user77314: guys. I need your help. I have 6 Serial Channels and I need to listen this channel and be sure which channel is working? How can I do that? Can I listen this channel by using digital inputs? Or Do I have to use a devices which has a 6 Serial ports? Like 2 Arduino Mega?

user4143: For your needs you don't need actual UARTs. You can do it all with normal GPIO pins and one (or more) interrupts.
UART communication is characterised by having a "start bit" at the beginning of all bytes. That is, in TTL terms, a transition from HIGH to LOW. You just need to look out for that transition.
You could:

Use Pin Change interrupts on 6 pins to monitor for any FALLING transistion, or
Use one interrupt pin with a wired OR of all the signals along with individual pins for each signal to determine which triggered the interrupt.

To determine "is it active" you just need to know that an interrupt has occurred and which pin triggered it, and has that been seen within a certain time period (to be decided by you).

77314: <p>guys. I need your help. I have 6 Serial Channels and I need to listen this channel and be sure which channel is working? How can I do that? Can I listen this channel by using digital inputs? Or Do I have to use a devices which has a 6 Serial ports? Like 2 Arduino Mega?</p>
 4143: <p>For your needs you don't need actual UARTs. You can do it all with normal GPIO pins and one (or more) interrupts.</p>
<p>UART communication is characterised by having a &quot;start bit&quot; at the beginning of all bytes. That is, in TTL terms, a transition from HIGH to LOW. You just need to look out for that transition.</p>
<p>You could:</p>
<ul>
<li>Use Pin Change interrupts on 6 pins to monitor for any FALLING transistion, or</li>
<li>Use one interrupt pin with a <em>wired OR</em> of all the signals along with individual pins for each signal to determine which triggered the interrupt.</li>
</ul>
<p>To determine &quot;is it active&quot; you just need to know that an interrupt has occurred and which pin triggered it, and has that been seen within a certain time period (to be decided by you).</p>
