Micro Dot pHat - Brightness Control

Support
1

Hi Guys - How can I adjust the brightness of the matrix, I’ve looked at the fading text example and I can’t get my code to work?

from microdotphat import set_brightness, write_string, scroll, show, clear, set_decimal

  if BRIGHTNESS < MAX_BRIGHT:
    BRIGHTNESS = int(BRIGHTNESS + 10)
    set_brightness(BRIGHTNESS)
    message = "Br Up"
    clear()
    show_matrix(message)
    time.sleep(1)

even when I set a low (=5) brightness at the begining of my code it never changes at all ? The value is increasing as you would expect but has no effect - am I setting the value correctly?

2

What you’re doing looks right, although the uppercase format is generally used to denote constants in Python and not variables that changed.

Could you post your complete code?

3

Here we go, I’ve had another play and still can’t get it to adjust the brightness, for the life of me I can’t see what I’m doing wrong, basically I have a up/down buttons to adjust the brightness in this example - I know when it hits min/max it errors currently but this should impact the brightness setting ?:

  #!/usr/bin/env python
  import RPi.GPIO as GPIO #interacting with the GPIO  
  import time as time # keeping track of time
  from microdotphat import set_brightness, write_string, scroll, show, clear
  import threading
  import Queue 
  from threading import Thread  

 #========== set up statics ==========================================================
  global sw1_prev
  global sw2_next
  sw1_prev = False
  sw2_next = False
 #---------- GPIO SETUP---------------------------------------------------------------
 #Define GPIO Numbering Schema
 GPIO.setmode(GPIO.BCM)
 #Define individual GPIO Pins
 PIN_SW1_PREV = 20
 PIN_SW2_NEXT = 21
 #------------------------------------------------------------------------------------
def prev_callback(channel):
global sw1_prev
sw1_prev = True
def next_callback(channel):
global sw2_next
sw2_next = True
  #-------init Matrix------------------------------------------------------------------
  global max_bright
  global min_bright
  global cur_bright
  max_bright = 125
  min_bright = 5
  cur_bright = 100
  set_brightness(cur_bright)
  #------------------------------------------------------------------------------------
  GPIO.setup(PIN_SW1_PREV, GPIO.IN, pull_up_down=GPIO.PUD_UP)    # set 20 as input
  GPIO.setup(PIN_SW2_NEXT, GPIO.IN, pull_up_down=GPIO.PUD_UP)   # set 21 as input
  GPIO.add_event_detect(PIN_SW1_PREV, GPIO.FALLING, callback=prev_callback, bouncetime=300)
  GPIO.add_event_detect(PIN_SW2_NEXT, GPIO.FALLING, callback=next_callback, bouncetime=300)
  #===================================================================================
  #do stuff endlessly until ctrl+c etc
  #======
 def main():
  while True:
global sw1_prev
global sw2_next
global max_bright
global min_bright
global cur_bright
press = read_switches()

  # PREV button pressed
if(press == 1):
  print "Down"
  message = "Down"
  if cur_bright > min_bright:
    cur_bright = cur_bright -10
    set_brightness(cur_bright)
    clear()
    write_string(message, kerning = False)
    show()
    time.sleep(1)
    sw1_prev = False
  else:
    message = "Min!"
    write_string(message, kerning = False)
    clear()
    show()
    time.sleep(1)
    sw1_prev = False

  # NEXT button pressed
if(press == 2):
  print "Up"
  message = "Up"
  if cur_bright < max_bright:
    cur_bright = cur_bright +10
    set_brightness(cur_bright)
    clear()
    write_string(message, kerning = False)
    show()
    time.sleep(1)
    sw2_next = False
  else:
    message = "Max!"
    write_string(message, kerning = False)
    clear()
    show()
    time.sleep(1)
    sw2_next = False

  # BOTH buttons pressed together
if(press == 3):
  print "TBD"
  sw2_next = False
  delay_milliseconds(100)

  #==================================================================================
  def read_switches():
  # Debounce switches and look for two-button combo
  global sw1_prev
  global sw2_next
  delay_milliseconds(1)		
  if(sw1_prev and sw2_next):
    return 3
  if(sw2_next):
    return 2
   if(sw1_prev):
    return 1
return 0

def delay_milliseconds(milliseconds):
  seconds = milliseconds / float(1000)	# divide milliseconds by 1000 for seconds
  time.sleep(seconds)

  #=====
  if __name__ == "__main__":
    main()
4

… and in addition at a basic level the following code doesn’t set the brightness ?

   #!/usr/bin/python

   from microdotphat import set_brightness, write_string, scroll, show, clear, set_decimal
   from time import sleep

   # I would have thought a value of 1 would be very dim?
   set_brightness(1)

   while True:
    global message
    message = "Hello"
    clear()
    write_string(message, kerning=False)
    show()
    sleep(0.05)

If I add a value of say 500 it doesn’t error, so is it actually setting the value in my code ? Thanks for looking ! :)

5

Bump - Anyone got any ideas where I’m going wrong ?

6

I’m pretty sure brightness is intended to be a float between 0 and 1. I had a look at the lib and the boundaries are not enforced but the brightness parameter is multiplied by 127.

Anyhow, I’ll talk to @gadgetoid tomorrow but in the meantime it will work if you pass a value of 0.1 to dim the display, and I don’t suspect the next version of the lib will break your code if you assume 0 < brightness < 1

1 Like
7

yep that works - thanks lots, updated code that works:

 #!/usr/bin/python

  from microdotphat import set_brightness, write_string, scroll, show, clear, set_decimal
  from time import sleep

  # Value from 0.1 -> 1.0
  set_brightness(0.1)

  while True:
  global message
  message = "Hello"
  clear()
  write_string(message, kerning=False)
  show()
  sleep(0.05)