Post by thread:Beginners question

I would really appreciate any advice from the list on a program I am going to write for a 16c54. The program will basically "pick out" a pulse of a certain duration ( about 10 microseconds ) at one of the inputs from other pulses which are a little larger and a little smaller.I have a pretty good idea on how to write the code for this program, and I would like some advice from more experienced programmers on how they would write code for this program. Thanx in advance Dominic

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---------- > From: dikelloway <dikellowayKILLspamKBDNET.NET.AU> > To: .....PICLISTKILLspam.....MITVMA.MIT.EDU > Subject: Beginners question > Date: 31. maaliskuuta 1999 7:59 > > PICsters, > > I am new to the PIC environment. > > I am considering using the 16F84 PIC and programming the device in > circuit. > I am assuming that it requires a voltage level shifter if using the > rs232 computer serial > port if programming in this manner. Is this correct ? > > And what about the parallel port ? > > Regards > dmk Yes, this is true. If you want to use RS-232 you will need level shifter. Personally i use MAX232 chip for the job. What about parallel port? If your pic is running on 5V and ground is connected there should be no problem as long as pic and pc don't try to drive same time (ie. both as outputs). J.M. Vehasmaa Version: PGPfreeware 5.5.3i for non-commercial use <http://www.pgpi.com>

Well, lets see... I never had any problem connecting TTL levels to RS232, without any conversion, except inverting the level of course. PC's RS232 chips can understand pretty well inverted TTL levels (<+0.5 as mark and >+4.5V as space RS232 levels). For some testing purposes and (ahammm) also for some "workable" possibilities, you don't need to convert to RS232 level (<-4.5 for mark and >+4.5 for space). A simple 74hct04 or hct14 can do a pretty job of signal inverting, while a simple 10k resistor in series with the hct04 input is enough to block the negative swing from the PC RS232 at the RX circuit. You can incorporate a diode from the junction resistor-hct04 to Ground (anode to ground) to ... protect a little bit the 74hct04, not totally necessary. Well, if you have any communication problems, suspect about this tricky thing, but, I never had any problem, up to now. About the Parallel port, there is a strong recommendation to never Ground a PC output pin, you can pull it down, but never a hard ground, even when the PC parallel port is programmed for bi-directional. To read more about this issue, just search "pc parallel" at altavista, you will find several posts. Wagner Jurva-Markus Vehasmaa wrote: {Quote hidden}> > ---------- > > From: dikelloway <EraseMEdikellowayspam_OUTTakeThisOuTKBDNET.NET.AU> > > To: PICLISTspam_OUTMITVMA.MIT.EDU > > Subject: Beginners question > > Date: 31. maaliskuuta 1999 7:59 > > > > PICsters, > > > > I am new to the PIC environment. > > > > I am considering using the 16F84 PIC and programming the device in > > circuit. > > I am assuming that it requires a voltage level shifter if using the > > rs232 computer serial > > port if programming in this manner. Is this correct ? > > > > And what about the parallel port ? > > > > Regards > > dmk > > Yes, this is true. If you want to use RS-232 you will need level shifter. > Personally > i use MAX232 chip for the job. > > What about parallel port? If your pic is running on 5V and ground is > connected > there should be no problem as long as pic and pc don't try to drive same > time > (ie. both as outputs). > > J.M. Vehasmaa > Version: PGPfreeware 5.5.3i for non-commercial use <http://www.pgpi.com>