[Ask] PPI8255 or Serial?

[Tumpal H.S]

hallo...

As a newbie i want to ask about the easiest or better way to establish communication between mainboard PC with Microcontroller?using PPI8255 or Serial?

and if you don't mind can you explain it tu me?

Thx.....

 

[Diver300]

Use serial. It uses a lot less wires.

PCs usually have RS232 ports. You need a MAX232 or similar to convert voltage levels from the +/-12V of RS232 to 0 - 5 of a microcontroller.

Chose a microcontroller with a EUSART.

You can use a terminal emulator to send what you type to the serial port, and put on screen what arrives from the serial port.

 

[Nigel Goodwin]

And why would you want to use an antique 8255 anyway?, micro-controllers are far better ports to start with.

 

[Tumpal H.S]

But if i want to use 2 microcontrollers ( DT-AVR 8535 ) and RS232 port from PC, what device should added between them ( mainboard PC can communicate with 2 mircocontrollers separately ) ?
And what are the different between RS232 and RS485? advantage and disadvantege between them?

 

[Nigel Goodwin]

Use a MAX232 or similar, or (with a PIC, and using a software UART) you can use just a single resistor.

It's really extremely easy to do RS232, in either hardware or software - there are PIC examples in my tutorials.

 

[CCD]

But if i want to use 2 microcontrollers ( DT-AVR 8535 ) and RS232 port from PC, what device should added between them ( mainboard PC can communicate with 2 mircocontrollers separately ) ?
And what are the different between RS232 and RS485? advantage and disadvantege between them?

If u use MAX232 or compatible, it has two RS232 tranceivers on single chip. So, two microcontrollers can communicate with pc, both at a time if you use two different ports on pc.

RS232 signals are +15, -15 referenced to ground, while RS485 signals are differential. Also, RS485 is multipoint communication where many devices can be connected on a single RS485 bus. the problem is, PCs don't have RS485 port,so u need a RS485/RS232 converter!!

-----------
AVR projects:
Design with Microcontrollers

 

[Tumpal H.S]

@Nigel Goodwin

my adviser told me to find out about serial and PPI8255, i don't really know if PPI 8255 is antique.....

@All

So can i say to make my PC board ( with only 1 serial port ) can communicate with 2 µcontrollers separately ( multipoint communication ), it's better to use RS485/RS232 converter ( PC board -> RS485/RS232 -> 2 µcontrollers ) ?

 

[CCD]

Max3162 can do the job. it's an RS232-RS485 protocol translator. the RS232 side u can use for connecting with PC and both your controllers can be connected on RS485 line.
refer to this application note from maxim:
**broken link removed**

And here is a simple RS232/485 converter using the max232 & max485:
**broken link removed**

for starting on RS485, u can refer to this application note on RS422/485 bus:
**broken link removed**

--------------
Design with Microcontrollers

 

[Tumpal H.S]

@nigel

can you explain to me why PPI 8255 is an antique?

@All

Can you explain to me what are disadvantage n advantage using 8255?can 8255 do multidrop communication?