serial pin 0 and 1

Ok. I'm making an IR receiver with my arduino to be connected to a computer via the serial port only. I don't want to use USB and I'm going to power the arduino with a dc power adapter (or with a power connector from the psu on the computer). I need to connect pins 2 and 3 from the serial port on my computer to 0 and 1 on the arduino correct?

I coded it using USB and vb.net on the computer. The computer sends a number "3" (arbitrary ready command) to the serial port (COM3 when I programmed it with USB) and the arduino reads the "3" and turns on an LED on pin 8 to show it's ready. The arduino exits the "waiting-for-ready-signal-from-computer" loop. Now the arduino simply sends whatever IR commands it receives as corresponding text phrases ("PAUSE", "NEXT", "PREV".. basically a music control system) via serial to the vb.net program. Simple enough and it works great with USB. The vb program performs functions based on what text it gets from the arduino.

I can't get it to work with pins 0 and 1. I disconnect the unit from usb, plug in the external power supply and change the port to COM1 in my vb.net program. Is that all I need to do? As far as the arduino code is concerned serial is serial right?

RS232 is not the same as the serial on the avr

for one its a different level of voltage, typically +12 and -12 volts , which should have blown your arduino off the board. But most computers today half ass it with a 0-5 volt signal so you may be lucky

next its inverted so high = 0 low = 1

so you need a level shifter and inverter, you can buy one or make your own, here is a simple one but its not great for high speeds

http://wiringschematic.net/simple-ttl-rs232-level-converter-using-transistor/

or another I personally use (both fairly easy to build and cheap to buy)

Osgeld:
or another I personally use (both fairly easy to build and cheap to buy)

http://cdn.shopify.com/s/files/1/0038/9582/files/P34Man.pdf?1262632031

Ok I bought this serial adapter and assembled it and it transfers sketches to my arduino just fine. However, when I send a message via COM1 to my arduino in VB.net it doesn't seem to receive it or maybe it doesn't understand it. I get no errors, the port opens ok and all. And it all worked just fine via USB. Is there something special I have to do in VB.net when I send the strings?

http://img443.imageshack.us/img443/2699/imag0468.png

Anyone?

brianhj:
Is there something special I have to do in VB.net when I send the strings?

Strings? Serial doesn't transmit strings. It transmits bytes, one at a time.

So let's look at how your Arduino code receives "strings."

Osgeld:
or another I personally use (both fairly easy to build and cheap to buy)

http://cdn.shopify.com/s/files/1/0038/9582/files/P34Man.pdf?1262632031

I'm surprised that works at all, because looking at the schematic, it doesn't generate anything like the correct RS232 voltage levels. Something based on the MAX232 chip is much more likely to work. Search for MAX232 on ebay to see what's available.

it doesnt have to for most modern computers