On Sat, Jun 23, 2001 at 09:39:57AM -0700, Wade Carpenter wrote:
> Any reccomendations from anyone using this device?
>  I am having trouble finding information on ICSP,

It's easy to find. Download it here:

http://www.microchip.com/10/lit/suppdoc/specs/39025e/index.htm

> so I am trying to build a parallel port programmer.
>  Has anyone done this with success?

For the most part you can program it with 16F84 programming hardware. Same
hardware interface, same programming interface, and compatible programming
sequences. The 16F87X sequence can be optimized, but programming with the
16F84 sequence works just fine.

Also you can drop the High Voltage Programming circuit and use Low Voltage
Programming (LVP). At that point it's little more than a cable. I described
it in a post over a year ago here:

http://www.infosite.com/%7Ejkeyzer/piclist/2000/Mar/2126.html

The login and password are both the name of this mailing list (in lowercase).

I finally got around to building one of these cables. It didn't work. I figured
out that modern motherboard parallel ports only output 3.3V for a high voltage.
It's fine for TTL, which only requires 2.0V for a high signal. However PICs
are CMOS devices and are only happy with high voltages above 4V (presuming a
5V supply, which BTW you need for LVP). So what I did was add a TTL to CMOS
converter between the parallel port and the PIC. I chose a 74HCT573 octal
latch because I had one handy. But any HCT part that will buffer will work
just as well (like a HCT541, HCT241, HCT373, or even an HCT04 if you can
change the polarity of the signals in your programming software).

Worked like a champ. One chip, one resistor, and 5V power.
Can't ask for much less than that.

Now software wise I'm not sure what's the best on the DOS/Windows side. Since
I'm a Linux guy I use picprg2.3a originally written by Brian Lane. My students
and I updated the software with the new erase/initialize sequence and changed
the port code so that it works properly with Linux 2.2 and 2.4 kernels.

Now the last issue is long term development programming. I happen to swear
by wloader written by Wouter van Ooijen. It's a bootloader that you program
into the 16F87X part. That loader will then download programs via a serial
interface. I love it because it cost only one I/O pin, which you can pick
(the default binary uses E2, so you'd have to pick another for the 16F876
part), requires a 4 resistor, 1 diode, progamming dongle (with one added
transistor, 2 resistors, and diode for the automatic reset circuit), and
can be programmed from any serial port in circuit. It's a little pricy
on memory (1K nominal), but I wouldn't use anything else. For my Linux box
I use gpasm and gpsim (I need to upgrade to 0.9.7, right Scott?) , linwload by
Wojtek Zabolotny, and wloader. For development, just hook up the dongle,
program and test, and when I'm finished just disconnect the dongle for a
working product. As a bonus the wloader serial port can be used as a debugging
port.

Just some thoughts. Hope they help.

BAJ

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