Standalone - how to interface?

Hi there…
I am about to start my first ‘stand alone’ Arduino “project” and wanted to know if it is possible to attach the arduino simply to a RS232 Port with its TX and RX ports to send data to it through an USB/Serial cable

Also, would it be doable to get enough power from a serial cable to power the Arduino and maybe a small LCD Display?

Instead of RS232, could you use USB?

  • Brian

i would like to not use the prolific usb/com or ftdi usb/com chip as i am unable to solder smd… so (afaik) usb is a nogo for me - except if there was something like our FTDI chip on DIL… also i would like to have it as cheap as possible

Are you looking for a long-term serial connection to the computer, or just short term for programming / debugging?

programming would be a bonus - but most important would be sending and receiving data.

Easiest would be to buy one of these - http://www.adafruit.com/index.php?main_page=product_info&cPath=33&products_id=70 - it has a USB converter chip built into the cable.

Then on your standalone project you just need to provide (at minimum) a 3-pin male header - GND, rx (pin 0) and tx (pin 1).

If your atmega has the bootloader this is all you need for both programming and communications.

i would like to not use the prolific usb/com or ftdi usb/com chip as i am unable to solder smd

You misunderstood my question. Let me try again… Is there a reason you want RS232? Will you be connecting to a device that only supports RS232? Or, do you need a way to transfer data between the microprocessor and a host computer?

  • Brian

ok, i got the question wrong - yes, its simply to connect the hardware with a pc but i figured out it would be quite hard to solder a com/usb chip by myself so i gave up thinking about usb in the beginning… but that idea with using a usb/serial cable sounds very interestering, especially since i have a bunch of them littering arround here…

Yes there’s nothing wrong in doing this. The only down side is the voltage translation as the RS232 levels are not what the Arduino wants. You can do it properly with a driver like the MAX232 or use a couple of transistors.
Make sure you bring out (and convert) the control line to do the auto reset bit.

the max232 variant looks nice for me… are there any schematics available how to solder it to the arduino? Or is it as simple as taking out the datasheet and connecting RX->RX TX->TX CTL->Reset etc?

Or is it as simple as taking out the datasheet and connecting RX->RX TX->TX CTL->Reset etc?

It is but check that what they call TX & RX is what you think they are. The term TX & RX can get a bit confusing because it changes acording to if the equipment is classed as CTE or DTE see http://en.wikipedia.org/wiki/Data_terminal_equipment

Just make sure you connect the output from the MAX to the input of the Arduino and output from the Arduino to the input to the MAX

its simply to connect the hardware with a pc

In that case, these worked well for me…

http://www.pjrc.com/teensy/index.html
http://www.pjrc.com/teensy/teensyduino.html

You can fit several small wires into the solder-pad-holes. The 5V from the USB connection is available on the board. Communications is just like the Arduino (a serial port on the PC side, the Serial object on the microprocessor side).

Good luck,
Brian

There’s a really great tutorial on stand alone arduinos here:

http://www.imagearts.ryerson.ca/sdaniels/physcomp/tutorials/Arduino_standalone/ard_hack.html

And a specific page about serial connections here:

http://www.imagearts.ryerson.ca/sdaniels/physcomp/tutorials/arduino_serial/ard_serial.html

He’s not using a MAX chip I don’t think, it looks like a different one, but connections to the atmega should be the same.

that tutorial on stand alone arduinos is just perfect, thanks :0)