Cube Orange TTL GPS not detected via MAX3232 — need help

Cube Autopilot
1

Hi all,

I am trying to connect an external TTL GPS module to a Cube Orange using a MAX3232 level converter. The MAX3232 is powered by an external 3.3V regulator and GND is common with the Cube.

Connections are:

  • TX of GPS module → RX of Cube GPS1

  • RX of GPS module ← TX Cube GPS1 (not connected for testing)

Cube parameters in Mission Planner are:
SERIAL3_PROTOCOL = 5
SERIAL3_BAUD = 9600
GPS_TYPE = 5
GPS_AUTO_CONFIG = 1
GPS_RATE_MS = 200

The problem:

  • Cube does not detect the GPS. Mission Planner shows No GPS or EKF3 waiting for GPS config data.

  • I can send NMEA sentences from PuTTY, but the screen stays black (normal, Cube only reads the signal).

  • I have tried sending repeated NMEA sentences including GGA and GPRMC, but Cube still does not detect the GPS.

MAX3232 status:

  • Powered with 3.3V external

  • GND is common with Cube

  • Connections verified multiple times

I am not sure if the Cube is receiving the TTL signal correctly, or if there is a firmware / protocol issue.

I have checked:

  • Baud rate matches SERIAL3_BAUD

  • SERIAL3_PROTOCOL = 5, GPS_TYPE = 5

  • GND common, TX module → RX Cube

  • Sent repeated GGA + RMC sentences

I am looking for advice on:

  1. How to confirm Cube is receiving the TTL signal correctly

  2. Any firmware or parameter settings I might be missing

  3. Whether there are known issues with Cube Orange + MAX3232 TTL GPS

Thanks in advance!