Electrical Characteristics of Air Prime Dev Kit? Blackouts!

Hi everyone,

I need to connect a STM32L0 Nucleo Board via UART to the Air Prime Dev Kit TXD and RXD, UART1. The STM is supposed to send raw data to the HL which then builds the TCP frames and sends it to a server via GPRS.

The problem is, as soon as I connect the serial port (TXD, RXD, Gnd) I experience blackouts of the Air Prime Board. Almost all LEDs start blinking every few seconds. This could happen due to different logic levels, I guess.

Where can I find electrical characteristics of the Air Prime Board, especially concerning the UART connections? Or do you guys have an idea what’s wrong?

Thank you very much in advance and Happy New Year, btw. :slight_smile: