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1  Using Arduino / LEDs and Multiplexing / LED sink drivers, daisy chained to a shift register... on: September 10, 2012, 08:48:31 pm
Hi. I'm building a common anode LED cube. Seems to be a popular project, and great soldering practice for my son!

I found this excellent project, where daisy chained STP16CP05 (constant current sink drivers) are used to sink the cathode columns and the last one in the chain is used to switch some transistors that source the anode layers.
Full project:

He built a great project and was kind enough to make an excellent tutorial. However, I'm not sure how to use a constant current/ voltage-varying device like the STP16CP05 to switch a MOSFET. It seems like voltage (from STP16CP05 output) to the MOSFET gate would be varying while the MOSFET gate charges, since the STP16CP05 is a constant current device. His design certainly works, but I'm interested in learning rather than just copying a design.

So my question is, if I were to replace the last device in this chain (to switch the MOSFETs that source the anode layers), should I connect my last STP16CP05 to a latching shift register? For example, it looks like I can daisy chain a 74HC595 shift register to the end of the STP16CP05 chain. Output of the 74HC595 is only 35mW max, but I assume that would be enough to drive some MOSFETs like IRF7424 or IRF9328.

Does this sound like a good solution, or am I just complicating the design? I could just use another STP16CP05 as in the project at the link above. I already have enough STP16CP05 to do that, and I could use those to drive the MOSFETs if that is just as good. I would appreciate any advice.
2  Community / Local Groups / Any Arduino kids in Evanston, North Shore, Chicago area? on: July 24, 2012, 02:46:16 pm
Hi. My son is a 5th grader and would love to find another kid who is into Arduino, raspberry pi, electronics projects. He has been building fun stuff. Please get in touch if you're in the area mjanse a gmail dot com.
3  Using Arduino / Interfacing w/ Software on the Computer / Re: SOLVED:Sketches to breadboard-arduino..without removing the real Arduino's chip? on: April 21, 2012, 11:52:46 am
Doh. And here's another set of instructions that is probably better. Just found this.
4  Using Arduino / Interfacing w/ Software on the Computer / Re: Sketches to breadboard-arduino...without removing the real Arduino's chip? on: April 21, 2012, 11:22:54 am
Update: I did find a way to do this some time back, and am posting to help someone else. The only issue is that downloading the sketch in this manner programs BOTH ATMEGA, meaning the one in the real Arduino board and the breadboard. Not an issue but you need to know that you'll lose the Arduino ISP sketch on the real Arduino so just have to re-download it.

Attach the breadboard arduino to the real arduino as here using the "Burning the Bootloader" configuration NOT the picture below, which shows how to do it IF you remove the ATMEGA from the Arduino (which I was trying to avoid):

Also, in this configuration, you need to connect a 120 ohm resistor from reset to 5V on the Duemilanove/real Arduino board.

Then, in windows, open a DOS command window and go to the directory that has avrdude in it (you have to enter this line while in that directory, I believe). I won't go into all that here since it can be googled. The following command worked for me, where "three.hex" was the compiled Arduino code that was found in a temp folder (you can search for how to find the compiled code).

avrdude -F -p m328p -c arduino -P com3 -b 19200 -u -v  -Uflash:w:three.hex

Last hints: make sure you didn't erase Arduino ISP from a previous attempt. Reload it if needed. Remember the 120 ohm resistor on the main board. Use the avrdude command that ignores the chip identification code from the breadboard ATMEGA (if it isn't in the line above), Mess with baud rate if needed. I believe some had success with higher rate.

If someone gets this to work, please post more details for the community. I may have forgotten something but above is what I had in my final notes.
5  Using Arduino / Interfacing w/ Software on the Computer / Re: Sketches to breadboard-arduino...without removing the real Arduino's chip? on: February 18, 2012, 09:18:05 pm
Thanks, but per that link and others I've researched, to burn the bootloader one can leave the chip in the Duemilanove board. I did that. It worked. However, to upload sketches, that's not the case (see quote below).

So what I'm asking is how to use an Arduino as an FTDI programmer *without removing the chip*. Seems like it could be possible using AVRDude, if not the Arduino software (which also uses AVRDude). Or it might be possible by connecting to a different place on the Duemilanove board instead of just the pinouts.

I've searched a lot and while people speculate that the chip can be left in, and it will just program both chips, that is not what I'm finding. Only the chip in the Arduino gets the new sketch.


"Uploading Using an Arduino Board
Once your ATmega328p has the Arduino bootloader on it, you can upload programs to it using the USB-to-serial convertor (FTDI chip) on an Arduino board. To do, you remove the microcontroller from the Arduino board..."
6  Using Arduino / Interfacing w/ Software on the Computer / SOLVED:Sketches to breadboard-arduino..without removing the real Arduino's chip? on: February 18, 2012, 03:58:51 pm
There are good instructions for uploading sketches to a breadboard-arduino using an existing (real) Arduino, wired them up like this- . But my pins are about to break from pulling the chip several times.

I am able to burn the bootloader using the following command line:
avrdude -F -p m328p -c arduino -P com3 -b 56000 -u -v  -U flash:w:AT328.hex   ..Success!

I can successfully (inadvertently) upload files to the Duemilanove's chip using the same, even though I'm actually trying to program the connected breadboard arduino:
avrdude -F -p m328p -c arduino -P com3 -b 56000 -u -v  -U flash:w:twoblinks.hex  (it even accepts 328P as the chip since -F ignores the signature)

The breadboard ATMega328P has the bootloader and I can program it if I put it in the Duemilanove board, so the chip seems to be working fine. However, I don't know how to use the FTDI serial on the Duemilanove to program off-board without pulling the chip on the Duemilanove.

I could sure use help on wiring it up correctly. Any ideas?
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