Using the tx rx pins on Arduino Duemilanove

I'm just beginning with a Arduino. I would like to connect it to a shiny new vdip2 that I also purchased. However the first thing I need to do is use the tx and rx lines to communicate to the vdip2.

Just trying to verify that I can hook up the tx rx and ground pins and get something useful out of it. I have loaded the 'ASCII Table' sketch up to the Arduino using the usb line. I have confirmed that I can turn on the serial monitor and receive the ascii table off the usb line.

Next I disconnect the usb line reset the Arduino and then connect up a serial line to a winblows laptop with a serial monitor on com1. I have used schematics on-line to create a female DB-9 connector with hookup wires attached to the pins:

#5 ground
#3 tx
#2 rx

I've inserted these hookup wires into the 0 and 1 pin on the Arduino:

#5 ground -> arduino ground pin
#3 tx -> arduino #0 (rx)
#2 rx -> arduino #1 (tx)

I press the reset button on the board and then through the serial monitor on the windows box, I see that there is output, however it's not an ascii table. It's a bunch of garbage. I have set the serial monitor to 9600 8 bit no parity

My goal is to write a simple data logger app that will take temperature readings from an LM34C Fahrenheit Temperature sensor and log readings to a USB memory stick. Heck that part was about 5 minutes of work... this part is taking much longer!

If I understand the VDIP2 specs correctly, I will need to listen on the serial pins for "[ch65279][ch65279][ch65279][ch65279]Ver·xx.xxVcccF·On-Line:" Then send it commands to open a new file and start dumping temperature readings to the file.

Any help or suggestions would be greatly appreciated.

Sounds like you have physically hooked it up, but the Arduino serial port is TTL level serial, whereas your PC is RS232 level serial. You need a level shifter, the classic part is the MAX232.

Ok first lesson under my belt. There's a difference between rs232 and TTL serial.

I have since then purchased a DLP-TxRx-G USB to serial adapter. I have confirmed that the DLP-TxRx-G works with the Arduino. I loaded the ASCII table on to the Arduino, and then hooked up the TxRx to it and I can confirm that I receive the ASCII table through it on the USB line.

However using the DLP-TxRx-G, I still can't get the vdip2 to connect and go into monitor mode. I still just get it blinking between the two leds. I guess this is no longer an arduino issue and is now a vdip2 issue... Any suggestions would be appreciated.

Any chance I could have fried the vdip2 if I tried to use RS232 serial on it? Geeze, I hope not. :cry:

Any chance I could have fried the vdip2 if I tried to use RS232 serial on it? Geeze, I hope not. :cry:

Yeah, that definitely could fry something. RS232 could be 15-30V and swings AC. Needless to say a TTL (rated 0 to 5v) device is not rated to have 30V negative on an input pin. Nor is it rated to have 30V positive on a pin. Your RS232 serial might only have been 15V but that's still three times the rated voltage of a 5V TTL device.

Any chance I could have fried the vdip2 if I tried to use RS232 serial on it? Geeze, I hope not.

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Normally applying a RS-232 level voltage (which can vary between +/- 3vdc to +/- 15v) can cause damage. However if the the voltage source is current limited then even though the negative or positive voltage were enough to cause the input protection clamping diodes to conduct, there may be no permanent damage due to the current limit set by the RS-232 output drivers. So if your vdip2 has internal clamping protection diodes like the Arduino does,you might have dodged a bullet on this one. :wink:

Lefty

would it be possible to program a pro mini or lilipad with the rx tx of the duemilanove(which is hooked to pc with usb), or is a ftdi breakout-board necessarily required?
thanks.

would it be possible to program a pro mini or lilipad with the rx tx of the duemilanove(which is hooked to pc with usb), or is a ftdi breakout-board necessarily required

Yep just pop out the AVR in the duemilanove and connect the rx's, tx's, and ground.