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Forum Index : Microcontroller and PC projects : Pin 7 Com1 enable

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Herry

Senior Member

Joined: 31/05/2014
Location: Australia
Posts: 261
Posted: 03:40pm 26 Mar 2016
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I'm puzzled about the purpose of this pin. I am reading from a GPS module into the MM using pin 22 (Com1 RX). I have the program line set as OPEN COM1:9600 AS #1 and I am reading from GPRMC, parsing the stream. This all works so what is the purpose of Com1 enable?
Edited by Herry 2016-03-28
Senior?!  Whatever it says, I'm a complete and utter beginner...
 
Zonker

Guru

Joined: 18/08/2012
Location: United States
Posts: 767
Posted: 05:57pm 26 Mar 2016
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Hey Herry...

The Com 1 EN pin is used to control an Rs-485 Transceiver IC... This IC allows for serial com using 3 (or 2 and GND) wires, but is different the Rs-232 in that the two wires form a half duplex type for data transfer between 2 or up to 256 "nodes"...

The wires use a differential type transmit/receive system inside, and as such, can carry the serial data stream a very long distance between each "node" if needed.

Since the same set of wires is used to transmit AND receive data, a pin from the Micromite is needed to control the IC's Tx-Rx functions. Then, whan you want to send a massage, or "packet" of data to the other nodes, the Micromite automatically controls the IC's control pins for you...

Look in the Micromite manual on page 82 "IEEE-485" to read about it. I helped Geoff test this subsystem, as I needed it for a project, and I am glad he included it into the MM firmware.. I have used it several times and it works like a champ..!

Hope this helps..! Edited by Zonker 2016-03-28
 
Herry

Senior Member

Joined: 31/05/2014
Location: Australia
Posts: 261
Posted: 06:02pm 26 Mar 2016
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Thanks. So not applicable to my program, I suppose.
Senior?!  Whatever it says, I'm a complete and utter beginner...
 
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