CommandStation-EX/PWMServoDriver.cpp

/*!
 *  @file PWMServoDriver.cpp
 *
 *  @mainpage Adafruit 16-channel PWM & Servo driver, based on Adafruit_PWMServoDriver
 *
 *  @section intro_sec Introduction
 *
 *  This is a library for the 16-channel PWM & Servo driver.
 *
 *  Designed specifically to work with the Adafruit PWM & Servo driver.
 *  This class contains a very small subset of the Adafruit version which
 *  is relevant to driving simple servos at 50Hz through a number of chained 
 *  servo driver boards (ie servos 0-15 on board 0x40, 16-31 on board 0x41 etc.)
 *  
 *  @section author Author
 *  Chris Harlow (TPL) 
 *  original by Limor Fried/Ladyada (Adafruit Industries).
 *
 *  @section license License
 *
 *  BSD license, all text above must be included in any redistribution
 */
#include <Arduino.h>
#include <Wire.h>
#include "PWMServoDriver.h"
#define DIAG_ENABLED true
#include "DIAG.h"


// REGISTER ADDRESSES
const byte PCA9685_MODE1=0x00;      // Mode Register 
const byte PCA9685_FIRST_SERVO=0x06;  /** low byte first servo register ON*/
const byte PCA9685_PRESCALE=0xFE;     /** Prescale register for PWM output frequency */
// MODE1 bits
const byte MODE1_SLEEP=0x10;   /**< Low power mode. Oscillator off */
const byte MODE1_AI=0x20;      /**< Auto-Increment enabled */
const byte MODE1_RESTART=0x80; /**< Restart enabled */

const byte PCA9685_I2C_ADDRESS=0x40;      /** First PCA9685 I2C Slave Address */
const float FREQUENCY_OSCILLATOR=25000000.0; /** Accurate enough for our purposes  */
const uint8_t PRESCALE_50HZ = (uint8_t)(((FREQUENCY_OSCILLATOR / (50.0 * 4096.0)) + 0.5) - 1);
  
/*!
 *  @brief  Sets the PWM frequency for a chip to 50Hz for servos
 */

byte PWMServoDriver::setupFlags=0;  // boards that have been initialised

void PWMServoDriver::setup(int board) {
  if (board>3 || setupFlags & (1<<board)) return;
  Wire.begin();
  uint8_t i2caddr=PCA9685_I2C_ADDRESS + board;
  //DIAG(F("\nPWMServoDriver::setup %x prescale=%d"),i2caddr,PRESCALE_50HZ); 
  writeRegister(i2caddr,PCA9685_MODE1, MODE1_SLEEP | MODE1_AI);    
  writeRegister(i2caddr,PCA9685_PRESCALE, PRESCALE_50HZ);  
  writeRegister(i2caddr,PCA9685_MODE1,MODE1_AI);
  writeRegister(i2caddr,PCA9685_MODE1,  MODE1_RESTART | MODE1_AI);
  setupFlags|=1<<board;
}

/*!
 *  @brief  Sets the PWM output to a servo
 */
void PWMServoDriver::setServo(short servoNum, uint16_t value) {
  //DIAG(F("\nsetServo %d %d\n"),servoNum,value);
  int board=servoNum/16; 
  int pin=servoNum%16;
  
  if (board<0 | board>3) return; // safe dropout
  setup(board); // in case not already done
  
  Wire.beginTransmission(PCA9685_I2C_ADDRESS + board);
  Wire.write(PCA9685_FIRST_SERVO + 4 * pin); // 4 registers per pin
  Wire.write(0);
  Wire.write(0);
  Wire.write(value);
  Wire.write(value >> 8);
  Wire.endTransmission();
}

void PWMServoDriver::writeRegister(uint8_t i2caddr,uint8_t hardwareRegister, uint8_t d) {
  Wire.beginTransmission(i2caddr);
  Wire.write(hardwareRegister);
  Wire.write(d);
  Wire.endTransmission();
  delay(5); // allow registers to settle before continuing
}