Connect MAX485 to PIC16F690?

ThomasC · Joined: 09 Oct 2007 Posts: 62

PCM 4.060

I have used this link:

MAX485 to PIC16F877
http://www.ccsinfo.com/forum/viewtopic.php?t=25720&highlight=rs485

and from Humberto's post I used this:

RO -RC7
DI -RC6
-RE/DE -RC5
pin5-GND
pin8-VCC

and derived this for the PIC16F690

MAX485-----------PIC16F690
1 R0------------RB5-RX
4 DI------------RB7-TX
2/3 RE/DE--------RC1-Pin Assigned for directional control
5 PIN 5---------PIN 20-VSS
8 PIN 8---------PIN 1-VDD

Did I do it correctly? Thanks everyone!

treitmey · Joined: 23 Jan 2004 Posts: 1094 Location: Appleton,WI USA

ThomasC · Joined: 09 Oct 2007 Posts: 62

Do I need caps on the pins like the MAX232?

Which pins of the MAX485 do I use to hook up to the RS485 connector?

My telebyte Model 245 opto-isolated superverter needs a T-/R- and a T+/R+.

I do notice that I have an Inverting Driver Output, Inverting Receiver Input and Inverting Driver Output, Inverting Receiver Input,and a NonInverting Receiver input and Noninverting Driver Output.

I'm thinking of using PINS 6 (Noninverting Receiver Input and Noninverting Driver output) and 7 (Inverting Receiver Input and Inverting Driver Output).

Thanks again.

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

The MAX485 does not need any voltage boosting caps. Pins 6 & 7 are the standard 485 lines A & B. A probably connects to T+/R+, and B to T-/R-, but reading the Telebyte should tell you for sure.
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ThomasC · Joined: 09 Oct 2007 Posts: 62

Thanks. I hope I've gotten proficient enough where you guys are just nudging me instead of holding my hand through this. Razz

ThomasC · Joined: 09 Oct 2007 Posts: 62

quick question. Can I leave my PIC16F690 plugged into the MAX232 and its serial connector while I have the MAX485 plugged in? The MAX232 is not hooked up to the PC's serial port or anything else.

Humberto · Posted: Wed Jan 23, 2008 8:18 pm

Ken Johnson · Joined: 23 Mar 2006 Posts: 197 Location: Lewisburg, WV

Can I leave my PIC16F690 plugged into the MAX232 and its serial connector while I have the MAX485 plugged in?

I haven't looked at these particular parts, but I'm pretty sure . . .

They'll both be driving your pic rx line when the 485 receive enable is assertted (low).

I've done this using an and-gate - when either signal goes low, the pic rx then goes low. Probably also need a pull-up between the 485 output and the and-gate, 'cause when the 485 rx is disabled, the output is hi-impedance (methinks)

Hope this is helpful Smile

Ken