Controlling LED's with PCA9685

Question

I have bought an Adafruit PCA9685 and completed the library installation, however, I have no clue of how to Program it. I want to base it on the following code I wrote:

import RPi.GPIO as GPIO
import time
import sys
from pubnub import Pubnub

GPIO.setmode(GPIO.BCM)

PIN_LIVING = 22
PIN_PORCH = 17
PIN_FIREPLACE = 27

GPIO.setup(PIN_LIVING,GPIO.OUT)
GPIO.setup(PIN_PORCH,GPIO.OUT)
GPIO.setup(PIN_FIREPLACE,GPIO.OUT)

FREQ = 100 # frequency in Hz
FIRE_FREQ = 30 #  flickering effect

# Duty Cycle (0 <= dc <=100)

living = GPIO.PWM(PIN_LIVING, FREQ)
living.start(0)

porch = GPIO.PWM(PIN_PORCH, FREQ)
porch.start(0)

fire = GPIO.PWM(PIN_FIREPLACE, FIRE_FREQ)
fire.start(0)

# PubNub

pubnub = Pubnub(publish_key='demo', subscribe_key='demo')

channel = 'pi-house'

def _callback(m, channel):
    print(m)

    dc = m['brightness'] *10

    if m['item'] == 'light-living':
        living.ChangeDutyCycle(dc)

    elif m['item'] == 'light-porch':
        porch.ChangeDutyCycle(dc)

    elif m['item'] == 'fireplace':
        fire.ChangeDutyCycle(dc)

def _error(m):
  print(m)

pubnub.subscribe(channels='pi-house', callback=_callback, error=_error)

try:
    while 1:
        pass
except KeyboardInterrupt:
    GPIO.cleanup()
    sys.exit(1)

I dont know if on this its similar. I bought it because I wanted to be able to control more LED's with PWM from the Raspberry pi. I looked into it and found all kinds of weird commands and terms specific to this Chip.

Thanks!

Answer 1

First, If you look at page 29 of the data sheet (fig. 15) it shows that for Direct LED connection, you need to connect your LEDs inverted. ie connect the ground of the LED to the PWM line on the PCA9685 and the positive of the LED to the V+

Code is pretty simple (below is for an Arduino) And you use the function pwm.setPWM(uint8_t num, uint16_t on, uint16_t off) to turn the LEDs on and off and to different levels of brightness.

#include <Wire.h>
#include <Adafruit_PWMServoDriver.h>

Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver();

void setup()
{
Serial.begin(9600);

pwm.begin();
pwm.setPWMFreq(1600);  //This is the maximum PWM frequency

pwm.setPWM(1,0,4095); //this turns on the LED connected to channel one (I suspect the only line you're really looking for)
}

Hope that answers your question!

Answer 2

See below how to do this in python

import Adafruit_PCA9685
pwm = Adafruit_PCA9685.PCA9685()

pwm.set_pwm_freq(60)

# Demo using LED on Channel 12 of the PCA9685
# Wire up the LED  on  Channel 12 such that 
#    Shortleg of LED goes to GND and
#    Long leg goes to PWM pin on channel 12

pwm.set_pwm(12,0,4095)   # Full bright
time.sleep(5)

pwm.set_pwm(12,1024,3072) # half bright
time.sleep(5)

pwm.set_pwm(12,0,0)  #off
time.sleep(5)