Shift Registers

Archiver

I would like to know how to interface a 4 digit 7
segment led and program with a shift register(maybe
74hc595).
I would like to display some value from 0000 to 9999
(rpm) from a tachometer.

Thank you very much
Alejandro Vazquez

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Archiver

The easiest way is to simply have more than one register, tie the clock and
data together and independently strobe the latch's.

A while a go I did it a bit differently. There would be one shift register,
a 164 would do, connected to the inputs of 4 octal latches. A 4017 with
it's clock connected to the stamp and it's outputs to the latch of the 4
latches (0 - 3) would be clocked after a new digit was outputted causing the
last latch to remember the input. To display the contents of the latches,
the outputs of each latch were tied together creating another bus. A 4017
with an oscillator was connected to the tri state inputs of the latches and
a transistor was also connected to the common of the corresponding display.

As the oscillator cycled the 4017, it's output will set one latch to output
mode, and turn on one digit, displaying the contents of that latch.

You need to write the entire display over every time you update it. You can
store the digit format in the data eeprom and play with some address
addition.

cnvt:
pulsout resc,1
num2 = x DIG 2
numa = num2
gosub show
num1 = x dig 1
numa = num1
gosub show
num0 = x dig 0
numa = num0
gosub show
return

show:
read digit0 + numa,digit
shiftout dispdat,dispclk,1,[noparse][[/noparse]digit]
pulsout wrtclk,1
return

After making this I saw how convenient a LCD display is.

There is also a one chip solution for this exact thing.

Mike

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Original Message

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From: "Alejandro Vazquez" <alexvazquez@y...>
To: <basicstamps@egroups.com>
Sent: Monday, May 29, 2000 3:18 PM
Subject: [noparse][[/noparse]basicstamps] Shift Registers


> I would like to know how to interface a 4 digit 7
> segment led and program with a shift register(maybe
> 74hc595).
> I would like to display some value from 0000 to 9999
> (rpm) from a tachometer.
>
> Thank you very much
> Alejandro Vazquez
>
> __________________________________________________
> Do You Yahoo!?
> Kick off your party with Yahoo! Invites.
> http://invites.yahoo.com/
>
>
>
>