Third UART


Is someone already succeed in simulating a UART TX line on a GPIO ?

What’s your feeling in trying such development with OpenAT


Maybe with extremely slow speed, but it’s really not worth trying.
On Q2686 you have USB, and if you can’t use USB, it’s better to use an USB host to serial chip like those offered by

Or you go for a SPI or I2C to serial converter if you think that’s better.

Another option is to use the multiplexing capabilities of the UARTs so you can use 4 virtual UARTs on a single physical.

Or if the communication is not needed all the time, you can add a physical multiplexer that you can use to switch between the targets and only use a single UART on the Wavecom module.

Thanks Tobias, not exactly what i’m looking for, but interresting !

Perhaps if you explained exactly what you are looking for, then people might be able to make better suggestions… :question:

What is your actual requirement?

OK… sorry…

Just looking to simulate a TX pin (like a TX on UART) to transmit data at a rate of 9600 bps. Only that pin is necessary. So, for you, what should be the right way to get such behaviour. Using a GPIO ? or something else…

Is there any reason why you can’t use the UART options that are already there?

That’s not really what I meant.

Why do you need to do this?

You’re suggesting a solution - but what is the actual problem?
What are you trying to achieve?


Thanks for your enthusiasm answers.

Yes, there is a good reason! The 2 others are already used by the design itself, around my wireless CPU. As there is a third element on my platform, i need it. But, on this latest element, i just need to transmit data to it. So, i was looking to a simple way to send the data stream. But it seems, that it is not as trivial as i thought :frowning:

Anyway, as i have few available I/O, i primary prefer to use some of those pins rather than using some kind of switch for the TX pin of the UART.

May that was not a great idea :wink:


Maybe multiplexing with Xilinx CPLD? Cheap (few dollars) and fast little monsters, and you can program and manage your connections and change it whenever or whatever you want! You can solve your issue with that.
Worth considering in every complex design!

Best Regards,


Which is exactly what this device does, as it happens: … b&Trail=93

Hum… not possible, but thanks for the idea… i’m afraid of the power consumption of such chip !

Don’t worry… i’ll find an other way…

They don’t call them Cool-Runner” for nothing, you know… :wink:

You wouldn’t need a big powerful device just to do this…

Don’t worry it won’t heat up the room! :slight_smile:

Just don’t forget to post it! :wink:


Anyway, thank you guys !