Powering my IoT HAT as standalone via the 5V pin and feeding the digital pins with 3.3V, UART pins 8 and 10 (RX and TX) do not seem to respond. Obviously I also connected the ground. In this setup the HAT is connected to a mesaurement tool where I can associate AT commands to a particular power behaviour.
I have already tried switching TX and RX but nothing happens. I have read somewhere that for particular scenarios you have to solder some jumper. Is this the case? And why is the UART connection via pins working with no problems when the IoT HAT is stacked on top of the Raspberry Pi?
Thank you in advance.