I have been trying to get a serial connection from the J9 socket of a 5G hat to a PixHawk 4. However, there does not seem to be any data going through ttyHS2.

I triple checked to make sure my physical connection is correct and the wires are in the correct area. They look correct to me.

I have the JST from the J9 socket connected to TELEM2 of the PixHawk 4. The baudrate is set to 921600.

The way I am testing this is by using mavlink-router. I run this command:

mavlink-routerd /dev/ttyHS2:921600 -e {my ip}:14550 -v

It has worked before when connecting to the usb port on the hat via an FTDI cable, but we're trying to get it working with the serial port.

I also decided to follow this to see if I could get anything from sending stuff to the port. I saw nothing. But I could be completely wrong that this is a valid way of testing the connection:

(In one terminal):

cat -v < /dev/ttyHS2

(In another terminal):

echo -ne '\033[2J' > /dev/ttyHS2

I did not see anything on the first terminal.

Also, I tried using voxl-mavlink-server to test this. I am on a beta platform (system-image: 1.5.5-M0054-14.1a-perf), so options are a little bit different than what I'm used to.

I had this set as my configuration file:

{
        "primary_static_gcs_ip":        "192.168.8.10",
        "secondary_static_gcs_ip":      "192.168.8.11",
        "onboard_port_to_autopilot":    14556,
        "onboard_port_from_autopilot":  14557,
        "gcs_port_to_autopilot":        14558,
        "gcs_port_from_autopilot":      14559,
        "en_external_uart_ap":  false,
        "autopilot_uart_bus":   2,
        "autopilot_uart_baudrate":      921600,
        "en_external_ap_timesync":      1,
        "en_external_ap_heartbeat":     1,
        "udp_mtu":      0,
        "gcs_timeout_s":        4.5
}

I believe "autipilot_uart_bus" was what I had to set to 2 to get it to go through ttyHS2. I could not see any data passing through though.

I am curious what the problem could be. Any help would be much appreciated.