[sdiy] I/O trouble...

[phillip m gallo]

Bert,

Sorry, for dropping the link in prev. email.  Also if you are buffering MIDI
(instead of interpreting it as it comes in) you should be able to interleave
the key and LED activity nicely.

 You might want to take a look at this Maxim product page.

http://www.maxim-ic.com/MaximProducts/DisplayDrivers/led-drivers.htm

regards,
p


-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Bert Schiettecatte
Sent: Friday, July 11, 2003 1:36 AM
To: synth-diy at dropmix.xs4all.nl
Subject: RE: [sdiy] I/O trouble...


Hi laurie,



Thanks for your email! I checked those parts on digikey and they are all
obsolete. I’d also like to be able to adjust brightness

through PWM …



I’m actually not sure what will happen if I try to do PWM on the LEDs from
my MCU and the MCU gets interrupted now and

Then by the UART for MIDI communications… ?



Thanks,



bert



-----Original Message-----
From: Elby Designs [mailto:elby_designs at ozemail.com.au]
Sent: vrijdag 11 juli 2003 9:55
To: Bert Schiettecatte
Subject: Re: [sdiy] I/O trouble...



The MM5484 (there are others that are similar) is a 16-segment LED driver
that uses Nationals MicroWire for communications. That is a 3-wire
communications path for 16-segments and 4-wires for 32 segments.

Also check out there MM5450 and MM5451 chips.


Best Regards
Laurie Biddulph
http://www.ozemail.com.au/~boobies
Mobile: 0404 846 943

  ----- Original Message -----

  From: Bert Schiettecatte

  To: synth-diy at dropmix.xs4all.nl

  Sent: Friday, July 11, 2003 9:09 AM

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



  Hi All,



  On my daily adventures with microcontrollers I am faced with another I/O
problem. Please forgive me my silly questions since I’m not an electronics
expert.



  Here goes:



  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).



  Thanks for any suggestions…



  Bert (very tired and going to bed now)





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