In XPlus_GPIO

Refactoring the XPlus TVBOX to access the GPIO.

<img src="https://github.com/msoyamada/XPlus_GPIO/blob/main/screenshots/logo-unioeste-png-rgb.png" width="270" height="95"> <img src="https://github.com/msoyamada/XPlus_GPIO/blob/main/screenshots/LogoCC-Copia.png" width="100" height="97"> Ciência da Computação - Campus Cascavel

Install the Armbian using the multitool

RK322x tvbox image: https://armbian.hosthatch.com/archive/rk322x-box/archive/

*In this test the Armbian_24.11_Rk322x-box_bookworm was used (Newer versions may also work)

TVBox In XPlus

Specs: SoC RK3229 (4 cores, ARM-V7), 2GB RAM, 8GB Flash) screenshot

RK3229 GPIO

The RK3229 features 4 GPIO controllers with 32 pins each (128 total). Many are used for peripherals like flash, MMC, Wifi, HDMI etc. Based on the work developed in the Instituto Federal de Goiás - Campus Goiânia by Mateus Morais Aguirre and Prof. Dr. Claudio Afonso Fleury, a search for IO ports was performed using the script testgpio.py).

Detected GPIO

| GPIO | Descrição | | ------------- | ------------- | | 0 | GPIO0_A0/I2C0_SCL | | 1 | GPIO0_A1/I2C0_SDA | |41 | GPIO1_B1/UART1_TX/UART2_TX| |42 | GPIO1_B2/UART1_RX/UART2_RX| |96 | GPIO3_A0/SDMMC1_CLKO | |97 | GPIO3_A1/SDMMC1_CMD | |98 | GPIO3_A2/SDMMC1_D0| |99 |GPIO3_A3/SDMMC1_D1| |100 | GPIO3_A4/SDMMC1_D2| |101 | GPIO3_A4/SDMMC1_D2| |102 | GPIO3_A6/UART1_RTSN| |103 | GPIO3_A7/UART1_CTSN|

*Note: The MMC1 ports can be used because the board used only the MMC0 controller for the SD card slot. The pins placement in the board is presented below. screenshot

Physical Access to GPIO Pins

GPIO41 and GPIO42 have pre-drilled holes for easy soldering.
Other GPIOs (e.g., 96 and 99) were accessed via enamel wires and unused holes.
GND and 3.3V power pins are also identified on the board.

screenshot

Software

To access the GPIO(via sysfs):

cd /sys/class/gpio

echo 41 > export

cd gpio41

echo out > direction

echo 0 > value

echo 1 > value

Blinka

Blinka: Blinka brings CircuitPython APIs and, therefore, CircuitPython libraries to single board computers (SBCs). https://circuitpython.org/blinka Popular in Raspberry, this library enables the GPIO access. It has also a set of components to access I2C devices.

Install the packages

apt install gcc
apt install python3-pip
apt install python3-venv
apt install python3-dev
apt install python3-libgpiod
apt install libgpiod2
apt install libgpiod-dev
update-alternatives --install /usr/bin/python python /usr/bin/python3 10

Create a python virtual environment

mkdir rk3229 && cd rk3229
python -m venv .env
source .env/bin/activate

**At each start, execute source .env/bin/activate **

Install the python packages

pip install click 
pip install adafruit-python-shell 
pip install adafruit_blinka 
pip install gpiod

*To install the packages outside a virtual environment, use the parameter --break-system-packages in the pip command. Ex: pip install --break-system-packages

Led Blink

Conection GPIO42 -> LED -> RESISTOR 220 Ohm -> GND

Python code blink.py

The blinka does not have the pin mapping for TVBox devices. We are using the RK3328, it has also 4 GPIO chips and 128 pins.

import os
os.environ["BLINKA_FORCEBOARD"]="ROC-RK3328-CC"
os.environ["BLINKA_FORCECHIP"]="RK3328"

import time
import board
import digitalio
from adafruit_blinka.microcontroller.generic_linux.libgpiod_pin import Pin

In the RK3229 datasheet, the ports codification follows the pattern:

GPIO(X1)_(X2)(X3)

GPIO = 32 ∗ X1 + 8 ∗ X2 + X3.

Values: A = 0, B = 1, C = 2 e D = 3.

Ex:

GPIO1_B2
num= 32*1 + 1*8 + 2
num = 42

In the blinka, follows the pattern (chip, port). To use this codification, we just need to sum 8*X2 + X3, and use as the second parameter. For instance, port 42 is instantiated as pin = Pin((1,10))

pin = Pin((1,10))  # (x,y) = 32*x +y  -> 1*32 + 10 = 42 (GPIO 42)
led = digitalio.DigitalInOut(pin)
led.direction = digitalio.Direction.OUTPUT

Writing in the port

while True:
    led.value = True
    time.sleep(0.5)
    led.value = False
    time.sleep(0.5)

Run

python blink.py

I2C connection

rk3229 has 4 I2C controllers. It was detected the controller 0, using the ports 0 (SCL) and 1 (SDA) (Figure above).

Enabling the I2C controller in DTB

cd /boot
dtc -I dtb -O dts dtb/rk322x-box.dtb > rk322x-box.dts

Edit the file rk3222x-box.dts and enable I2C_0, changing disable for ok in the status field.

       i2c@11050000 {
                compatible = "rockchip,rk3228-i2c";
                reg = <0x11050000 0x1000>;
                interrupts = <0x00 0x24 0x04>;
                #address-cells = <0x01>;
                #size-cells = <0x00>;
                clock-names = "i2c";
                clocks = <0x02 0x14c>;
                pinctrl-names = "default";
                pinctrl-0 = <0x29>;
                status = "okay";
                phandle = <0x78>;
        };

generate the new DTB dtb/rk322x-box.dtb

dtc -I dts -O dtb rk322x-box.dts -o dtb/myrk3222x-box.dtb

edit the file /boot/armbianEnv.txt, field fdtfile

fdtfile=myrk322x-box.dtb

restart the board

To test, connect an I2C device in the SCL and SDA pins, and check if it will be find.

apt install i2c-tools
i2cdetect -y 0

Output example with an OLED (Address 0x3c) e BMP280 (Address 0x76)

(.env) root@rk322x-box:~/rk3229# i2cdetect -y 0
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- 3c -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- 76 --

Edit the file board in Blinka, to use the correct I2C pin (TODO)

cd .env/lib/python3.11/site-packages/adafruit_blinka/microcontroller/rockchip/rk3328/

Edit the file pin.py

# I2C
I2C0_SDA = GPIO0_A1
I2C0_SCL = GPIO0_A0
#I2C1_SDA = GPIO2_A4
#I2C1_SCL = GPIO2_A5


...
...
...

# ordered as i2cId, SCL, SDA
#i2cPorts = ((0, I2C1_SCL, I2C1_SDA),)
i2cPorts = ((0, I2C0_SCL, I2C0_SDA),)

Install circuitpython-ssd1306

OLED

apt install libjpeg-dev
pip install pillow 
pip install adafruit-circuitpython-ssd1306

To test, run the code oled.py

python oled.py

Install circuitpython-bmp280

BMP280 - Pressure and temperature sensor

pip install adafruit-circuitpython-bmp280

To test, run the code bmptest.py

python bmptest.py

Example, reading the data from BMP280 and showing in the OLED display

Code displaybmp.py

Sending data to Internet (Thingspeak)

Create a channel in the Thingspeak

Code displaybmp_thingspeak.py

GPIO Input

Some RK3228 ports have pull up or down resistors, that can be configured by software. Take a look in the datasheet, if the port to be used by the button can be configured. In case it is not possible, it will be necessary to use a pull up ou pull down resistor.

Code readpin.py

import os
os.environ["BLINKA_FORCEBOARD"]="ROC-RK3328-CC"
os.environ["BLINKA_FORCECHIP"]="RK3328"
import time
import board
import digitalio
from adafruit_blinka.microcontroller.generic_linux.libgpiod_pin import Pin

pin = Pin((3,3))  ## Pin 99
pinled = Pin((1,10))  ## Pin 42

button = digitalio.DigitalInOut(pin)
button.direction = digitalio.Direction.INPUT
button.pull = digitalio.Pull.UP

led = digitalio.DigitalInOut(pinled)
led.direction = digitalio.Direction.OUTPUT

while True:
    led.value = button.value
    #print(button.value)
    time.sleep(0.1)

Using the keypad component

import os

os.environ["BLINKA_FORCEBOARD"]="ROC-RK3328-CC"
os.environ["BLINKA_FORCECHIP"]="RK3328"

import time
import board
import digitalio
from adafruit_blinka.microcontroller.generic_linux.libgpiod_pin import Pin

import keypad
button=Pin((3,3)) #Pin 99
keys = keypad.Keys((button,), value_when_pressed=False, pull=True)

while True:
    event = keys.events.get()
    # event will be None if nothing has happened.
    if event:
        print(event)

Hints

Installing the GUI

apt install xfce lightdm xorg

GUI in python

There are many options. For instance PySimpleGUI

apt install python3-tk

pip install pysimplegui

NOT WORKING YET

The CircuitPython is working with the devices used in this tutorial. However, some sensor type uses a proprietary protocol. For instance, the DHT sensor uses a 1-wire proprietary protocol. The protocol requires a time sample in us (microseconds), which in the case of a time sharing OS like Linux, it is hard to guarantee.

pip install adafruit-circuitpython-dht

In the tests performed, in most of cases the reading returns a error due to missing bits (dht.py). Putting the scaling_governor in performance mode (maximum processor frequency), some readings were ok (about 10%). In this case the SoC performance is the problem.

cd /sys/devices/system/cpu/cpu1/cpufreq
echo performance > scaling_governor

Pinning the execution in the core 0x2

taskset 0x2 python dht.py

TODO

Creat

XPlusGPIO

Install / Use

README