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'[OT] 32-bit Serial-Input Confusion'
2000\04\03@143305 by Nathan Hendler

I have a 16F84 pic and a VFD controlled by an Allegro 5818 32-bit
Serial-Input chip.  I think that maybe I don't understand how the strobe
and blanking lines work, as I can't get the display to do anything useful.

I wrote a real brute force program to send the display 32 bits.  Basically
it looks something like this...

call Init       ; make everything outputs and low
call SendHigh   ; bit1
call SendHigh   ; bit2
call SendLow    ; bit3
call SendHigh   ; bit30
call SendLow    ; bit31
call SendLow    ; bit32
call StrobeVFD  ; raise strobe, pause, lower strobe.

Ok.  That's kind of embarassing, but it allowed me to quickly mess around
with the bits, and see how the VFD responded.

I've learned that the first 16 bits select which characters, and the last
16 bits select the segments.  So if Bits 1, 2 & 3 are high, and bits 17-32
are high, the display will have all segments lit up on characters 14, 15 &
16.  Easy enough.

Well, all I can do is make a bunch of characters display the same
segments, but I can't get two different characters on the display at once.

Can do:

Can't do:

So, my thought was that I need to multiplex the display?  Doesn't seem to
work.  I think maybe it's because I don't really know what I need to be
doing with the Strobe and Blanking lines.  At startup I pulse the blanking
line, but after that I leave it low.  It seems like I shouldn't have to
multiplex the display.  It seems like I should be able to do something

Send serial: 10000000000000001110010000101000
Strobe (high, pause, low)
Send serial: 01000000000000001001110001110100
Strobe (high, pause, low)

... and have two different characters on the display.

I hope someone understands me :)

Nathan Hendler

2000\04\03@145214 by James Paul


Do you have a data sheet for the display?   If so, could you
email me a copy?  My email address is  I'd be glad
to help you out, but I need to see the data sheet so I can
figure out what is supposed to happen and when.   Let me know if
this is helpful.



On Mon, 03 April 2000, Nathan Hendler wrote:

{Quote hidden}

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