Post by thread:[PIC] Interfacing a PIC with the parallel Port pro

Hi all Just to check if any have the same problem too i am current measuring the voltage that coem out from the paralle port. it varies from PC to PC ranging from 3.3 to 5 voltage. and when operate in EPP mode some PC have signal out of the address strode and does not what can be the problem that cause this please advise. if i am want to interface the paarlle port at 3.3 voltage to the PIC what is a good buffer/ level shifter to used? Regards WebSite : http://soonlee.agreatserver.com

L030010 wrote : > Hi all > > Just to check if any have the same problem too > > i am current measuring the voltage that coem out from the > paralle port. it varies from PC to PC ranging from 3.3 to 5 > voltage. and when operate in EPP mode some PC have signal out > of the address strode and does not > > what can be the problem that cause this please advise. What "problem" ? Doesn't your par port work as it should ? > if i am want to interface the paarlle port at 3.3 voltage to > the PIC what is a good buffer/ level shifter to used? Why do you want your PIC to be connected to the par port ? Why not use the serial port instead ? Jan-Erik.

On Mon, Apr 18, 2005 at 09:55:27PM +0800, L030010 wrote: > Hi all > > Just to check if any have the same problem too It's not a problem. > > i am current measuring the voltage that coem out from the paralle port. it > varies from PC to PC ranging from 3.3 to 5 voltage. and when operate in EPP > mode some PC have signal out of the address strode and does not That's a standard PC parallel port. They are only guaranteed to output TTL voltage, which is 2.4V. Most modern PC parallel ports output at the 3.3V level. > what can be the problem that cause this please advise. There is no problem. That's the way it's designed. > > if i am want to interface the paarlle port at 3.3 voltage to the PIC what > is a good buffer/ level shifter to used? For my Trivial Programmers I'm using HCT family parts, specifically the 74HCT573. The TTL compatible inputs work fine with the 3.3V input from the parallel port, while the CMOS outputs are virtually rail to rail registering near 0V for low signals and nearly 5V for high signals. My front PIC/programming page at http://www.finitesite.com/d3jsys describes the exact situation you are having. One last issue that I haven't really gotten a handle on is that if your parallel cable is too long, you'll get transmission line effects. I attempted an AC termination scheme for my programmer, but didn't get real good results. BAJ

> if i am want to interface the paarlle port at 3.3 voltage to the PIC > what is a good buffer/ level shifter to used? Fairchild Semiconductor 74LVX161284; full 8-bit bidirectional data bus plus sufficient control & status lines to implement a standard IEEE-1284 parallel port. Datasheet and app notes assume you will be using it on the peripheral side. It can also be used for host side (which we are doing); just be carefull how you wire it up. CPU side is 3.3V. Cable side has seperate power pins, so you can run cable side at 5V. Works nicely to interface 3.3V PIC to printers. Lee Jones