Serial Setup

Full control of the RS-UV3A requires a serial connection. This guide covers the various ways to connect and configure serial communication.

Connection Options

The RS-UV3A provides three serial connection methods:

Method	Connector	Best For
On-board USB	Micro USB	Most users—single cable for power and control
JP1 Header	0.1” header	Arduino and microcontroller projects
JP2 Header	6-pin header	FTDI cable or Raspberry Pi
DE-9 I/O	DE-9 pins 7/8	External serial devices

Important

JP1 and JP2 share the same internal serial port (B1 baud setting). The DE-9 uses a separate serial port (B2 baud setting).

On-board USB (Recommended)

The RS-UV3A Rev A includes an FTDI FT230X USB-serial chip that works without drivers on most modern operating systems.

Setup Steps

1. Connect a micro USB cable to the RS-UV3A
2. Connect the other end to your computer
3. The board powers on and enumerates as a serial port

Finding the Port

Linux:

ls /dev/ttyUSB*
# or
dmesg | grep tty

macOS:

ls /dev/tty.usbserial*

Windows:

• Open Device Manager
• Look under “Ports (COM & LPT)”
• Note the COM port number (e.g., COM3)

Terminal Software

Use any serial terminal program to communicate with the RS-UV3A:

Platform	Options
Linux	minicom, screen, picocom, putty
macOS	screen, CoolTerm, Serial
Windows	PuTTY, Tera Term, RealTerm
Cross-platform	Arduino Serial Monitor, VS Code Serial Monitor

Connection Settings

Parameter	Value
Baud Rate	19200 (default)
Data Bits	8
Parity	None
Stop Bits	1
Flow Control	None
Line Ending	Carriage Return (CR)

Example: Using screen (Linux/macOS)

screen /dev/ttyUSB0 19200

To exit: Ctrl-A then K, confirm with Y

Example: Using minicom (Linux)

minicom -D /dev/ttyUSB0 -b 19200

Configure: Ctrl-A then O → Serial port setup → Hardware flow control: No

Verifying Connection

Send a command to verify communication:

FW

Expected response:

FW: 2.4A

(Version number may vary)

Try a few more commands:

F?        # Query frequency
SS        # Read signal strength
VT        # Read voltage
TP        # Read temperature

Changing Baud Rate

The RS-UV3A supports multiple baud rates:

Code	Baud Rate
0	1200
1	4800
2	9600
3	19200 (default)
4	38400
5	57600

Internal Serial (USB/JP1/JP2)

B13       # Set to 19200 (default)
B15       # Set to 57600

External Serial (DE-9)

B23       # Set to 19200 (default)
B25       # Set to 57600

Caution

Baud rate changes require a power cycle to take effect. After changing, you’ll need to reconnect your terminal at the new baud rate.

Arduino Connection

To connect the RS-UV3A to an Arduino:

1. Install headers on JP1 (see Connections)

2. Connect:

   • RS-UV3A RXD → Arduino TX pin
   • RS-UV3A TXD → Arduino RX pin
   • RS-UV3A GND → Arduino GND

3. Use SoftwareSerial or hardware UART at 19200 baud

Arduino Example

#include <SoftwareSerial.h>

SoftwareSerial radio(10, 11);  // RX, TX

void setup() {
  Serial.begin(9600);
  radio.begin(19200);

  delay(100);
  radio.println("F?");  // Query frequency
}

void loop() {
  if (radio.available()) {
    Serial.write(radio.read());
  }
}

Logic Levels

The RS-UV3A accepts 3.3V or 5V logic inputs. Output voltage depends on the VIO pin:

• If Arduino VIN powers the RS-UV3A: outputs match Arduino logic
• For 3.3V devices (like Raspberry Pi): jumper JP1 3.3V to JP2 VIO

Raspberry Pi Connection

Connect directly to GPIO UART:

RS-UV3A (JP1/JP2)	Raspberry Pi
TXD	GPIO 15 (RXD)
RXD	GPIO 14 (TXD)
GND	GND
3.3V → VIO	(jumper on RS-UV3A)

Enable UART on Raspberry Pi:

sudo raspi-config
# → Interface Options → Serial Port
# → Login shell: No
# → Serial hardware: Yes

Command Syntax

All RS-UV3A commands follow these rules:

• Not case sensitive — fs146520 equals FS146520
• Terminated by CR — Carriage return (ASCII 13)
• Fixed digit counts — Some parameters require all digits (e.g., FS146520 not FS14652)
• Query with ? — Most commands accept ? to query current value

Quick Command Test

FS146520    # Set frequency to 146.520 MHz
F?          # Query current frequency
SQ5         # Set squelch to level 5
TX1         # Transmit for 1 minute max
TX0         # Stop transmitting

See the Command Reference for the complete command list.

Troubleshooting

No Response to Commands

1. Check USB cable is data-capable (not charge-only)
2. Verify correct COM port
3. Confirm baud rate is 19200
4. Ensure line ending is CR (not LF or CRLF)
5. Check for loose connections

Garbled Output

• Wrong baud rate — try 19200, then other rates
• Line ending issues — try CR only
• Noise on serial line — use shorter cables, add bypass capacitors

USB Not Recognized

• Try a different USB cable
• Try a different USB port
• On Windows, install FTDI drivers if needed
• Check dmesg output on Linux for errors