│           │   ├── HardwareControler.java
│           │   ├── SPIEnum.java
│           │   ├── SPI.java
│           │   └── WatchDogEnum.java

Import the following components and the major APIs are included in the HardwareControler.java 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 Android.mk 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:

android:sharedUserId="android.uid.system"

4.2.2 Modify Android.mk

Create an Android.mk file(the simplest way is to copy a sample Android.mk file), modify the Android.mk 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_PACKAGE_NAME := Project Name
 
LOCAL_CERTIFICATE := platform
LOCAL_MODULE_TAGS := optional
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 "setenv.sh" 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
. setenv.sh
cd vendor/friendlyelec/apps/GPIO_LED_Demo
mm

4.4 Sample project in Android Studio

https://github.com/friendlyarm/AndroidStudio-GPIODemo

5 APIs in libfriendlyarm-things.so 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.
HardwareControler.select   //polls a serial port's status and checks if it has data to be read or if data can be written to it.
HardwareControler.read     //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:

6.4.3.1 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

6.4.3.2 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)
Pin4	VCC5V0_SYS
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 = HardwareControler.open("/dev/watchdog", FileCtlEnum.O_WRONLY);
HardwareControler.write(mWatchDogFD, "a".getBytes());

6.8 SPI

6.8.1 RK3399

6.8.1.1 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:

cd ANDROID_SOURCE/kernel
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:

cd ANDROID_SOURCE/
./build-nanopc-t4.sh -K -M

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

6.8.1.2 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 device-partial.mk
Remove the comment:

# PRODUCT_PACKAGES += SPI-OLED

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
GND		Pin6 GND
VCC		Pin2 VCC5V
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