PIC and MAX232 in/out

[The Master]

Hi. I made some circuits a while ago that take commands from a PC through serial. The circuits could also send out serial to each other. Since then ive been told i really shouldnt be using the method i was using and i have to put a MAX232 chip (or similar) between the PICs and the PC.

I have 3 wires. DataIn, DataOut and Common. When the PC is sending the commands this isnt a problem. PC > MAX232 > PIC. I know how to do that much. The problem comes when the PC isnt around and one of the PICs wants to send commands. How do i go about doing that?

Before i simply used the seriout command on the same pin that usually used serin. This time i will be using hardware UART so i can do PWM and a MAX232 chip. Both of those things stop me from sending data out of the DataIn wire.

I had a thought. Can i use a seperate pin on the PICs so when its set as the master it uses serout on some other random pin which makes use of the second output of MAX232. Connect the output of the MAX232 into the input (the DataIn wire). The master chip will ignore itself and the others will listen.

Is this possible? Is it the best way? Will it work without something exploding? lol

[mackrackit]

If you have the in line resistor between the PIC and PC the MAX chip is not needed. The MAX chips are for inverting signal levels and adding some boost to the transmission..

If you were using USART then yes you need it, but then it would not work with out one.

So, the software SERIN/SERIN2 is OK straight to the PC if the distance is short enough.

[The Master]

I plan to use these circuits in my disco lights. Im using 3 pin DMX cables but the last light could be a total of 30-40 meters of wire away from the PC.

Im using the serial RX/TX pins on the pic chip. Last time i tried that i was told its impossible without a MAX232 chip. When in slave mode the chips wont be using serin. It will use the other code which i cant remember off the top of my head but it reads bytes straight from the buffer.

As far as i know i would need a 3rd pin for one of them to act as a master. When acting as a master a normal serout should work fine but its how to connect that pin into the DataIn wire so all theo ther lights pick it up

[mister_e]

Usually DMX will use something like a 75176. Open the datasheet, and see how you could trick it.

But MAX232 is really not what you need to use to meet the real DMX protocol/requirement.

[The Master]

Sorry if i wasnt clear. Im just using DMX wires. The actual circuits will use RS232

[mister_e]

Depending your baudrate and if you need interrupt, SERIN/DEBUG/SERIN2 may have their advantages.

HSERIN's timeout could be handy in this case. You send data, next line is a HSERIN if the timeout happen, you do something else.

Maybe i need another coffee