Go Down

Topic: Removable programmer idea... where to post schematics, if there is interest (Read 5246 times) previous topic - next topic



I decided the other night to make a 'removable programmer' (max232 derivative based).... 

I started playing with Arduino as a breadboard with a bare chip (did eventually purchase a Uno R3).  I spent quite a bit of time (once the bootloader was loaded) wiring up a max232, debuging, swearing, etc the initial communications.  Every time I put a new chip on a bread board, I have to find one of my other bread boards for referance, make all the connections, swear because I missed something etc, rather than just getting to work on the project.

Anyway, my idea was:  Since Reset, TX and RX are all at the edge of the chip, put a +5 and GND in the rows to the left of the atmega chip, insert a 5 pin header in, and put a removable serial programmer so I wouldn't have to re-wire the max232 every time.  Also, with the AtMega chip and the max232 and a reset button, about 1/2 the board is used up.

I also added a reset button (with the pull up resistor) to the little board (14 row of a perf board) since I was connected to the reset pin anyway.

Next version (though of this as I was finishing up) will have an extra pin to connect to the next digital pin beside TX/RX (chip pin 4 digital pin 2), that can be jumpered/switched hi/lo for serial debug enable/disable via code (and if the board isn't there, debug would be disabled)...

anyway, after all of the above blathering, where would the right location be to post a write up/schematics?




Aren't you kind of re-inventing the wheel here?  How does your contraption differ from a standard FTDI cable, the USB BUB offered by Modern Device (http://shop.moderndevice.com/products/usb-bub), the FTDI Friend offered by Adafruit(http://www.adafruit.com/products/284), the FTDI Basic Breakout offered by Sparkfun(http://www.sparkfun.com/products/10008), etc.



Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)


Okay folks - If the idea were to never try anything that might already be available from somebody else then why do we have some many clones of the basic Arduino?

Post your Idea here and it might turn out that you have a different/cheaper/simpler/quirkier/more useful/less useful idea that others can look at, and make suggestions over so that you and others can have the chance to learn and develop the art of hardware and software.


@xferboy, I made a pair of small boards that may be somewhat similar to your idea, except that I use the Adafruit or Sparkfun FTDI boards instead of a MAX232. There is a write-up here if you're interested.



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:
1) 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.
2) can be made for ~$5 to $7 based on what you may or may not have in stock already
3) you can learn a bit
4) some devices may only work with 232.  Ok this is a bit of a stretch, but....
5) 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:

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  http://avrprogrammers.com/bld-sardp2.php  (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


(hope these links work, first time I've done this)


Looks good.

Might try doing something similar that has the 2 power pins plug right into the breadboard power & ground.

Go Up