AW: [sdiy] I/O trouble...

[bschiett]

hi peter,

I tried farnell and digikey but no trace of the intel 8279 controller :(

bert

Quoting Ullrich Peter <peter.ullrich at kapsch.net>:

> >I have a MCU with 2 8-bit ports available, one of them is the A/D. Since
> I'm
> connecting an LCD to the MCU as well, I need one port as the LCD's data bus.
> 
> >So that leaves me without any pins to light my LED matrix (32 leds = 4x8)
> and
> scan my key matrix (up to 32 keys). 
> > 
> >I thought about putting an SN74CBT16233 on the 2 8-bit ports, this will give
> me
> another 16 I/O lines. This IC is a 16-bit 1-of-2 FET multiplexer. So I would
> 
> >put the A/D and LCD data bus on one output of the multiplexer and the key
> matrix + led matrix on the other output of the multiplexer. The key and led
> matrix 
> >would be 8 rows which I want to put power on sequentially, and then use 4
> columns to light the LEDs and 4 columns to scan the keys. Does this make 
> >any sense? I'm just trying to find a way to hook up all this I/O. Argh! 
> > 
> >It's ok if I lose some brightness by multiplexing, as long as they have a
> decent visibility I'm happy. I'm also concerned that the MCU might go to
> heaven
> if I 
> >make it source and sink the current for the LEDs (even when only one LED
> gets
> lit at a time for a very short period). 
>  
> You could attach an 8279 keyboard/display controller to the microcontroller
> bus!
> 
> This controller can scan a keyboard with I think about 64 keys and can
> control 
> 8x8 LEDs. You get an interrupt when a key is pressed, too.
> 
> I used this part sometimes and it works fine!
> 
> datasheet is here: http://my.dreamwiz.com/pentam/databook/8279.pdf
> 
> But before using it check the availability!
> 
> Ciao
> Peter
> 
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