Garbage Data On EZ-B UART With GPS

The behavior you’re seeing usually points to signal integrity/noise, not the Serial Terminal skill itself.

A few important notes for the EZ-B v4 / AdventureBot:

1) UART level compatibility

The EZ-B v4 digital pins are 3.3V logic, so a 5V GPS TX line into EZ-B RX is not recommended.
Even if it sometimes works, it can cause unreliable reads and potential long-term issues.

Best practice:

• Use a level shifter or at least a resistor divider from GPS TX EZ-B RX
• GPS RX can usually accept the EZ-B’s 3.3V TX fine, but check the GPS module specs

So yes - for a 5V GPS module, level shifting is the right move.

2) Why it gets worse when the motors move

That’s a classic sign of:

• motor EMI/noise
• power rail sag
• ground bounce
• long/unshielded UART wiring picking up interference

Even if the GPS works on the PC USB dongle, the AdventureBot environment is noisier when the drive motors are active.

3) Serial Terminal settings

For a continuous GPS stream, there usually aren’t special Serial Terminal settings that "fix" garbling in EZ-B Terminal mode.

Things to verify:

• UART is initialized at 9600
• Flow control = None
• no extra line-ending options are needed for reading NMEA sentences
• make sure nothing else in ARC is also using that UART

If you want to test the UART directly, a simple ARC script using UART.initHardwareUart() and UART.hardwareUartReadStringAvailable() is often better for debugging than the terminal view.

4) Wiring / power recommendations

For the AdventureBot, I’d suggest:

• Power the GPS from a clean regulated 5V source
• Keep a common ground with the EZ-B
• Add the level shifter/divider on GPS TX
• Keep UART wires short
• Route UART wires away from motor wires
• Add a larger bulk capacitor near the GPS module and/or EZ-B power input
  • 100 F is okay, but I’d also consider 220-470 F
• If possible, add 0.1 F ceramic decoupling close to the GPS module too

5) Recommended setup

For reliability, I’d do this:

• GPS TX resistor divider/level shifter EZ-B RX (D6)
• EZ-B TX (D5) GPS RX if needed
• Power GPS from regulated 5V
• Common ground
• Short twisted pair wiring if possible
• Keep motor wiring separated

6) Best way to confirm in ARC

Try reading the raw UART data in a small script instead of only the Serial Terminal display.

Example in JavaScript:

UART.initHardwareUart(0, 9600)

while (true) {
  var data = UART.hardwareUartReadStringAvailable(0)
  if (data.length > 0) {
    print(data)
  }
  sleep(100)
}

If the data is still garbled when the motors run, that further confirms a hardware noise / level issue rather than ARC settings.

Bottom line

Most likely fix:

1. Do not feed 5V TX directly into EZ-B RX
2. Use a level shifter or divider
3. Improve power filtering and wiring layout
4. Keep UART wires short and away from the motors

Helpful links

• Serial Terminal skill: https://synthiam.com/Support/Skills/Communication/Serial-Terminal?id=16071
• ARC robot skills and configuration menu info: https://synthiam.com/Support/ARC-Overview/port-selection

If you want, I can help you wire the NEO-6M to the AdventureBot EZ-B v4 pin-by-pin and suggest exact resistor values for a divider.