Who knows their electronics!

[Vadoo]

Who here knows the deep inner workings of the Grinch, and wouldnt mind if i pm them with some questions?

[daviddth]

Post them in here - there is bound to be people who know the answers.

[Vadoo]

Ok then lets start with the MBI5027. What better place to start then how does it work?

This page shows the names for the pins being used from the paralell port to be +STROBE, +DATA0, and +AUTOFEED.
http://computerchristmas.com/christm...el_Port_Pinout

The MBI5027 data sheet shows the pins used named as SDI, CLK, and LE(ED1).
http://www.kingelectronics.com/image...02-English.pdf

I would like to learn the link between the two different names for the connections, and what each one means and does, how the chip uses these inputs.
Yes i can find the answers in a number of places, and i have, but i need someone to dumb it down a little!

[prof]

In a nut shell the names of the pins on the parallel port only apply to the function they perform as a parallel printer port. It is what they are being programmed to do when controlling the grinch that matters.

The three main parts of the MBI5027 are: a 16 bit shift register, output latch and output driver for the LEDs.

The SDI input (serial data in) receives the data for the outputs on the chip(s) (0=off 1=on).

The CLK input is the clock signal that pulses high for every bit of data that needs to be sent to the chip(s). (16 times for 1 chip, 64 times for 1 grinch board etc)

Each time CLK pulses high the value present on SDI is moved into the first bit of the shift register and any data already in the shift register gets moved along. 16 clock pulses and the first chip is loaded, the 17th clock pulse starts loading into the next chip, 64 clock pulses (4 chips) and the grinch board is loaded.

The LE input is the data latch. When all the data has been loaded into the chip(s) this input is pulsed high to place the data in the shift registers into the output latch and hence into the output driver.

Hope I have got it right (and made it simple enough)

[Vadoo]

That makes sense.
Next one I'm curiouse about is R-EXT. From what I understand this is where the output voltage comes from? And it can be addjusted/lowered with a resistor if it were necessary?

Also OE(ED2). Although it is not used for our purposes, I'm curiouse what it could be used for.

[Wombat]

The chip has inbuilt constant current outputs for all of the 16 outputs on the chip. The resistor sets the current that the outputs are set to. The lower the resistor the more current on the output.

Wombat

[Wombat]

OE is an output enable pin. This allows you to turn all of the outputs off at once. This does not change what is set in the registers and making the output low enables all of the outputs again to thier previous value.

[Vadoo]

Could you put +5v R-EXT for a +output?

[Wombat]

Not sure what you mean by that but if you are talking about can you have logic 1 or 5V outputs instead of current limiting ones then its already there. if you are not drawing more than the current limited value from the outputs they will be at 5V potential.

Is that what you are getting at?

Wombat

[Vadoo]

The outputs send a -5v when turned on right?
Is that because R-EXT input is -5v?
Could you apply +5v to R-EXT and get a +5v out of the inputs when they are turned on?