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October 5, 2009
Tutorial - TX and RX Signals
about 4 years ago
Like somequy7234 said, UART specs says idle status of an tx line must be logic high. Also a tranmitted bit would be logic low on the line. <br />
If we connect multiple devices tx lines together and if one wants to transmit data using tx line of itself, other slaves tx lines doesn’t allow masters rx line to be pulled low. <br />
So by placing reverse diodes like that we only allow logic low signals to be passed to the masters rx line. That would be the sending slave. <br />
Also i would like to note, there is no way multiple slaves could talk at the same time in this configuration (same as all other busses).<br />
Hope i could explain how and why it works.
This is great tutorial but there is a way to connect multiple UART receiving/transmitting devices on the same bus. <br />
Master’s transmit line connects to all receivers rx line as usual. <br />
Each Slaves' transmit line connects to a reverse diode -diode’s negative pin to slaves tx- and positive end of the diode to bus<br />
example circuit<br />
I have been using this circuit for a long time. Also i am designing a BMS which includes something like this.
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