Serial port not responding

Good morning.
Im developing a solution using the HL6528 modem with socket.
After doing the start up sequence, we are not having response from the modem.
Sometimes we get only an ECHO form the commands sent, but no more.

Here are the Power On, CTS and RX signals.

After 30 seconds, the RX signal always goes down.

Its something bad with the init?

Can you elaborate a little more…


If you are using some voltage level translator chip between the MCU and HL, make sure the reset and on pin is not floating. I pulled mine both to high and the UART interface starts works after that. Those 2 line are connected to an open drain voltage translator chip but left floating at the driving input due to testing for now.