RS485 transceiver for UART in Half Duplex (single wire mode)

[cpinkstone2]

Posted on June 11, 2012 at 10:32

Hi,

Can anyone recommend an RS485 transceiver that can be used with a STM32 UART in half duplex (one wire mode) ?  I've considered an ST3485E but would need extra GPIO lines and software to drive the receiver and driver output enable lines on the transceiver. Does a simpler device exist?  Thanks.    #uart-rs485-single-wire-stm32

[ColdWeather]

Posted on June 11, 2012 at 12:10

Does a simpler device exist?

AFAIK - not. Depending on the requirements to the bus, you could apply two hardware solutions: 1). You ground the TX input of the tranceiver and connect the CPU TX via an invertor to the DE input: while sending, the driver part of the tranceiver will switch between 3-state (high impedance) and active. That does not correspond the specification of RS485, but if your bus is not too long and you terminate it once by a 330R pull-up to D+ and 330R pull-down to  D- and 330R between D+ and D- to set the definite state to the bus while all attached tranceivers are off, it will work fine. The RE input to be grounded, too. The software must be ready to receive/ignore the echo of the own data when sending.

2). You can use a

http://www.interfacebus.com/CAN-Bus-Description-Vendors-Canbus-Protocol.html#a

-Tranceiver like SN65HVD230 from TI or any similar from other EM.

[alok472]

Posted on June 11, 2012 at 12:21

Using ST3485E is best...Using additional IO is not complex and debugging is very easy.