# Unable to use TELEM2 on CUAV V6X

**URL:** <https://discuss.px4.io/t/unable-to-use-telem2-on-cuav-v6x/33947>\
**Category:** PX4 Autopilot\
**Created:** [August 24, 2023, 6:51am UTC](https://discuss.px4.io/t/unable-to-use-telem2-on-cuav-v6x/33947 "2023-08-24T06:51:08Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![TianmingLi](https://discuss.px4.io/user_avatar/discuss.px4.io/tianmingli/32/3744_2.png) [@TianmingLi](https://discuss.px4.io/u/TianmingLi)\
**Post date:** [August 24, 2023, 6:51am UTC](https://discuss.px4.io/t/unable-to-use-telem2-on-cuav-v6x/33947/1 "2023-08-24T06:51:08Z")

</div>

V6X has several serial port [Serial Port Mapping](https://docs.px4.io/main/en/flight_controller/cuav_pixhawk_v6x.html#serial-port-mapping)

So far, I tried TELEM3, UART4, they all worked for mavlink or ros2 communication.

But TELEM2 not works.

By `param show -a`

```auto
x SER_TEL1_BAUD [853,1424] : 57600
    SER_TEL2_BAUD [-1,1425] : 921600
    SER_TEL3_BAUD [-1,1426] : 57600

```

the default SER\_TEL2\_BAUD is 921600. So start mavlink at default baud rate

```auto
mavlink start -d /dev/ttyS4

```

it not works.

Change baud rate to 57600, then start mavlink on

```auto
param set-default SER_TEL2_BAUD 57600

reboot 

param set SER_TEL2_BAUD 57600

mavlink start -d /dev/ttyS4

```

still not works.

Just can not figure out what’s the different between TELEM2 and other UART like TELEM1 or TELEM3

---

<div class="post-metadata">

**Author:** ![Benja](https://discuss.px4.io/user_avatar/discuss.px4.io/benja/32/11872_2.png) [@Benja](https://discuss.px4.io/u/Benja)\
**Post date:** [October 6, 2023, 2:22pm UTC](https://discuss.px4.io/t/unable-to-use-telem2-on-cuav-v6x/33947/2 "2023-10-06T14:22:01Z")

</div>

Hi @TianmingLi  
Did you solve your issue?

TELEM2 is by default used as MAVLINK instance, did you disabled it before starting it manually?