The Devantech USB to RS485 module provides a complete bridging interface between USB (type-B) and RS485 signals with a simple Virtual COM port software interface. It makes use of the ST485 chip which features reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables. The modules may require installing FTDI's virtual COM port drivers for your operating system.
This adapter features automatic direction turnaround. Under idle conditions, when no data is being transmitted or received, the adapter will be in the high impedance listening mode. Any data that arrives on the RS485 bus will be transmitted via the USB port to the PC. When the PC transmits data, the bus direction immediately "turns around" to transmit the data out on the RS485 bus. There is a 3µs delay after the end of a transmit packet to ensure the final data high bit is received before setting the bus to idle (listening) mode again.
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