Query on Arduino without USB

Hi, I want to basically meddle in things I dont understand. IIRC the original Arduinos had a 9-pin nRS232 serial link. This was replaced by USB, but, for all sorts of bizarre reasons, I'd like to build an Arduino board with a serial link to the 9-pin port. I realise I would need to place an RS232 chip in between the Atmel and the pc, but, otherwise, is this not a feasible option. It may not be terribly sensible, but is it feasible? I also assume the Atmel chip would need the bootloader pre-loaded ( I have this covered )

As usual, advice and corrections most welcome. ( I wouldnt worry about a bit of abuse either )

Bruce

This emulates the original serial Arduino. It wasn't RS232, but would work with most serial PCs.

http://arduino.cc/en/Main/StandaloneAssembly

Hello Pluggy & thanks
Nice to hear from someone else in the UK.
I fear that the link you gave isnt what I’m after.
Suppose I make a breadboard Atmega328, using a 328 with a bootloader.
I should be able to send programs to it along a serial link ( to RXD and TXD ) just as you do with a standard Arduino
except that I’ll be using the 9-pin port rather than having to do it via USB
which will require a FTDI board of some kind.
The Tom Igoe board you mention only sends data out. To program it you need an AVR ISP and the 6-pin header.

I thought the original Arduinos used the 9-pin port (plus, presumably, a MAX232).
Such a set-up I should be able to bash together from my spares-box.

Bruce

Here are some simple designs that use low cost readily available transistors for voltage leveling. http://botkin.org/dale/rs232_interface.htm http://www.opencircuits.com/RS232_Dev_Board If you aren't using too much power, you can even power the AVR from the serial port.

You can get low cost and low volume parts with cheap shipping from here: http://www.taydaelectronics.com/

--- bill

Or you can use a Max232 type device. I have 328 on a breadboard that I program through the serial port. Use Uno as the board type. On my home computer I have a USB to 9 pin Serail adapter, works fine with 0.23, but doesn't with 1.0. At work I have a hardware serial port and I can program from either version.

If you are going to use a USB adapter to get the serial then might as well use something like this: http://www.ebay.com/itm/USB-2-0-to-UART-TTL-6PIN-Module-Serial-Converter-CP2102-/110908643129?pt=US_Floppy_Zip_Jaz_Drives&hash=item19d2ab9739 For only $1-2

You can use this with the IDE and then simply put a 6 pin header on the AVR target board with no interface chips or circuitry - other than a resistor and cap for Auto-reset.

It can even power the target board.

You can't use their 6 pin header directly but all the signals on the board are labeled so it is easy to wire up properly to use RTS or DTR (I recommend using RTS so you can open the port for monitoring without reseting the target).

--- bill

The link I posted will program the micro-controller, it is connected to RX & TX. It needs an ISP to put the bootloader on the chip, but thats the case anyway. The original serial Arduino didn’t have a RS232 chip of any kind, it was just a circuit involving a couple of transistors to invert the signal to and from the microcontroller. The Tom Igoe circuit just justs a 74 series chip to achieve the same thing. If you’re going to the trouble of an RS232, you might as well makes your life easier and do the full USB treatment as already suggested with the cheap Ebay adapter.

Schematic of the V2 serial Arduino. The original (V1) is officially redundant.

http://webzone.k3.mah.se/k3dacu/arduino/releases/serial_v2/arduino_rs232_v2.png

The bit at the lower left is the serial interface : 2 transistors and a handful of discreet components.

Yes you can do that. When I made a RepRap with a 662 arduino that is exactly what I did.

Thank you all for your replies. @Mike: Your post is ambiguous! Just exactly [u]what[/u] did you do? Pluggy: you're right: I couldnt understand why it would work until I read it again and also read the [u]corrections[/u]! He's got one of the 7404 gates the wrong way round. So, basically, with a level-shifter, there doesnt seem to be any reason to prevent me communicating with the AVR chip via the 9-pin port. This could be handy if I make several devices. A seperate FTDI module ( 20UKP from Sparkrite) would be a costly business. Of course, I now realise that I could get a Sparkfun FTDI module and move it about, since it plugs in. The other thing is the USB thingy /CP2102 which is a new one on me. And it is very inexpensive. Or it is in the US, but I have to see how much it would cost to get one in the UK.

Bruce

Suppose I make a breadboard Atmega328, using a 328 with a bootloader. I should be able to send programs to it along a serial link ( to RXD and TXD ) just as you do with a standard Arduino except that I'll be using the 9-pin port rather than having to do it via USB which will require a FTDI board of some kind.

That is what I did. I used a USB to RS232 cable and a level shifter on the Arduion like end. I could also have used a computer with an RS232 9 pin connector.