# External autopilot not getting serial communication with M0090 board

Source: https://forum.modalai.com/topic/2141/external-autopilot-not-getting-serial-communication-with-m0090-board
Category: VOXL 2 and VOXL 2 Mini (https://forum.modalai.com/category/26/voxl-2-and-voxl-2-mini)
Tags: voxl-2
Posted: 2023-05-09 13:16:24 UTC by andrespalomino
Replies: 7 · Views: 1771

## andrespalomino · 2023-05-09 13:16:24 UTC

Re: [Using M.2 5G Modem Addon Board (M0090) on voxl2]

Hi
My question is quite similar to this previous topic. I'm trying to conect an external autopilot with the Addon Board (M0090) in `J9` pin. The device `/dev/ttyHS2` is available but can not get serial data using mavros (voxl-mavlink-service is disabled). 

I launch in a different voxl2 kit and I am able to get the serial comunication running with the external autopilot. 

The differences are: 

* System working with `voxl-suite: 0.9.5` and `M0090` board with J8 soldered 
* System not working with `voxl-suite: 0.9.4` and `M0090` board with 5G module and mising `J8` (we noticed it was shipped without this J8 pin), could it be a hardware issue? 

Thanks

## Reply by modaltb (ModalAI staff) · 2023-05-09 14:17:02 UTC

Hi @andrespalomino , `J9` on the M0090 board has the UART exposed (see https://docs.modalai.com/voxl2-external-flight-controller/#using-m2-5g-modem-addon-board-m0090) on pins 2/3 and you'll also need GND on pin 6.

J8 exposes GPIO by default or a SPI, so it definitely won't work for a UART...  so don't use `J8`.

Can you post a pic of your M0090?  I don't expect it to be missing J8 connector...   Perhaps J6 is DNI as that is a kernel debug UART not used by most.

## Reply by Vinny (ModalAI staff) · 2023-05-09 19:09:00 UTC

Hi @andrespalomino 
J8 should not be missing on a Voxl2 variant that also has J2.
If you bought a Voxl1 version, then yes, J8 is missing by design.
Can you please send a photo of your M0090 board top and bottom?
If you have the Voxl1 version, most of the extra UART ports are not present.

Thanks!
Vinny

## Reply by andrespalomino · 2023-05-10 07:42:58 UTC

Hi @Vinny and @modaltb 
The picture below shows the board that can not get serial in `/dev/ttyHS2`. I'm using `J9` with pins 2/3 and 6. The cable and serial connection works in a different M0090 board

I mentioned the missing `J8` as a difference from the working board and this one. 5G module and the wifi dongle on the USB works though

Thanks

![Screenshot from 2023-05-10 09-31-59.png](https://forum.modalai.com/assets/uploads/files/1683704024849-screenshot-from-2023-05-10-09-31-59.png)

## Reply by modaltb (ModalAI staff) · 2023-05-11 00:02:01 UTC

@andrespalomino we have manufactured a couple types of the M0090.

There's a VOXL1 based flavor, that only has a single board to board connector on the BOTTOM side of the M0090.

The VOXL2 based flavor has TWO board to board connectors.

Did the M0090 come pre-installed or did you add it yourself?

Can you look under the non-functional board and see if there's 2 board to board connectors?  EG for VOXL2, the J3 and J5 connectors, should both be plugged into.  The UART referenced here is on the "High Speed Board to Board Connector" which is J5 --> https://docs.modalai.com/voxl2-linux-user-guide/#devttyhs2---hsb2b-connector-uart

If you have the VOXL1 version of the M0090, perhaps this is the culprit....

## Reply by andrespalomino · 2023-05-11 10:01:23 UTC

Hi @modaltb 
Thanks for your information. Yes that's the point. The non-funtional board of the picture just have the `J3` board to board connector 

We bought it separately with the following link which states carrier board only for VOXL2 https://www.modalai.com/products/mdk-m0090?variant=40594936463411

I believe I could test `/dev/ttyHS1` connecting to `J12 USB2`? Otherwise, could we start a process to return this board and get the VOXL2 based board

Thanks

## Reply by Vinny (ModalAI staff) · 2023-05-11 18:19:21 UTC (in reply to andrespalomino)

Hi @andrespalomino 
Sorry for your troubles, it looks like we may have sent you a Voxl1 variant by mistake instead of a Voxl2 version.
I'll make sure our operations team gets you a new M0090 board meant for Voxl2, and if possible, we'll include a return shipping label for your Voxl1 version M0090 you have now.

Thanks!
Vinny

## Reply by andrespalomino · 2023-05-15 09:17:14 UTC (in reply to Vinny)

Hi @Vinny 
Sounds good. I have order number 3143. We have the Voxl1 version ready to return.
I'll be here for further instructions 

Thanks
Andres