# Issue Getting uart Connection on VOXL2 to PixHawk4 on 5G Hat

Source: https://forum.modalai.com/topic/2354/issue-getting-uart-connection-on-voxl2-to-pixhawk4-on-5g-hat
Category: VOXL 2 and VOXL 2 Mini (https://forum.modalai.com/category/26/voxl-2-and-voxl-2-mini)
Tags: voxl-2
Posted: 2023-06-29 19:09:54 UTC by John Nomikos 0
Replies: 7 · Views: 1901

## John Nomikos 0 · 2023-06-29 19:09:54 UTC

Good afternoon,

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](https://unix.stackexchange.com/questions/117037/how-to-send-data-to-a-serial-port-and-see-any-answer) 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.

## Reply by wilkinsaf · 2023-06-29 22:22:06 UTC

For context, the UART/USB addon board is working (https://docs.modalai.com/voxl2-usb3-uart-add-on-user-guide/)
and we are using cables provided by ModalAI. So, it appears that it is just the 5G modem carrier board that is not letting this through

## Reply by wilkinsaf · 2023-06-29 22:25:06 UTC (in reply to wilkinsaf)

for context as well, here are the serial devices by-id page. All of them are from Quectel. 
![64b71271-9119-42e2-aba2-05d9583496b9-image.png](https://forum.modalai.com/assets/uploads/files/1688077464622-64b71271-9119-42e2-aba2-05d9583496b9-image.png) 

Dont think that matters, but just trying to add context. 

Also, the 5G carrier board is operational. We see the wwan0 interface

## Reply by wilkinsaf · 2023-06-29 22:36:26 UTC (in reply to wilkinsaf)

https://forum.modalai.com/topic/2141/external-autopilot-not-getting-serial-communication-with-m0090-board/8?_=1688077180364

I think this might be the issue

![15e886bc-dcf2-4240-91c6-4c5e34ceba35-image.png](https://forum.modalai.com/assets/uploads/files/1688078197479-15e886bc-dcf2-4240-91c6-4c5e34ceba35-image.png)

## Reply by tom (ModalAI staff) · 2023-06-30 03:19:38 UTC (in reply to wilkinsaf)

@wilkinsaf That must be the VOXL1 flavor

## Reply by wilkinsaf · 2023-06-30 04:34:23 UTC (in reply to tom)

@tom Damn.... welp... that would explain what's going on. 
Back to the ModalAI store. Thanks for confirmation Tom

## Reply by wilkinsaf · 2023-07-06 17:33:12 UTC (in reply to wilkinsaf)

Can confirm ordering and installing a new one fixed our issue

## Reply by tom (ModalAI staff) · 2023-07-06 18:03:15 UTC (in reply to wilkinsaf)

@wilkinsaf Thanks for the feedback