Hi everyone,
I’m trying to use aPL2303TA USB TO TTL (this one: https://easyelecmodule.com/product/pl2303ta-usb-to-ttl/) as a serial console cable to access my Pi’s UART pins, but I’m running into strange behavior and could use some help figuring it out.
Setup
Raspberry Pi 4 running latest Raspberry Pi OS
PL2303TA connected via USB
TTL side wired to Pi’s UART pins: TX(USB-TTL) → RX(Pi), RX(USB-TTL) → TX(Pi), shared ground
USB-serial port shows up as /dev/ttyUSB0 (verified via dmesg)
Baud rate, stop bits, etc. set to match expected console settings (115200-8-N-1)
I can send data from the Pi, but nothing shows up on the TTL side, no echo, nothing. If I try a loopback test on the PL2303TA module (short TX and RX), I see characters OK on my PC, which means the module itself seems physically OK.
When the TTL adapter is plugged in, sometimes the Pi’s boot messages appear garbled, or don’t show at all. Tried different USB ports and cables, but results are inconsistent
Double-checked wire connections, no loose wires. Ensured the Pi’s UART pins are enabled & not being used by Bluetooth or other services (disabled serial-console conflicts) Tested lower baud rates (9600, 57600), still bad or no output. Checked that the ground between Pi and TTL module is solid
Is there a common issue with power supply / USB noise interfering? Could it be a driver issue or firmware for the PL2303TA that’s incompatible with recent Raspberry Pi OS updates? What checks/logs should I look at (e.g. dmesg, uart-config) to find if Pi is rejecting input on the RX pin?
Would really appreciate any tips.
Thanks!
Jordan
I’m trying to use aPL2303TA USB TO TTL (this one: https://easyelecmodule.com/product/pl2303ta-usb-to-ttl/) as a serial console cable to access my Pi’s UART pins, but I’m running into strange behavior and could use some help figuring it out.
Setup
Raspberry Pi 4 running latest Raspberry Pi OS
PL2303TA connected via USB
TTL side wired to Pi’s UART pins: TX(USB-TTL) → RX(Pi), RX(USB-TTL) → TX(Pi), shared ground
USB-serial port shows up as /dev/ttyUSB0 (verified via dmesg)
Baud rate, stop bits, etc. set to match expected console settings (115200-8-N-1)
I can send data from the Pi, but nothing shows up on the TTL side, no echo, nothing. If I try a loopback test on the PL2303TA module (short TX and RX), I see characters OK on my PC, which means the module itself seems physically OK.
When the TTL adapter is plugged in, sometimes the Pi’s boot messages appear garbled, or don’t show at all. Tried different USB ports and cables, but results are inconsistent
Double-checked wire connections, no loose wires. Ensured the Pi’s UART pins are enabled & not being used by Bluetooth or other services (disabled serial-console conflicts) Tested lower baud rates (9600, 57600), still bad or no output. Checked that the ground between Pi and TTL module is solid
Is there a common issue with power supply / USB noise interfering? Could it be a driver issue or firmware for the PL2303TA that’s incompatible with recent Raspberry Pi OS updates? What checks/logs should I look at (e.g. dmesg, uart-config) to find if Pi is rejecting input on the RX pin?
Would really appreciate any tips.
Thanks!
Jordan
Statistics: Posted by Jordan1x — Thu Sep 11, 2025 8:06 pm