Micropython, CardComputer - issue reading Keyboard

[MartynW]

Hi, I've sucessfully installed the most recent ESP32S3 build of Micropython on my M5Stack CardComputer. Due to it being a generic build, there are no specific device drivers included with the firmware; however, I've managed to get some integrated peripherals working, ie the LCD, sdCard.
The keyboard (schematic) in giving me some problems, its a pretty standard key matrix, the rows are provides using a 74hc138 3-8 line decoder, and the columns are 7 GPIOs. The outputs from the decoder are active low (datasheet), so I made the column pins inputs with pullups - doesnt work, needs pulldowns????
Reading the column pins whilst iterating through the 8 rows should allow the individual key detection, but although key presses yield a pin change it doesn't work as expected and column 2 is always high???

    from time import sleep_ms
    from machine import Pin

    '''
     M5Stack CardComputer Keyboard 
     74HC138 3 to 8 line decoder
    
     Decoder Pin   A2, A1, A0   ----\    Y6, Y5, Y4, Y3, Y2,  Y1,  Y0       
     GPIO Pin     G11, G9, G8   ----/    G7, G6, G5, G4, G3, G15, G13     
    '''
    
    class KeyBoard():
        def __init__(self):
            keyPins = [ ('C0', 13, Pin.IN, Pin.PULL_DOWN), ('C1', 15, Pin.IN, Pin.PULL_DOWN), ('C2', 3, Pin.IN, Pin.PULL_DOWN),
                        ('C3',  4, Pin.IN, Pin.PULL_DOWN), ('C4',  5, Pin.IN, Pin.PULL_DOWN), ('C5', 6, Pin.IN, Pin.PULL_DOWN),
                        ('C6',  7, Pin.IN, Pin.PULL_DOWN),
                        ('A0',  8, Pin.OUT, None), ('A1', 9, Pin.OUT, None), ('A2', 11, Pin.OUT, None) ]
    
            ap = dict()
            for (name, pin, direction, pull) in keyPins:
                self.pinMap[name] = Pin(pin, direction, pull) 

        def scan(self):
            for row in range(0,8):
                self.pinMap['A0'].value( row & 0b001 )
                self.pinMap['A1'].value( row & 0b010 >> 1 )
                self.pinMap['A2'].value( row & 0b100 >> 2 )
                sleep_ms(250)
                print(f'{row:04b}\t',end='')
                for col in ['C0', 'C1', 'C2', 'C3', 'C4', 'C5', 'C6']:
                    sleep_ms(0)
                    val = self.pinMap[col].value()
                    print(f'{val:01b} ', end='')
                print('')
            print('\n\n\n\n')
        
keyboard = KeyBoard()
while True:
    keyboard.scan()
    sleep_ms(500)

Any ideas of where I'm going wrong??

[felmue]

Hello @MartynW

I tried your code and changed two things to make it work:

• changed the inputs to pullups (as you already thought it should be) - the output matrix then is all 1s except for the button pressed.
• used some additional brackets for A1 and A2 to force the AND operation to happen first

            self.pinMap['A0'].value( row & 0b001 )
            self.pinMap['A1'].value( ( row & 0b010 ) >> 1 )
            self.pinMap['A2'].value( ( row & 0b100 ) >> 2 )

Full code:

from time import sleep_ms
from machine import Pin

    
class KeyBoard():
    def __init__(self):
      keyPins = [ ('C0', 13, Pin.IN, Pin.PULL_UP), ('C1', 15, Pin.IN, Pin.PULL_UP), ('C2', 3, Pin.IN, Pin.PULL_UP),
                  ('C3',  4, Pin.IN, Pin.PULL_UP), ('C4',  5, Pin.IN, Pin.PULL_UP), ('C5', 6, Pin.IN, Pin.PULL_UP),
                  ('C6',  7, Pin.IN, Pin.PULL_UP),
                  ('A0',  8, Pin.OUT, None), ('A1', 9, Pin.OUT, None), ('A2', 11, Pin.OUT, None) ]
    
      self.pinMap = dict()
      for (name, pin, direction, pull) in keyPins:
          self.pinMap[name] = Pin(pin, direction, pull) 

    def scan(self):
        for row in range(0,8):
            self.pinMap['A0'].value( row & 0b001 )
            self.pinMap['A1'].value( ( row & 0b010 ) >> 1 )
            self.pinMap['A2'].value( ( row & 0b100 ) >> 2 )
            sleep_ms(250)
            print(f'{row:04b}\t',end='')
            for col in ['C0', 'C1', 'C2', 'C3', 'C4', 'C5', 'C6']:
                sleep_ms(0)
                val = self.pinMap[col].value()
                print(f'{val:01b} ', end='')
            print('')
        print('\n\n\n\n')

    def scan2(self):
        for row in (7, 3, 6, 2, 5, 1, 4, 0):
            self.pinMap['A0'].value( row & 0b001 )
            self.pinMap['A1'].value( ( row & 0b010 ) >> 1 )
            self.pinMap['A2'].value( ( row & 0b100 ) >> 2 )
            sleep_ms(250)
            print(f'{row:04b}\t',end='')
            for col in ['C0', 'C1', 'C2', 'C3', 'C4', 'C5', 'C6']:
                sleep_ms(0)
                val = self.pinMap[col].value()
                print(f'{val:01b} ', end='')
            print('')
        print('\n\n\n\n')


keyboard = KeyBoard()
while True:
    keyboard.scan()
#    keyboard.scan2()
    sleep_ms(500)

BTW: I like your coding style with the pinMap etc. (Note: I am not very familiar with Micropython.)

Thanks
Felix

[MartynW]

Felix,

Thank you for the extra pair of eyes much appreciated, I got so obsessed with the PULL_UP/PULL_DOWN issue, I didn't even consider the processing order of the bitwise logic!! Many thanks.

Martyn

[felipeparaizo]

Hello @martynw, I've been trying for a while to get my CardComputer's screen to work with Micropython code. I want to display a simple "hello world," but I'm having trouble. Could you help me? Could you show your code for activating the screen and writing anything on it?

[thijsnl]

Hello MartynW

how do you use just the machine library. When I try this the m5stack gives an error.
When I use the m5stack lib I don't have any problems with this

[ajb2k3]

@felipeparaizo said in Micropython, CardComputer - issue reading Keyboard:

Hello @martynw, I've been trying for a while to get my CardComputer's screen to work with Micropython code. I want to display a simple "hello world," but I'm having trouble. Could you help me? Could you show your code for activating the screen and writing anything on it?

Have you added a driver to control the screen?

@thijsnl said in Micropython, CardComputer - issue reading Keyboard:

Hello MartynW

how do you use just the machine library. When I try this the m5stack gives an error.
When I use the m5stack lib I don't have any problems with this

What's is the error?

[felipeparaizo]

@ajb2k3 said in Micropython, CardComputer - issue reading Keyboard:

Você adicionou um driver para controlar a tela?

Não, qual seria esse driver ? como posso adicionar ?

[ajb2k3]

@felipeparaizo said in Micropython, CardComputer - issue reading Keyboard:

Não, qual seria esse driver ? como posso adicionar ?

Você precisa fazer upload do driver Micropython para a tela ST7789V2 no micropython usando thonny.