Two MicroControllers

[Pommie]

This could be done just using the hardware UART. By using a diode AND gate you can have two slave processors outputting to one master.

I.E.
**broken link removed**

TX3 can connect directly to RX1 and RX2. Processor 3 would then request data from the 2 slave processors.

Mike.

 

[Eng.Remon]

i think of using max232 wid rs232 is dat would be good?
but i need some help to understand how the serial mode is working on transmitter and reciever?

 

[Nigel Goodwin]

i think of using max232 wid rs232 is dat would be good?
but i need some help to understand how the serial mode is working on transmitter and reciever?

My RS232 PIC tutorial explains it, you don't need MAX232's if you're just talking from micro-controler to micro-controller.

 

[Eng.Remon]

what about the voltage converstion!? 3<->5

 

[Nigel Goodwin]

what about the voltage converstion!? 3<->5

Was it ever mentioned that it was two different voltages?.

 

[Eng.Remon]

yea what i got from a reference that the uc works on ttl vorltage 5 v and the Rs232 works on 3 volt so the max232 is used to make this convergence
isnt that right ?!

 

[Nigel Goodwin]

No it's not - TTL is 0-5V, RS232 is -12V to +12V.

If you're going from PIC to PIC you just need to connect the 5V levels.

 

[3v0]

Recap.

To send or receive serial data you need a UART.

The UART can be either hardware or software.

If it is hardware it can be built in to the microcontroller, or it can be an external chip.

If it is software, it is code that runs on the microcontroller, aka bit-bang code.

The UART logic level is that used by the processor, most often 0V and 5V. At least 3 wires are needed at each UART. RX, TX and a GND. This is all that is needed with no flow control or software flow control

To get the signal to travel further then possible with 0V and 5V you can use an RS232 level shifter. It converts the 0V/5V to +12V/-12V.

HTH

 

[Nigel Goodwin]

At least 3 wires are needed at each UART. RX, TX and a GND.

I don't like to complicate matters but this isn't strictly true, with micro-controllers, and a software UART, you can do it with just ground and a single I/O pin, a combined tx/rx - switched between tx and rx in the software. Obviously, unless you're short of pins, it makes more sense to use seperate ones - but it's perfectly capable with just the one I/O pin if needed.

 

[3v0]

I don't like to complicate matters but this isn't strictly true, with micro-controllers, and a software UART, you can do it with just ground and a single I/O pin, a combined tx/rx - switched between tx and rx in the software. Obviously, unless you're short of pins, it makes more sense to use seperate ones - but it's perfectly capable with just the one I/O pin if needed.

I know that, you know that, and the OP is having difficulty getting his head around basic concepts...

 

[Eng.Remon]

oh, thnx 3v0 but i dont think u know everything Right!!. at least i m trying to learn. thnx All who Cares

 

[3v0]

I am sorry if you feel insulted.

Whatever...

 

[Eng.Remon]

no problem.
Whatever...

 

[3v0]

There are many ways to to what you want to do. What I was attempting to do was to keep it straight forward so you could get where you were going with the least difficulty.

Many of us here have years of experiance and could provide you with many ways doing this. That would be confusing to most anyone attemping to get his/her head around the basics.