The schematic mentions the unshifted I2C adress that the GPS module would respond to. When writing or reading to it you need to shift a direction bit in front of it (most significant bit). It’s probably also mentioned in the Titan 1 GPS datasheet. (not sure, only skimmed it) It does not seem to have a way of making it respond to different adresses through pin selection. So multiple modules wil not cooperate on the same I2C bus. An I2C Bus multiplexer chip would be needed. Something like this: https://learn.adafruit.com/adafruit-tca … t/overview