Thank you for your feedback, Jean-Pierre. Please send me the pictures of your project if you want to share it with peppe8o’s readers 😉

To simplify I create a library file. I don’t think it’s necessary to give data, clock and latch as arguments during the update.

The library in a file lib74HC595.py

from machine import Pin
import utime

class 74HC595:
”’
Classe class_74HC595
8-bit serial-in/serial or parallel-out shift register with output latches; 3-state

”’
#
#
#
def __init__(self, dataPin, latchPin, clockPin): #
”’
Constructeur :

On y défini les trois signaux de commande du shift register
”’
self.dataPIN = Pin(dataPin, Pin.OUT)
self.latchPIN = Pin(latchPin, Pin.OUT)
self.clockPIN = Pin(clockPin, Pin.OUT)

def update(self, input):
”’
Mise à jour du shift register selon les data dans input

”’
#put latch down to start data sending
self.clockPIN.value(0)
self.latchPIN.value(0)
self.clockPIN.value(1)

#load data in reverse order
for i in range(7, -1, -1):
self.clockPIN.value(0)
self.dataPIN.value(int(input[i]))
self.clockPIN.value(1)

#put latch up to store data on register
self.clocPINk.value(0)
self.latchPIN.value(1)
self.clockPIN.value(1)

Usage in script Raspberry Pico

from lib74HC595 import class_74HC595

..

# Instantiation d’un objet de type 74HC595
shiftRegister = class_74HC595(dataPin, latchPin, clockPin)

# Initialisation (Le shitRegister est en mode Common Anode, Inversion)
bit_string=”11111111″
shiftRegister.update(bit_string)

… later

bit_string=”00000000″

while True:
update(bit_string)
bit_string = str(random.randint(0, 1))+bit_string[:-1]
utime.sleep(0.3)

Thank you for your feedback and for the proposed code alternative, David!

**********************************************

from machine import Pin, Timer
import random

#define PINs according to cabling
dataPIN = 19
latchPIN = 17
clockPIN = 18

#set pins to output PIN objects
dataPIN=Pin(dataPIN, Pin.OUT)
latchPIN=Pin(latchPIN, Pin.OUT)
clockPIN=Pin(clockPIN, Pin.OUT)

bit_string=”0000000000000000″

#define shift register update function
def shift_update(tim):

# get the previously defined global values.
global bit_string
global dataPIN
global clockPIN
global latchPIN

#put latch down to start data sending
clockPIN.value(0)
latchPIN.value(0)
clockPIN.value(1)

#load data in reverse order
for i in range(15, -1, -1):
clockPIN.value(0)
dataPIN.value(int(bit_string[i]))
clockPIN.value(1)

#put latch up to store data on register
clockPIN.value(0)
latchPIN.value(1)
clockPIN.value(1)

bit_string = str(random.randint(0, 1))+bit_string[:-1]

def main():

#start the timer, calling shift register function as a callback
Timer(-1).init(period=100, mode=Timer.PERIODIC, callback=shift_update)

if __name__==”__main__”:
main()

Please, can you send me a photo of your wiring? Send it to my email address: giuseppe@peppe8o.com

Yeah, I thought it could be power, so replaced Pico with buttons, and attached 5V source. Clicking the buttons I can make diods blinking, still situation is the same… It works only when any 7 of them are connected (except q0)… I think this 74hc595 can be just broken

It seems to me that the power passed to the Pico may not be enough in your case. Try changing the power source

Hi GioH.
To manage multiple Shift registers, you can put them in serial connection or in parallel.
In serial connection, you attach the serialout of first SR to data of second and so on. Latch for allow SR are connected together, same forclock. You can use my code, running it as times as the number of connected SR:at the first update you load data for last SR, then you update data for the prev one and so in up to the first.
Parallel configuration require one GP for each data, while clock and latch are still together. In this case you need to change my code.
For quite all project, the serial configuration is the best option as the SR are so fast that user will never see intermediate effects