Using Only a Stock Raspberry Pi ZeroW and USB Cable

A Raspberry Pi Serial Gadget makes it so when you plug in the Raspberry Pi Zero to your computer, it will pop up as a Serial Port. You can use the Raspberry Pi with any computer and operating system and it doesn't require special drivers or configuration.

The setup process for the Serial Gadget only has to be done once. The Tuya-Convert software can be updated independently of this setup (requires setting up Wi-Fi for accessing the Internet).

Serial Interface Setup

• Download and flash the latest Raspbian Lite on a microSD card After burning the SD card, the SD flasher may automatically eject it from your computer. If so, remove the SD card and reinsert it to mount it again.
• Edit config.txt & cmdline.txt
  • Find the partition labeled boot and open that folder
  • Use a text editor to open config.txt
  • Go to the bottom and add dtoverlay=dwc2 (no quotation marks) as the last line in the file
  • Save the file as plain text
  • Use a text editor to open cmdline.txt
  • After rootwait, add a space and then modules-load=dwc2,g_serial (no quotation marks)
  • Save the file as plain text
• Create a new text file on the SD card named wpa_supplicant.conf
  • Add the following lines:

    ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
    update_config=1
    country=US
    network={
        id_str="HOTSPOT NAME"
        ssid="SSID"
        psk="PASSWORD"
        key_mgmt=WPA-PSK
    }
    

    • If your Wi-Fi SSID is hidden, add scan_ssid=1 to the network section
• Enable SSH

  • Create a new file on the SD card named ssh
    The contents of the ssh file don’t matter. When the Raspberry Pi first boots, it looks for this file. If it finds it, it will enable SSH and then delete the file.

    Windows:
    C:\> <d>: (where 'd' is the drive letter of the SD card)
    <d>:\> copy nul ssh

    Linux/MacOS:
    $ cd /Volumes/boot
$ touch ssh

• Remove the SD card from the computer by using the proper eject procedure
• Connect to your Raspberry Pi using SSH over Wi-Fi
  • Insert the SD card in the Raspberry Pi
  • Power up the Raspberry Pi using the microUSB connector labeled PWR. Once it boots, it should be connected to your Wi-Fi network
  • Find its IP address in the router and connect to the Raspberry Pi via SSH
  • Log in with user ID pi; password raspberry
  • Encode the Wi-Fi free text password
    wpa_passphrase "SSID" "PASSWORD" | sudo tee -a /etc/wpa_supplicant/wpa_supplicant.conf > /dev/null
    where SSID and PASSWORD are your network's Wi-Fi credentials
  • Edit wpa_supplicant.conf to remove the free text password
• Set up the Raspberry Pi ZeroW Serial Gadget to accept logins

  • Run sudo dmesg to verify that it bound the g_serial driver

  • Enable the tty service
    $ sudo systemctl enable getty@ttyGS0.service

    Created symlink /etc/systemd/system/getty.target.wants/getty@ttyGS0.service → /lib/systemd/system/getty@.service.

    $ sudo reboot

  • After the Raspberry Pi reboots, connect to it via SSH again and verify that the service is running:
    $ sudo systemctl is-active getty@ttyGS0.service

    active

• Shut down the Raspberry Pi
  $ sudo shutdown now

Connect to the Raspberry Pi using the Serial Gadget

• Ensure that your USB cable is data cable and not just a USB power cable. Plug in the USB cable from your computer to the Raspberry Pi microUSB connector labeled USB, not the PWR connector.

  • On your computer you'll see a new Serial port is created

    Windows:
    COMN (where N can be any number)

    Linux/MacOS:
    /dev/tty.usbmodemNNNN
    The NNNN number after usbmodem will vary. Check your /dev folder for the actual device name

• Use a serial terminal emulator application (e.g., PuTTY)

  • Select the port and configure it for 115200 baud, 8N1 (8-bit No-parity 1-stop) (e.g., using PuTTY)

  • Connect to the Raspberry Pi and log in You may have to hit return a few times to get it to come up with the login prompt.

    • On MacOS, the following command may help establish a successful session window:
      screen -L /dev/cu.usbmodemXXXX 115200

      • The XXXX number after usbmodem will vary. Check your /dev folder for the actual device name
      • The -L option turns output logging on for this window

  You are now connected to your Raspberry Pi ZeroW via the USB cable.

Tuya-Convert Installation

⚠️ ⚠️ Installing software packages requires a connection to the Internet (i.e., Wi-Fi) ⚠️ ⚠️

• Update Raspbian packages
  $ sudo apt-get update && sudo apt-get -y upgrade
• Install git to clone the GitHub repository
  $ sudo apt-get install git
• Install and configure Tuya-Convert

  $ git clone https://github.com/ct-Open-Source/tuya-convert
  $ cd tuya-convert
  $ ./install_prereq.sh
  

• The Wi-Fi interface (wlan0) is now freed up for Tuya-Convert to use to flash your Tuya smart devices.
  You will connect to the Raspberry Pi with the wired USB Serial Gadget and will no longer want it to connect to your Wi-Fi network automatically. Disable your Wi-Fi network configuration by renaming the Wi-Fi configuration file:
  sudo mv /etc/wpa_supplicant/wpa_supplicant.conf /etc/wpa_supplicant/wpa_supplicant.conf-saved

Optional Housekeeping

• Disable SSH

  $ sudo service ssh stop
  $ sudo systemctl disable sshd.service (Buster)
  $ sudo systemctl disable ssh.service (Stretch)
  

Using Tuya-Convert

• Invoke the Tuya-Convert flashing script as usual to flash your Tuya smart devices:

  $ cd tuya-convert
  $ ./start_flash.sh
  

• After flashing your Tuya devices, be sure to shut down the Raspberry Pi properly:
  $ sudo shutdown now

Updating the Tuya-Convert Scripts

• The Raspberry Pi will need to connect to the Internet. Connect to the Raspberry Pi via the Serial Gadget and enable the connection to your Wi-Fi network:
  cp /etc/wpa_supplicant/wpa_supplicant.conf-saved /etc/wpa_supplicant/wpa_supplicant.conf
• Reboot the Raspberry Pi:
  $ sudo reboot
• Repeat the Tuya-Convert installation procedure

Thank you to @SourPickel (Discord) for bringing this to the community's attention.