# How would I connect an HC-06 bluetooth module to an SN75176A RS-485/422 transceiver?

I am trying to fashion a small module that would allow me to connect to an RS-485 system via Bluetooth. I have found that the potentially cheapest solution would involve an HC-06 TTL Bluetooth transceiver and an SN75176A RS-485/422 driver. However, in order to prevent echo on the BT side of things, I would need to somehow detect a signal coming from the HC-06 and use it to power both the R̅E̅ and DE pins, which would otherwise be held low. The HC-06 does not provide such a pin, having only Vcc, GND, RX, and TX. How can I interconnect these two devices?

• Generally, with a microcontroller in between them – Scott Seidman Dec 5 '19 at 18:15
• Unless this can be the master it will probably not work without something to run custom software between the Bluetooth and the RS-485. If it is the master, a time based circuit for driving the transmit enable (as sometimes seen for legacy PC's) could work. You'll receive your own transmissions but software on the other end of the BT link should be written to simply ignore those. – Chris Stratton Dec 5 '19 at 18:30

How about the MAX13487E/MAX13488E. They are made for half-duplex two wire RS-485 networks and have auto direction control. The cost is $2.65 at Mouser as of 05DEC19(Compared to$9+ for the MAX3162). Which is give or take \$1.25 more than the SN75176A. The MAX13487E is slew limited(to cut down on EMI and is restricted to 500Kps) and the MAX13488E(allows up to 16Mps) is not.