Broken/Fried Parallel port...

Hello all, I have been working with an interfacing project lately and I think I have "screwed up" my parallel port. When trying to read data from the data register (set from an A/D converter) I wasn't getting correct results. After some "experimenting" I realized one of the pins isn't going "high" when being supplied voltage. Anyway, it seems if I connect this pin directly to the +5 from the 7805 regulator it goes high, but the A/D converter IC doesn't seem to se the pin high. I use a multimeter and figured that this pin needs at leats 18mA to go high while all the others need about 2 (maybe less). SO, my question is, is this normal? Do specific pins on a parallel port act that differently from eachother or have I fried something inside my laptop? Nonetheless, my port still works, I just altered its functionality. So how could I use my A/D converter to throw this malfunctioning parallel port pin high? Could I use a transistor (2N3904?!?) somehow? Any help would be excellent. THanks, Lucas.

Reply to
lmcgill2
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Lucas, given that you have one bit responding unlike the others, you have likey somehow fried something.

Were you now using a laptop, I would have suggest that you simply plug in another serial interface board, but using a laptop this is generally impossible. This is one of the reasons why most of us interfacing out PCs with something else use desktops with expansion slots. A $20 parallel interface card is a good deal cheaper than replacing a $2,000 laptop, and good luck if you have to try and repair it.

Then too, there is alway the hope that you diagnosis of the problem is incorrect. Personally I'd do some more tests before declaring the interface on the laptop toast, since you really have to do something really gross to destroy a parallel interface (which I assume you mean a printer port). Did you try and test it with a printer to see if it worked with that? That's what I would try first, just to distinquish a problem with and a/d converter vs a problem with the laptop.

Good luck.

Harry C.

snipped-for-privacy@uiuc.edu wrote:

Reply to
hhc314

In this case parallel interface card...

Sand and true. Many laptops have USB interface, and there are USB to parallel port adapters. Those adapters are generaly OK for connecting norma printers as such, but not usually suitable for many homebuilt electronics projects (they can't be controlled with sofware like original PC parallel port could).

This is a good advice. There are many different parallel port cards out there. They generally work well with normal printer, but depending on their type they work or might not work with the software designed for normal parallel port.

On old PCs with ISA bus the expansion parallel ports were simple and easy. Typically same handware as original port, just different standardized I/O address. Direct I/O port level accessing works when you just change I/O address.

PCI bus paralle port cards are different story. Those PCI port parallel ports genrally use more or less different hardware than ISA counterparts, and use entirely different I/O addresses (there might be some that cna be configured). With most PCI bus based parallel port the old fashioned I/O port lever parallel port controlling fails. The software that is written in this way fails. This means that generally the parallel port contolling software and many paralle port gadgets fail to work with parallel ports on PCI us expansion card.

USB parallel port interfaces are entirely different in architecture than legacy PC parallel ports. Parallel port contolling software and many paralle port gadgets fail to work with parallel ports on PCI us expansion card.

I am still looking for the details how those coudl be used for general purpose I/O like the parallel port on PC motherboard or in ISA bus expansion cards. Details may be one day added to this document on parallel port controlling:

Parallel port interfacing made easy

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Tomi Engdahl (http://www.iki.fi/then/)
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Reply to
Tomi Holger Engdahl

Is this a data pin or a status pin on the port that you are attempting to read?

I would not connect the 5V direct as this will cause problems is the device is at a low level. It is better to use a 1K resistor tied to the

5V as a pull up.

A 1K resistor to 5V is 5MA and should be sufficient. I suspect the port is not set to input mode if you are using a data bit.

Data pins are different from Status pins and some status pins have inverted levels.

I don't have my chart handy, please indicate what Pin numbers you are using.

Dave

Reply to
CheapscateDave

Thanks Dave for the help, I am trying to read from the data register. To my knowledge, the 0-bit of the data register is pin 2 on the parallel port, and the 7-bit is pin 9. The pin that is giving me wierd results is pin 8. When i say wierd i mean it won't go "high" when being told to do so by my ADC IC. In addition, my port is in bi-direction mode, thanks, Lucas.

Reply to
lmcgill2

You might want to consider using the parallel port status lines to input your data. You would probably need two ADC chips to do this, but it might be an easier setup. I've made the below setup to input data into my parallel port.

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Reply to
Si Ballenger

Try connecting the laptop to a normal printer. If it works, the you are lucky and you should probably stop experimenting with the laptop and get a cheap second-hand computer with an ISA bus or PCI printer port card that you can replace when you blow it up. I have damaged a parallel port card, I think there was a static charge on a long cable when I plugged it in. I was very pleased that it wasn't a laptop.

Some of the printer port pins can be programmed to be either inputs or outputs, and it may be that the pin thinks it is an output. On some PCs I never succeeded in making the main data lines of the printer port act as inputs and I had to use a MUX chip on one of the status lines to read in the bits one at a time instead of using the data lines.

Chris

Reply to
Chris Jones

schreef in bericht news: snipped-for-privacy@x69g2000cwx.googlegroups.com...

Hmm... There are several tastes of parallel (printer) ports. In todays PCs, you can usually choose the taste in the BIOS setup. Guess this is the first thing you have to find out. Have a look at

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part of parallel port interfacing for an overview. The same chapter also describes a DOS tool for parallel port debugging.

petrus bitbyter

Reply to
petrus bitbyter

Lucas, What I would do at this point is get 8 1K resistors and 8LEDs. Connect -(minus)lead of each LED to pins 2 to 9, +lead of LED to each

1K resistor and all of the 1K resistors to your +5volt supply. When the port is in output mode a 1 bit will turn the led off, a 0 bit will turn the bit on. When the port is in input mode it should read FF or 1 bit for each pin. Starting with pin 2 start grounding the - LED lead and read the port, remaining in input mode. When the pin is grounded the LED should light and the port should read a 0 for that bit. Hope you can step your program to accomplish this.

Dave

Reply to
CheapscateDave

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