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[Reply #15 on:]

By crap design, do you mean something like this?

Yes that is quite a crap design. There is no negative voltage generator. It won't work with a real RS232 interface but will probbly work with the crap ones you get on PCs.

is it possible that the onboard arduino UNO serial to USB chip is interfering with data being received from the max232 chip that is sitting between the RFID receiver and the arduino UNO.

Not likely if the USB is not receiving anything. There is a 1K series resistor between the arduino and the USB chip so a direct connection from a MAX232 will be able to over ride it.
However the fact that you have built it twice and got different results suggest you are not building it right. Also as well as the baud rate have you checked the parity?

[Reply #16 on:]

By crap design, do you mean something like this?
Yes that is quite a crap design. There is no negative voltage generator. It won't work with a real RS232 interface but will probbly work with the crap ones you get on PCs.

Crap!  Thanks for the tip, Grumpy_Mike.  I am reading the output from a digital scale using an RS232 shield from CuteDigi.  This shield works great and also allows me to send commands to the scale (like tare, print, etc.), but I can't upload programs while the shield is installed.  Another crap design?  Now that I've mastered discovered SoftwareSerial, I want to replace the shield with a simple adapter.  Do you think what I ordered will work?  I guess I'll find out soon enough...