Read multiple digits from 4x4 keypad using raspberry pi 3

Question

I am doing some attendance related project. Where I am using 4x4 keypad and a LCD display. So the question is, How can I read more than one number from a 4x4 matrix keypad?. I am using pad4pi library. Where I am allowed to read only single number or digit at a time. Now I want to read a number like 1234 or 12345. Could you please help me.

Answer 1

Storing a sequence of keys could be facilitated by using a data structure to store the pressed values. And then clearing it when you need to reset.

class KeyStore:
    def __init__(self):
        #list to store them
        self.pressed_keys = []

    #function to add to list
   def store_key(self,key):
       if(key==‘#’):
      #im printing but you should do whatever it is you intend to do with the sequence of keys. 
      print(self.pressed_keys)
 else:
      self.pressed_keys.append(key)

    #function to clear list
    def clear_keys(self):
        self.pressed_keys.clear()

keys = KeyStore()

# store_key will be called each time a keypad button is pressed
keypad.registerKeyPressHandler(keys.store_key)

Answer 2

I did this but still I am stucked

from pad4pi import rpi_gpio
import time


# Setup Keypad
KEYPAD = [
        ["1","2","3","A"],
        ["4","5","6","B"],
        ["7","8","9","C"],
        ["*","0","#","D"]
]

# same as calling: factory.create_4_by_4_keypad, still we put here fyi:
ROW_PINS = [16, 20, 21, 5] # BCM numbering; Board numbering is: 7,8,10,11 (see pinout.xyz/)
COL_PINS = [6, 13, 19, 26] # BCM numbering; Board numbering is: 12,13,15,16 (see pinout.xyz/)

factory = rpi_gpio.KeypadFactory()

# Try keypad = factory.create_4_by_3_keypad() or 
# Try keypad = factory.create_4_by_4_keypad() #for reasonable defaults
# or define your own:
keypad = factory.create_keypad(keypad=KEYPAD, row_pins=ROW_PINS, col_pins=COL_PINS)


class KeyStore:
    def __init__(self):
        #list to store them
        self.pressed_keys =[]

    #function to add to list
    def store_key(self, key):
        self.pressed_keys.append(key)

    #function to clear list
    def clear_keys(self):
        self.pressed_keys.clear()

keys = KeyStore()

# store_key will be called each time a keypad button is pressed
keypad.registerKeyPressHandler(keys.store_key)
for key in keys.pressed_keys:
    print(key)

try:
    while(True):
        time.sleep(0.2)
except:
    keypad.cleanup()

But its not doing anything.

Answer 3

Thanks for showing me. That code isn't going to do anything. You have to actually do something with the stored data structure after registering keys.

For example:

#change store key function to do something on submission of a certain key that indicated send, will use pound for example.
def store_key(self,key):
     If(key==‘#’):
          #im printing but you should do whatever it is you intend to do with the sequence of keys. 
          print(self.pressed_keys)
     else:
          self.pressed_keys.append(key)

That code will print the internal data structure on # being pressed. Of course I'm assuming the key passed on is a string, but I don't really know I'm not familiar with the library.

Answer 4

here is my code according to changes.

from pad4pi import rpi_gpio
import time


# Setup Keypad
KEYPAD = [
        ["1","2","3","A"],
        ["4","5","6","B"],
        ["7","8","9","C"],
        ["*","0","#","D"]
]

# same as calling: factory.create_4_by_4_keypad, still we put here fyi:
ROW_PINS = [16, 20, 21, 5] # BCM numbering; Board numbering is: 7,8,10,11 (see pinout.xyz/)
COL_PINS = [6, 13, 19, 26] # BCM numbering; Board numbering is: 12,13,15,16 (see pinout.xyz/)

factory = rpi_gpio.KeypadFactory()

# Try keypad = factory.create_4_by_3_keypad() or 
# Try keypad = factory.create_4_by_4_keypad() #for reasonable defaults
# or define your own:
keypad = factory.create_keypad(keypad=KEYPAD, row_pins=ROW_PINS, col_pins=COL_PINS)


class KeyStore:
    def __init__(self):
        #list to store them
        self.pressed_keys =''

    #function to clear string
    def clear_keys(self):
        self.pressed_keys = self.pressed_keys.replace(self.pressed_keys,'')

    def store_key(self,key):
        if key=='#':
            #printing the sequence of keys.
            print(self.pressed_keys)
            self.clear_keys()
        else:
            self.pressed_keys += key

keys = KeyStore()

# store_key will be called each time a keypad button is pressed
keypad.registerKeyPressHandler(keys.store_key)


try:
    while(True):
        time.sleep(0.2)
except:
    keypad.cleanup()