74hc595 seven segment.

Coder96

I picked up some 7 segment modules off ebay. https://ebay.com/itm/74HC595-static-drive-2-3-4-segment-digital-display-module-0-5-inches-2-3-4-way/332337987430?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

They use the sm74hc595d chip.

Any data sheets I found were not in English. Not sure if they can do 3.3v logic.

Has anyone worked with these?

Phil Pilgrim (PhiPi)

According to specs, 74HC logic is pretty marginal with 3.3V signal levels [edit]when powered from 5V[/edit]. 74HCT logic is preferred. Still, I'd still give the modules you ordered a 99% chance of working at 3.3V -- but maybe not under all temperature extremes.

-Phil

mikeologist

This is the data sheet for the ic.

mikeologist

You typed sm, it's sn

Coder96

Looks like a M to me



These are how they labeled the pins.



If i had all the segments on. Some of the segments would turn on when testing. Not sure what I'm doing wrong.

I don't have any level shifters around. Might have to order some.

Phil Pilgrim (PhiPi)

"SN" is just a prefix for Texas Instruments products. Other manufacturers have different prefixes. "SM" is the prefix for KeySemi. Neither is part of the generic part number.

-Phil

tomcrawford

Can you show your code? Clocking all "ones" into the shift register (SDI/SCLK) followed by a positive edge on LOAD ought to light up all segments of one digit.

Coder96

This is what I've been testing with.

CON
  _clkmode = xtal1 + pll16x             'Standard clock mode * crystal frequency = 80 MHz
  _xinfreq = 5_000_000

'------Shift Register Pins------
  Latch_Pin         = 19
  Clock_Pin         = 17
  Data_Pin          = 15
  Chip_Num          = 2

OBJ

  data        : "74HC595_Regular"
      
PUB Main 
  
  data.Start(Clock_Pin, Latch_Pin, Data_Pin, Chip_Num)
  
  data.Out(%11111111, 0)
  data.Out(%11111111, 1)
  waitcnt(clkfreq*2+cnt)
  data.Out(%00000000, 0)
  data.Out(%00000000, 1)
  

Phil Pilgrim (PhiPi)

Can you also post the code for 74HC595_Regular.spin? 'Just wanna see what it's doing with your calls.

-Phil

Coder96

It came from the obex or forums some where.

IT's to big to post here so I'll attach it.

tomcrawford

Maybe put a delay after the data.start to be sure the PASM cog is running. Otherwise:

Looking at your code, you are doing everything exactly right.
Also, the really good documentation in 74HC595_Regular makes me think it was probably tested and likely works.

I would try to decide whether it is a hardware (wiring) vs software issue.
I would write a really simple (trivial) spin program to shift out a few bits, followed by a low-to-high transition on Latch_Pin.
If something lights up, you got a software issue.

Coder96

Thanks for taking a look.

I had a flip module show up. So set that up a new bread board with some solid jumper wire.

Working as expected now. Must have been my previous wonky set up.

tomcrawford

Glad you're up and running.