I am trying to get a NEO-M8T u-blox receiver to accept configuration commands through UART from a microprocessor however, after a few seconds, it starts to send out a GNTXT NMEA message stating "More than 100 frame errors, UART RX was disabled". I've read through the other posts on this issue and it seems the main two reasons for this would be a low idle on the RX line or a bad ground plane.
I did notice that when I wasn't sending any messages from the micro, the u-blox RX line was in-fact low. I used a 10K resistor to pull up the RX and TX lines (to 3.3V), however the frame errors message remains.
I've also connected the u-blox to my PC through an RS-232 level-shifter to try and get communication working with u-center and I am still seeing the same issue. TX from the u-blox works fine in both applications. I am able to see and parse the default NMEA messages.
Is there something I am misunderstanding in the way these ICs should be integrated? Thanks in advace!