How to First-Boot a Raspberry Pi Zero W via TTL — No SSH

This tutorial focuses on how to successfully connect to a Raspberry Pi using nothing but a USB-to-TTL adapter, even when there's no network connection available.

Step 1 : Connecting the USB-to-TTL adapter to a computer for testing

The cable used this time is built around Prolific's USB-to-UART (TTL) chip, released in 2012. Due to its age, this chip is no longer supported by drivers on Windows 11.

We therefore need to download an older driver and install it in place of the newer one in order to get it working on Windows 11.

Once the update is complete, it will work successfully.

Step 2 : Flashing the Raspberry Pi OS image

Since the Raspberry Pi used this time is the lower-performance Pi Zero W (Gen 1), we chose to flash Raspberry Pi OS Lite, which only has a text-based interface, with no desktop environment.

One issue with choosing OS Lite is that it doesn't come with UART connection (USB-to-TTL) enabled by default. You have to manually locate the

config.txt

file in the boot partition of the SD card and add the line

enable_uart=1

to enable UART connectivity.

Step 3 : Wiring the USB-to-TTL Adapter

The USB-to-TTL adapter only needs three wires connected to the Raspberry Pi Zero W's GPIO header:

• GND connects to the Pi Zero W GND pin
• TXD (adapter's transmit pin) connects to the Pi Zero W RXD pin (GPIO 15)
• RXD (adapter's receive pin) connects to the Pi Zero W TXD pin (GPIO 14)

Note that TX and RX must be cross-connected — the adapter's TX goes to the Pi's RX, and the adapter's RX goes to the Pi's TX. Connecting them straight (TX to TX, RX to RX) will result in no signal at all. Do not connect thePL2303HXApower line (3.3V or 5V) at all — only these three wires are needed.

Step 4 : Download PuTTY

Plug the PL2303HXA into your laptop. Up to this point, do not connect the Raspberry Pi to power yet.

PuTTY is used to establish a serial (TTL) connection with the Raspberry Pi, allowing us to access and control it through a command-line interface over the USB-to-TTL connection.

Opening PuTTY brings up the following screen. We need to select "Serial, " enter the port number seen earlier in Device Manager (e.g., COM3), and set the speed to 115200.

Step 5 : Begin connecting to the Raspberry Pi Zero W

After connecting the Raspberry Pi Zero W to power, you can see the Raspberry Pi's initial boot messages appear in the PuTTY window.

Connection successful, now you're ready to start building all kinds of projects!