DeskPi Lite (deskpi_v1)

Description

The DeskPin V1 Case is a case made of ABS, and an adapter board is provided inside to transfer the HDMI interface, 3.5mm audio interface, and USB-C power interface of the Raspberry Pi to the back of the panel. and offer microHDMI to Full-sized HDMI interface, makes it convenient for users to use standard HDMI cables to connect external display devices. In addition, it provides an ultra-thin aluminum alloy heat sink and supports an adjustable-speed ultra-thin silent fan, which can be safely cut off Power supply for Raspberry Pi by sending a "power_off" signal to the adapter board.

Features

• Convert the microHDMI to a Full-sized HDMI interface and place it on the back of the panel with the power interface
• Transfer 3.5mm audio interface to the back of the panel
• Support Raspberry Pi official fan temperature control function via raspi-config tool.
• Support system shutdown to safe cut off power on Raspberry Pi
• Support adjustable fan speed via PWM programming.
• Easy to install
• Light weight heat-sink inside.
• Adjustable speed Fan

Product Links: https://deskpi.com

Principle

• RPi -> sending poweroff to /dev/ttyUSB0 means sending cut off power-> MCU on board: means MCU will cut of power of Raspberry Pi.

• RPi <- Reading poweroff from /dev/ttyUSB0 means shutdown system <- MCU on board: system will execute shutdown service or reboot (according to scripts definitions) when power button has been pressed twice.

How to enable fan temperature control?

 NOTE: Raspberry Pi OS (Latest) will support this function.

• Open a terminal and typing following command:

sudo raspi-config 

Navigate to Performance Options -> P4 Fan -> Yes -> 14 -> 60 -> yes -> finish -> reboot Raspberry Pi. The fan is support PWM signal control via GPIO14 which is physical pin 12(TXD), it will spinning when the CPU temperature is above 60 degree. and also you can write your code to control the fan via GPIO14, sending PWM signal will trigger the fan spinning.

This case hardware uses direct GPIO header connections for the included PWM capable fan. Like in your bigger DeskPi case software, you could easily change from a /dev/ttyUSB0 to a GPIO PWM fan control service.

For anyone else wanting to implement some form of PWM fan control, please see the included python3 script code below. This will enable:

< 40'c       - Fan 75%, for a minimum of 60sec
40'c to 45'c - Fan 85%, for a minimum of 120sec
> 45'c       - Fan 100%, for a minimum of 180sec

In everyday use, this script offers good temperatrue control, with the CPU temp rarely reaches > 45'c and general fan noise is very low and still keeps good control via the PWM fan vs standard Raspberry Pi OS PWM fan control via /boot/config.txt or raspi-config.

 #!/usr/bin/python3

import RPi.GPIO as GPIO
import time
import subprocess

GPIO.setmode(GPIO.BCM)
GPIO.setup(14, GPIO.OUT)
pwm = GPIO.PWM(14,100)

print("\nPress Ctrl+C to quit \n")
dc = 0
pwm.start(dc)

try:
    while True:
        temp = subprocess.getoutput("vcgencmd measure_temp|sed 's/[^0-9.]//g'")
        if round(float(temp)) >= 45:
            dc = 100
            pwm.ChangeDutyCycle(dc)
            print("CPU Temp:",float(temp)," Fan duty cycle:",dc)
            time.sleep(180.0)
        if round(float(temp)) >= 40:
            dc = 85
            pwm.ChangeDutyCycle(dc)
            print("CPU Temp:",float(temp)," Fan duty cycle:",dc)
            time.sleep(120.0)
        else:
            dc = 70
            pwm.ChangeDutyCycle(dc)
            print("CPU Temp:",float(temp)," Fan duty cycle:",dc)
            time.sleep(60.00)

except KeyboardInterrupt:
    pwm.stop()
    GPIO.cleanup()
    print("Ctrl + C pressed -- Ending program")
    

Then execute it:

python3 fan_control.py

How to enable the USB2.0 in front of panel?

• 1. Install DeskPi v1 driver.
• 2. Add following parameter to /boot/config.txt file manually.

dtoverlay=dwc2,dr_mode=host

DO REMEMBER `reboot` Raspberry Pi to take effect.

How to send power_off signal to adapter board to cut off power?

• Make sure you have already add dtoverlay=dwc2,dr_mode=host to /boot/config.txt file and reboot Raspberry Pi.
• Check if there is a device called /dev/ttyUSB0
• Execute the python demo script in deskpi_v1/drivers/python/safecutoffpower.py
• you may need to install pyserial library.
• Recommend: adding this function after shutdown service, so that it can safely cut off the power of Raspberry Pi.

How to reboot by double click power buttom?

Principle

when you double click the power button, The MCU on expansion board will send three times poweroffpoweroffpoweroff to serial port on raspberry Pi which generate via dwc2 dtoverlay, called /dev/ttyUSB0, and you can capture it via python script and customized your own script to control the shutdown behavior.

• Demo code:

1. Install pyserial library to control serial port.

pip3 install pyserial 

2. Create a file named safe_shutdown.py and paste following code:

import serial
import time
import os


ser = serial.Serial('/dev/ttyUSB0', baudrate=9600, timeout=3)

while True:
    if ser.isOpen():
        data = ser.read(16)
        data = data.decode('utf-8')
        #print(data)
        if 'poweroff' in data:
            print("System will turn off in 3 seconds")
            time.sleep(3)
	    ser.write(b'power_off')
	    ser.write(b'power_off')
            os.system('sudo sync && sudo init 0')
            

3. Execute it:

python3 safe_shutdown.py

You can also change the os.system("sudo reboot") to reboot your Raspberry Pi.