The PCA9685 is an I2C-bus controlled 16-channel LED controller optimized for LCD
Red/Green/Blue/Amber (RGBA) color backlighting applications. Each LED output has its
own 12-bit resolution (4096 steps) fixed frequency individual PWM controller that operates
at a programmable frequency from a typical of 40 Hz to 1000 Hz with a duty cycle that is
adjustable from 0 % to 100 % to allow the LED to be set to a specific brightness value.
All outputs are set to the same PWM frequency.

PCA9685 also has a built-in oscillator for the PWM control.
However, the frequency used for PWM control in the PCA9685 is adjustable from
about 40 Hz to 1000 Hz as compared to the typical 97.6 kHz frequency of the
PCA9635. This allows the use of PCA9685 with external power supply controllers. All
bits are set at the same frequency.

The PCA9685 has 4096 steps (12-bit PWM)          

1. J3 Mini USB 5V input for PWM V+ & GPIO output pin 10 V+                                    

    J2 2P Terminal Block 5V input for PWM V+ & GPIO output pin 10 V+

2. J1 Rs-Pi V2  GPIO output

3 JP13  DA0 ~ DA7   U14 Port A    . JP14 BA0 ~ BA7     U14 Port B

4. R64,R65,R66 ( for  U14 Address select  A0,A1,A2)

5. U14 SPI 23s17 -1  Port A,B            23s17 Datasheet

6. U15  uln2803 

7. U3 PCA9685 (PWM Port 0 ~ 15)       PCA9685 Data Sheet 

8. R10,R11,R12,R13,R14,R15( for U3 Address select A0,A1,A2,A3,A4,A5)