View source for FriendlyThings for Rockchip

[[FriendlyThings for RK3399/zh|查看中文]]<br /><br />
Note: the steps and methods presented here apply to all FriendlyElec's RK3399 based boards. For steps and methods that apply to other platforms refer to  [[FriendlyThings]]
<br />
{{FriendlyThings Introduction}}
{{FriendlyThings AndroidVersion for RK3399}}
{{FriendlyThings Boards for RK3399}}
{{FriendlyThings Installation Guide}}
==APIs in libfriendlyarm-things.so Library==
Refer to this wiki site:[[FriendlyThings APIs]]

==Access RK3399 Based Boards' Hardware under Android==
===Serial Port===
Currently the only available serial port for users is UART4 and its device name is "/dev/ttyS4". Other serial ports are already taken. Here is a list of the serial ports and their functions. If you need more serial ports you can convert USB ports to serial ports:
::{| class="wikitable"
|-
|Serial || Function
|-
|UART0  || used for Bluetooth
|-
|UART1   || used for Gbps Ethernet  
|-
|UART2  || used for serial debug port
|-
|UART3  || used for Gbps Ethernet
|-
|UART4  || available for users and its device name is "/dev/ttyS4" (Note: it is only available in ROMs generated on June 18,2018 or after)
|}

====APIs for Accessing Serial Ports====
<syntaxhighlight lang="c">
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.
</syntaxhighlight>
For more details refer to :[[FriendlyThings APIs]]


===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.<br />
<br />
Here is a list of GPIOs FriendlyElec's RK3399 boards support:
* NanoPC T4
::{| class="wikitable"
|-
| style="background: PaleTurquoise; color: black" | '''Physical Index'''
| style="background: PaleTurquoise; color: black" |'''GPIO Index'''
|-
|Pin11||33
|-
|Pin12||50
|-
|Pin15||36
|-
|Pin16||54
|-
|Pin18||55
|-
|Pin22||56
|-
|Pin37||96
|-
|Pin38||125
|-
|Pin40||126
|}
* NanoPi M4和NanoPi NEO4
::{| class="wikitable"
|-
| style="background: PaleTurquoise; color: black" | '''Physical Index'''
| style="background: PaleTurquoise; color: black" |'''Linux Index'''
|-
|Pin11||33
|-
|Pin12||50
|-
|Pin15||36
|-
|Pin16||54
|-
|Pin18||55
|-
|Pin22||56
|}

====APIs for Accessing GPIO====
<syntaxhighlight lang="c">
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.
</syntaxhighlight>
For more details refer to:[[FriendlyThings APIs]]

====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.<br />
[[File:rk3399-android-gpio.png|frameless|GPIO]]
===ADC===

RK3399 populates three ADC channels 0, 2 and 3 and here is a list of the channels and their corresponding nodes:
::{| class="wikitable"
|-
| style="background: PaleTurquoise; color: black" | '''Channel'''
| style="background: PaleTurquoise; color: black" |'''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
|}

You can access GPIOs like accessing files under Android.

===PWM===
<b>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, <br />
Please refer to: </b>[[Template:RK3399 Android PWMFan]]<br />
<br />
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
<syntaxhighlight lang="bash">
echo 0 > /sys/class/pwm/pwmchip1/export
</syntaxhighlight>
* Control a PWM fan's speed by setting the PWM's period and duty_cycle.
<syntaxhighlight lang="bash">
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
</syntaxhighlight>
====Testing PWM====
Connect a PWM fan(3 pins) to a NanoPC-T4's fan port to test it.
[[File:rk3399-android-pwm.png|frameless|PWM]]

===I2C===

To test I2C we connected a FriendlyElec's LCD1602 module to a NanoPC-T4 and ran the I2C demo program:
::{| class="wikitable"
|-
| style="background: PaleTurquoise; color: black" | '''Physical Index'''
| style="background: PaleTurquoise; color: black" |'''I2C Functions'''
|-
|Pin3||I2C2_SDA(3V)
|-
|Pin4||VCC5V0_SYS
|-
|Pin5||I2C2_SCL(3V)
|-
|Pin6||GND
|}

Here is a hardware setting:<br />
[[File:NanoPC-T4+OLED.jpg|frameless|450px]]

===RTC===
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:<br />
<syntaxhighlight lang="bash">
cat /sys/class/rtc/rtc0/date
# 2018-10-20                                                              
cat /sys/class/rtc/rtc0/time                                            
# 08:20:14
</syntaxhighlight>
Set power-on time. For instance power on in 120 seconds:
<syntaxhighlight lang="bash">
#Power on in 120 seconds
echo +120 >  /sys/class/rtc/rtc0/wakealarm
</syntaxhighlight>
[[File:rk3399-android-rtc.png|frameless|RTC]]

===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:
<syntaxhighlight lang="java">
mWatchDogFD = HardwareControler.open("/dev/watchdog", FileCtlEnum.O_WRONLY);
HardwareControler.write(mWatchDogFD, "a".getBytes());
</syntaxhighlight>
[[File:rk3399-android-watchdog.png|frameless|WatchDog]]

===SPI===
====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:<br />
Edit the DTS file: arch/arm64/boot/dts/rockchip/rk3399-nanopi4-common.dtsi:
<syntaxhighlight lang="c">
cd ANDROID_SOURCE/kernel
vim arch/arm64/boot/dts/rockchip/rk3399-nanopi4-common.dtsi
</syntaxhighlight>
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:
<syntaxhighlight lang="c">
&spi1 {
    status = "disabled";  // change "disabled" to "okay"
</syntaxhighlight>
Locate uart4's definition in the rk3399-nanopi4-common.dtsi file:
<syntaxhighlight lang="c">
&uart4 {
    status = "okay";   // change "okay" to "disabled"
</syntaxhighlight>
Compile kernel:
<syntaxhighlight lang="bash">
cd ANDROID_SOURCE/
./build-nanopc-t4.sh -K -M
</syntaxhighlight>
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:<br />
vendor/friendlyelec/apps# vi device-partial.mk<br />
Remove the comment:<br />
<syntaxhighlight lang="bash">
# PRODUCT_PACKAGES += SPI-OLED
</syntaxhighlight>
Compile Android source code<br />
<br />
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.<br />
<br />
The LCD module had 7 pins and here is hardware setup:<br />
::{| class="wikitable"
|-
| style="background: PaleTurquoise; color: black" | '''OLED Pin'''
| style="background: PaleTurquoise; color: black" |'''Function'''
| style="background: PaleTurquoise; color: black" |'''NanoPC-T4 Pin'''
| style="background: PaleTurquoise; color: black" |'''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
|}
<br />
====APIs for Accessing SPI====
For more details refer to:[[FriendlyThings APIs]]

==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:
{{FriendlyThings Android8 Demos}}
{{FriendlyThings Android7 Demos}}