Half duplex transceiver signal (active low) sync

Most half duplex transceivers, be it RS485, CAN, UART, or other, will work based on pure logical signals. This means when data is sent through the TX, it automatically loops back through the RX pin. Usually this is up to the device sending data to filter out. The signal coordinator does exactly that, when the TX is activated, the RX is automatically muted on the signal by signal basis, independently of the protocol. This specific model only works for signals that are idle high and active low.

The main useful cases

There are a few but rare isolator devices for the several protocols, usually quite expensive too. Lets say, there is a need to have a fully isolation point between two off-the-shelf devices that communicate through CAN. The simple solution, is to pay out large sums to buy an isolator. The cheap solution, and now fast thanks to this device, is to make a quick design with 2 back to back CAN transceivers, being one of them fully isolated, and place this device coordinating the TXs to RXs signals of both devices (as per the image bellow). Creating this way a cheap and effective fully isolation CAN to CAN device. (Or RS485, UART or other). (Valid for other transceivers that are half duplex to TX/RX signals, low side activated.)

Abilities and limitations

Large voltage range, 3.3V to 12V (for best results, 5V)

Full signal integrity (80%+) in speeds up to 1Mbit. Only supports signals that are idle high level and active low level. Only supports direct Push/Pull or open drain output drivers with at least 2.5mA per volt driving ability. High impedance output drivers will work badly or not at all. (For example, our half duplex to full duplex converter will only work at a maximum of 5V when both TX and RX protection resistors have been replaced with 0ohm).

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