Morning,
I don't consider this re-inventing the wheel, more taking an existing design and re-purposing it for my requirements. (Roller skates, bikes, cars, semi's, farm tractors, large dump trucks all have wheels, but they're all different)
I don't mind purchasing finished products, but I do like building from scratch the first time. I find I learn more, and understand the parts that make the whole product better. I did build my first *duino with a bare chip, wired it for power, crystal, comm, etc, burned a boot loader, and then used it. After that, I went an purchased a Uno.
A few pro's I see from this:
- it will save space on a breadboard that is short on space. All that is required is 2 extra rows. By using one of the FTDI cables, it looks like you need 5 rows since you can't line up the ones I looked at. 8 rows if you want a reset.
- can be made for ~$5 to $7 based on what you may or may not have in stock already
- you can learn a bit
- some devices may only work with 232. Ok this is a bit of a stretch, but....
- if you build a project that doesn't always need comm, this can be put back on if comm is required (debug, re-programming, etc)
Anyway, after that little rant, here's some of the details:
Parts:
14 rows of perf board (breadboard style) - only had to split one row for the LED's
st232cn (mostly identical to one of the max232)
5 1k or so resisters
5 .1uF caps
1 100uF cap (folded under for support as well)
2 LED's
some wire
db9 female
2x5 pin header (1 row would work, but dual gives a little more stability)
some random wire
a push button switch
I use higher value R's (1k vs 330) for the LED to save a little power
I started with the following circuit avrprogrammers.com - (big thanks)
. I didn't use the 4-6 and 7-8 wiring.
-added a 1K resister between the RX, TX and the AtMega (I've done this on previous breadboarded version)
-swore when it didn't work (left it for the evening)
-realized the next day that eventually RX has to become TX and visa versa, (TX from the chip was sitting at ~1.8v, output-high to output-low fighting) changed the circuit and it worked.
-added the pull up resistor and switch to gnd on the reset.
end result
I think that's it. If anyone wants more info, let me know
Allan
(hope these links work, first time I've done this)