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AVR ISP power supply through parallel port Answered

Hi I am building an AVR ISP and it requires a 5V power supply (for 74LS541 and the AVR). I have done some googling but found it to be confusing. Does anyone know how to get a 5V power supply from the parallel port? Thanks



10 years ago

There isn't a voltage tap on the parport (which I guess you figured out.) Use an external regulated supply. I use a 5V bench supply for development, and a 5v regulated wallwart for project.

not surprising at all..(personally i dont like external supplies) i guess i'll get usb and ps/2 power

thank you all for the help =]

Sure. I'd just be a bit careful if you power the whole project from those ports. It'll work fine for a small project. But both ports have a current limit, and neither actively enforces that limit (it's up to the connected device itself.) I've certainly heard about people frying USB ports by drawing too much current.

by the way, can i use one zero insertion force socket for 8 pin ATtiny85ATtiny85, 40pin ATmega644ATmega644, 20pin ATtiny861ATtiny861, and 14pin ATtiny84ATtiny84, etc? i know they have different lengths and widths, but the ZIF socket looks like it could take them all, just have to big enough to fit the microcontrollers, right?

Yes, it's standard practice to use a 40 pin ZIF socket for programmers (like the AVR dragon), but....

Since the actual ISP signal lines (and RESET) are in different places for each IC, the lines are not "hard-wired." Instead, header-pins are connected with a set of temporary jumpers to complete the connections.

Look at the Dragon PDF, page 18 --it shows the ZIF, with jumpers. Pages 19+ display the jumper settings for different AVRs.

The older STK500 board has jumpers too, although setting them is simpler than the Dragon. It's setup is simpler due to the fact that they used 8 separate sockets, not one ZIF.

Great! Building this ISP is my first project..I am glad I designed the board right by hooking up the jumpers/header pins (i dont know what it really is called haha) to the ZIF. let me simplify the frying situation (just checking if i got it right): preventions from frying the computer ports are simply like to lessen/take off the load or the things connected to it thanks

Yep, too much load (too many components) will overtax the port.

If you feel the AVR ISP project is too much, the DAPA ISP can be made with fewer components. Here's an example on instructables: Ghetto programming AVRs. This is the type mentioned by Zach.

You will need external power, though. Since most projects will eventually be powered (by batteries, etc.), anyway--not a big thing. It's common practice to include a DAPA connector on the project board, so reprogramming can be done without removing the AVR.

interesting it doesnt use any buffer chip! i got the AVR ISP schematic off a book. it doesnt explain the schematic though, which is pretty bad, like why the capacitor is used and why connect to this or that paraport pin. i was actually goin to start 8051 few months ago, but was convinced that AVR is much much better. I have heard that AVRs doesnt need external clock/crystal, but the book from the library uses it. whats that about? yes, i am all new to this microcontroller stuff (well actually 90% percent of electronics) its pretty hard when there are no books around about electronics, but i am trying to hang on, even though it may be a large "project"
below is the schematic I "designed" using eagle. I am almost done with my first board! Yay. even though all this may seem pretty hard (to me), i am actually having a great time =]


I don't want to discourage you from completing your project! Just to giving you another option, as you indicated you were a noob ;-)

Yes, if you use the recent AVRs (ATmega or ATtiny) you don't need an Xtal. The internal oscillator is running at 1 mHz by default.

I found this article by Guido Socher very useful. It outlines the DAPA cable, and also has a minimalist project, with a good schematic. The article is a bit dated, as it emphasizes UISP over AVRDUDE, but he includes a script that can use either (for programming space or fuses.)

He has several other more complex projects, too.

Re: cap in "ghetto programming"--I couldn't even find that schematic. But adding a 10uF cap as an extra 'filter cap' is standard for projects (it's usually included on all the Atmel datasheet examples.)

Wow the link is wonderful! Easy and simple, just beautiful. I am beginning to think the schematic I am using is a bit too complex, but all the components are there for a reason. I am glad; it's all part of the learning process- and asking millions of questions too =) I am beginning to understand the cap and the diode are for filtering the unwanted stuffs. For the buffer, I am not sure, but my mind got to a conclusion that it is "preventing data traffic from happening". I should start thinking about "how the data is burned to the AVR". These things are so interesting!
Thank you so much for helping and your patience =)

Cool, glad it helps. Again, I don't want to dissuade you from building that ISP circuit--only to offer a simpler one.

The buffer chip in the AVR ISP (clone) circuit is present largely to protect your parallel port (which is also the purpose of the current-limiting resistors on the DAPA ISP cable.) Also, if you cut power to the buffer, removing/inserting an AVR shouldn't effect the parport.

The AVR ISP programmer is probably safer for your computer, but I (and many others) have had no problems using the DAPA ISP.

It is even possible to connect/disconnect the DAPA cable with the computer on, by removing any power to the AVR circuit. Whether it is wise, or not....??? (A cautious person would power down both.)

One more thing about the (Socher) article: don't feel you need to use his custom CDrom. Any current Debian distribution will give you access to the AVR software (I use Xubuntu on an older computer.) Or, winavr for the windows OS can work, too.

hmmm I thought different programs (software) goes with their own programmer schematic? The pins that are used on the paraport is different

If you use avrdude (open source) you can set which ISP programmer you are using.

For instance to verify an ATtiny2313--

avrdude -c dapa -p t2313 -v

The -c option sets the programmer type (DAPA here.) Look under the -c section of the AVRDUDE Option Descriptions. I'm not even sure you could use avrisp as an option with your build, as it's normally a serial interface mode--but one of the options would work.

Commercial programmers would have their own software, of course (bascom, pony prog, Atmel, etc.) But most work with avrdude, too.

This earlier thread on instructables has info, too.

Just to giving you another option

????? :D We really could use an 'edit' option...

i dont think the ISP i m using will fry the port though is there anything i can add to prevent the frying? thanks

Just limit what you connect, if you're prototyping and not just programming.

The PS/2 spec is for a max of 275 mA--but if you're sharing that current with the keyboard or mouse, you'll have less. The programmer and target AVR alone won't be a problem.

Well, I've been able to program AVRs using only the power from the paraport. It isn't able to verify it, though, but it does program.

what do u mean by "verify"? do u have a schematic for that ISP?
thanks =]

When you program them, avrdude, and I'm going to guess that most other uploaders, read back what was written, to make sure it got programmed correctly. The AVR, without power, won't be read, so it fails verification. I don't reccomend this, though. Depending on the AVR, you should be able to power it off of 3V...

yeah 3V is actually pretty nice but my paraport goes up to 2V..a bit dangerous for programming

I've seen them respond (with the device #, etc.) in some 'parasitic' fashion when connected with a DAPA cable (which doesn't even have a + voltage supply pin.) But I haven't been brave enough to actually try programming 'em.

just tap into the 5 volt rail on the molex connectors then.

i am using a notebook. ive thought of using the usb, but its too much of a "trouble" to have to cables connected to the ISP

yup, taking in for consideration (personally i dont like external sources)

just use a multimeter. connect ground to the ground line of your computer (12v ground) and probe the other leads with your meter.

oh yeah i tried that. it doesnt reach 5V, only goes up to 2..and plus if the pin's logic is switched to 0, then there will be no power. the thing is i want to have a constant supply of 5V for my ISP