# UART 2 multiplexed

**URL:** <https://forum.sierrawireless.com/t/uart-2-multiplexed/2866>\
**Category:** Open AT\
**Created:** [January 26, 2009, 3:20pm UTC](https://forum.sierrawireless.com/t/uart-2-multiplexed/2866 "2009-01-26T15:20:20Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![dsanchez](https://avatars.discourse-cdn.com/v4/letter/d/eada6e/32.png) [@dsanchez](https://forum.sierrawireless.com/u/dsanchez)\
**Post date:** [January 26, 2009, 3:20pm UTC](https://forum.sierrawireless.com/t/uart-2-multiplexed/2866/1 "2009-01-26T15:20:20Z")

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Hi,

I’m using Q2686H starter kit (with OS 6.10.05 and Firmware R72\_00).

I need to establish com with 2 serial devices and I want to use the uart1 for debug/download purpose (because it is by default on Q26 board).  
But Q26 provides 2 uart and not 3.

How can I do ?

Try to use multiplex on UART 2 ? Is the adl provide function to manage such a multiplex ? But what happens if the 2 devices want to communicate with the board at the same time ?

Sorry if the questions are stupid but I’m newbie and I need to learn 🙂 …

THank’s

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**Author:** ![awneil](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@awneil](https://forum.sierrawireless.com/u/awneil)\
**Post date:** [January 26, 2009, 8:19pm UTC](https://forum.sierrawireless.com/t/uart-2-multiplexed/2866/2 "2009-01-26T20:19:31Z")

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> [@dsanchez](#):
>
> Try to use multiplex on UART 2 ? Is the adl provide function to manage such a multiplex ?

Not directly - you would have to implement it yourself.

> [@](#):
>
> But what happens if the 2 devices want to communicate with the board at the same time ?

Obviously, you have to provide the external multiplexing hardware yourself!

Alternatively, UART chips are available with I2C and SPI interfaces…

Note that you can still use a UART for debug and still have it connected to external devices - see: [viewtopic.php?f=53&t=2509&p=11123#p11123](http://www.wavecom.com/modules/movie/scenes/forums/viewtopic.php?f=53&t=2509&p=11123#p11123)

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**Author:** ![dsanchez](https://avatars.discourse-cdn.com/v4/letter/d/eada6e/32.png) [@dsanchez](https://forum.sierrawireless.com/u/dsanchez)\
**Post date:** [January 27, 2009, 7:27am UTC](https://forum.sierrawireless.com/t/uart-2-multiplexed/2866/3 "2009-01-27T07:27:17Z")

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Thank you !

Just another question; it is possible to simulate uart (9600 baud for example) throught a set of gpio ?

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**Author:** ![awneil](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@awneil](https://forum.sierrawireless.com/u/awneil)\
**Post date:** [January 27, 2009, 9:03am UTC](https://forum.sierrawireless.com/t/uart-2-multiplexed/2866/4 "2009-01-27T09:03:41Z")

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> [@dsanchez](#):
>
> it is possible to simulate uart (9600 baud for example) through a set of gpio ?

No, not under Open-AT - it’s not that “real” time

Note that it is also possible to use the USB connection to the PC for debugging - but that falls apart whenever the unit restarts… ☹