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Topic: Arduino Standalone + rs232? (Read 1 time) previous topic - next topic


Hello All Arduino-ers,

I am trying to program my Arduino Standalone(http://arduino.cc/en/Main/StandaloneAssembly) through rs232, how do I do this (treat me as being as nooby as my username would suggest in your explanations)



There is a simple solution for this: Buy a USB-to-TTL-serial-adapter from Ebay. Connect it to RX and TX.
Or use an Arduino with a serial adapter included.


I have a USB-rs232 connector already.


Is it TTL-level, or a higher voltage RS-232 level signals ?


I'm not sure, I bought it on Amazon, here is all the info on it.

USB to Serial RS-232 DB9 Adapter Cable

Product Features
     Converts a USB port into a 9-pin male RS-232 serial port
     Powered by USB port
     Supports Windows 98/2000/Me/ XP, Mac OS(8.6/9.0)

Technical Details
     Brand Name: DekCell
     Model: undefined
     Item Package Quantity: 1

Heres a link: http://www.amazon.com/gp/product/B000BI95W0/ref=pd_rate_rs


I see.
It is easier to have a adapter from USB directly to TTL-level serial lines.
The old RS-232 uses higher voltages.

Adafruit has both of them, with some explanation:
(1) http://www.adafruit.com/products/18
(2) http://www.adafruit.com/products/70

If you did build that stand-alone, the 7404 is probably used to be able to handle that higher voltage.
I hope you read the comments for this schematic: http://arduino.cc/en/Main/StandaloneAssembly
The RXD is an input, so the 7404 port for RXD is drawn the other way around. Also the /RESET is wrong and there are more problems. So the schematic is a total mess.

Perhaps it's better to start all over again.
Do you have a bootloader programmed ?
Can you upload your schematic (and a photo) ?

Did you already use a normal Arduino ? Building one yourself is easier if you already have used one.


T`hank you for all you have said so far,

I've built my circuit on a breadboard and it works, the Arduino and everything, if I program the Arduino through the Arduino Uno board.  All that happens when I plug it into my computer is it says it cannot install the driver software(I have the software necessary to use the Arduino Uno).

Picture-wise it looks just like the one from the link I gave.

Could you elaborate on the problems in the circuit from the link?


That cable wants to put out ~+/-10V signals on the Tx line that would connect to your Rx, and expects your Tx pin to output +/-10V signals.
The ATMega328 on the  board only handles 0/5V signals. Higher than 5.5 and lower than -0.5 will damage the IO pins.

If you're on a breadboard, then add a MAX232 type chip to handle the signal level conversion.
Need 5 0.1uF caps to create the +/-10V signal outputs that the cable needs.

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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