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Member Since: August 10, 2008

Country: United States

  • 2) The RS232 shifter board kit that I ordered from Sparkfun was slightly defective. The board failed the loopback test. The Tx LED was lighting but the Rx LED wasn’t. I used my multimeter to identify that the trace between my LED - terminal and the Rx-I connection. I fixed this by manually soldering a wire between the two connection points.

  • A couple of notes on this tutorial.
    1) The RS232 shifter board kit that I ordered from Sparkfun in September 2008 was slightly different than the one illustrated in this tutorial. You should still be able to follow the silkscreen board. Just make sure to put the diode in the spot marked 1N4148, rather than D1. Also, the silkscreen spots for the 220 ohm resistors are marked 330 ohm. I think either level of resistor will work.

  • What I discovered (eventually) is that in order for the above code to work with a 9600 bps terminal, the ATmega must be set up to operate at 16 MHz using the external oscillator. Upon re-reading this tutorial, there is a mention of using 16 MHz, but it isn’t that explicit. Be sure to configure the fuse bits to use the external clock at 16 MHz!

  • When I went through this tutorial, I initially was getting garbage data showing up on my Tera Term screen. I had been playing around with my ATmega’s oscillator settings during tutorial step 3 and had left the ATmega set up for a low operating frequency.

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