16F877 universal PCB with I/O module

I am reposting my 877mCu schematic and silk screen images along with the schematic and silkscreen of an I/O module that interfaces to it. I am reposting so that all of the image links will be in one thread. Again, I can't post the artwork used to create these boards but I can post the schematics. PM me if you are interested in buying these boards for cheap.

Here are the features of each board.

877mCu: This board has the 877, a regulator, crystal, i2c seeprom, RS-232, programming header, reset switch, LCD connector, I/O header and a few other features.

I/O module: This board interfaces with the 877mCu PCB. It is the same size and may be mounted above the other PCB. This board has 8 digital inputs that are optically isolated with LED indicators, 3 outputs that are NPN open collector and can be hardware PWM (also with LED indicators), and 4 analog inputs that can be pots mounted on or off board. The analog inputs could also be configured as digital TTL inputs or outputs.

I have been using these boards in projects for a couple of years now. I hope that these schematics prove useful to others.

Regards,

Joe Kupcha.

Heres the silkscreen for the above schematic.

Regards,

Joe Kupcha

Here is the schematic for the I/O module.

Regards,

Joe Kupcha.

Here's the last one. This is the silkscreen for the I/O module.




Regards,

Joe Kupcha

Is there any PCB layout available ???

Thanks

Joe,
I'm interested in your board. I'm working toward a small board with 16x2 LCD,
2 or 3 a/d inputs and possibly a PWM out.
Couple of questions:
1. What size is the board
2. How does the LCD connect. I haven't found an easy way to accomplish that yet
Thanks,
John

I have downloaded the schematic, and it looks good.
Helped me make a board using F877 for the first time.

Just a Q for anyone who can answer, is there a reason why the two pins
used for comm with the EEPROM would be sourced
from an 8 bit port rather than portA 5 bit port? Using two pins from an 8
bit port seem a waste of a port that has byte-wide I/O potential.

I would like to use A0 as a sink for indicator LED,
A1 SDA, A2 SCL, A3 SDA, A4 SDL for IIC EEPROMS.
Is one of the portA pins only an input?
Cheers, Art.

The main reason IMHO is because the PORTA is analogue so, when you need to read an analogue signal and you have your EPROM attach to, you're in the FadeleeFadelaa!

There is an small error where portd5 is labled c5 on the picture of the pic.
This error caused my house to burn down. will you pay for damages?

Just kidding, since I want all digital ports I started from porta.

are the resistors connected to a5 there to set a reference for analogue ports?

Art,

The resistor network on A5 can be used to monitor the input voltage.

Sorry for the small error. You are correct the schematic has D5 mislabeled.

As for why I used two pins of port C to conrol the SEEPROM...well those are the SSP I2C pins for clock and data.

I had good reason for using most of the pins the way I did. I left A4 unused but I wanted to set it up as another output but just never got around to it. A4 has an NPN open collector output. Very handy.


Please post any questions. I can't promise I will answer in a timely manner but I will eventually check back here.

Regards,

Joe.

edit: I almost forgot. Analog ports are very powerful/useful. I use them alot.

Do you have any pcb layout available ?

I still use this board in commercial projects and I can't make the artwork freely available. I can tell you that it is a breeze to layout. I have posted the silkscreen images and I can sell the boards (at a little over my cost plus shipping). PM me if you are interested in purchasing. I also have I/O modules that interface with the univeral 877 board.

Hope this answers your question.


Joe.

Joe,

Nice lookin' board... I use the space inside machined pin sockets to reduce board space even further... I suspect it's not "good practice" but it's been helpful on a few designs... The 0.1uf mono' caps' are Kemet 310 or 315 series (physically very small)...

Regards, Mike