My M5Unit version of GPS (based on the AT6558) returns always an "Antenna open" text as GPTXT message.
From the AT6558 specification I would expect an "Antenna ok" after a short time if the antenna is connected and "Antenna open" without antenna. I assume the internal antenna is connected to the MAX2659. There are other NMEA messages and after a while I received a GNGGA message.
Any ideas?

Michael