This is my wiring minus the Resistor Banks, toggles and LEDs.
I am loading this code:
Calibration.ino (2.0 KB)
I am using the serial monitor to command servo position. The serial monitor returns the position data, but the servos don't move. What am I doing wrong?
Show us a good image of your ‘actual’ wiring.
That's the only picture I have. The connections are:
MEGA PCA9865
+5v -> VCC
GND -> GND
SDA -> SDA
SCL -> SCL
MEGA Power is being provided by USB. A separate power supply is connected to the PCA9865 for servo power, and yes the negative side is connected to the common ground. I am currently using only servo output 0.
The Servo Motor is an SG90. The PWM light comes on on the PCA9865 when I command a move using the Serial Monitor.
The wiring is standard for connecting a MEGA and a PCA9865. And yes I have tried different motors, and the hookup has been verified multiple times. The SG90 is rated at 4.8 - 6V, I started at the low end at 5V and I moved up to high end. No difference.
Servo motors can't possibly be powered by a PCA9865.
The SG90 requires about 700 mA just to start moving. Use a separate power supply (e.g 4xAA battery pack) to power the servo, and connect all the grounds.
The GND on the Mega is connected to GND header pin on the PCA9865.
Hi,
Can you post a picture of your project?
What colour servo wires are connected to what 9865 servo pins?
Do you have a DMM?
Thanks.. Tom... 
Hi,
Have you soldered any of the A0 to A5 address pads?
Have you checked all your solder joints to the breakout PCB?
Thanks.. Tom...
What exactly are you sending via Serial and what values are being printed for 'pos'?
Steve
a+ or a- where a is the desired position from a center of 1500. The monitor returns the new position. Update: I am able to control a SERVO directly with the MEGA, so I believe there is something wrong with the calibration code used with the PCA9865. The power for the two boards is through the USB Port. I wonder if I should use a separate power source for them as well?
No solder joints, all jumpers.
The PCA9865 requires a separate power supply for the servos.
Hi,
You are using I2C, do you have a 4k7 resistor on each of SDA and SCL to 5V?
Tom...
The MEGA 2560 has internal 10Ks on both. It's the only board that has them.
I was asking if I should provide board power from a wallwart instead of from the USB?
The Arduino can be powered by USB.
VCC on the PCA9865 powered by the Arduino 5V pin.
The PCA9865 servo power terminals, powered by four AA batteries.
This is confirmed to work for the first two servo positions:
Impossible to screw up the connection.
/***************************************************
This is an example for our Adafruit 16-channel PWM & Servo driver
Servo test - this will drive 8 servos, one after the other on the
first 8 pins of the PCA9685
Pick one up today in the adafruit shop!
------> http://www.adafruit.com/products/815
These drivers use I2C to communicate, 2 pins are required to
interface.
Adafruit invests time and resources providing this open source code,
please support Adafruit and open-source hardware by purchasing
products from Adafruit!
Written by Limor Fried/Ladyada for Adafruit Industries.
BSD license, all text above must be included in any redistribution
****************************************************/
#include <Wire.h>
#include <Adafruit_PWMServoDriver.h>
// called this way, it uses the default address 0x40
Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver();
// you can also call it with a different address you want
//Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x41);
// you can also call it with a different address and I2C interface
//Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x40, Wire);
// Depending on your servo make, the pulse width min and max may vary, you
// want these to be as small/large as possible without hitting the hard stop
// for max range. You'll have to tweak them as necessary to match the servos you
// have!
#define SERVOMIN 150 // This is the 'minimum' pulse length count (out of 4096)
#define SERVOMAX 600 // This is the 'maximum' pulse length count (out of 4096)
#define USMIN 600 // This is the rounded 'minimum' microsecond length based on the minimum pulse of 150
#define USMAX 2400 // This is the rounded 'maximum' microsecond length based on the maximum pulse of 600
#define SERVO_FREQ 50 // Analog servos run at ~50 Hz updates
// our servo # counter
uint8_t servonum = 0;
uint8_t servonumMax = 1;
void setup() {
Serial.begin(9600);
Serial.println("First 2 channels, Servo test!");
pwm.begin();
/*
* In theory the internal oscillator (clock) is 25MHz but it really isn't
* that precise. You can 'calibrate' this by tweaking this number until
* you get the PWM update frequency you're expecting!
* The int.osc. for the PCA9685 chip is a range between about 23-27MHz and
* is used for calculating things like writeMicroseconds()
* Analog servos run at ~50 Hz updates, It is importaint to use an
* oscilloscope in setting the int.osc frequency for the I2C PCA9685 chip.
* 1) Attach the oscilloscope to one of the PWM signal pins and ground on
* the I2C PCA9685 chip you are setting the value for.
* 2) Adjust setOscillatorFrequency() until the PWM update frequency is the
* expected value (50Hz for most ESCs)
* Setting the value here is specific to each individual I2C PCA9685 chip and
* affects the calculations for the PWM update frequency.
* Failure to correctly set the int.osc value will cause unexpected PWM results
*/
pwm.setOscillatorFrequency(27000000);
pwm.setPWMFreq(SERVO_FREQ); // Analog servos run at ~50 Hz updates
delay(10);
}
// You can use this function if you'd like to set the pulse length in seconds
// e.g. setServoPulse(0, 0.001) is a ~1 millisecond pulse width. It's not precise!
void setServoPulse(uint8_t n, double pulse) {
double pulselength;
pulselength = 1000000; // 1,000,000 us per second
pulselength /= SERVO_FREQ; // Analog servos run at ~60 Hz updates
Serial.print(pulselength); Serial.println(" us per period");
pulselength /= 4096; // 12 bits of resolution
Serial.print(pulselength); Serial.println(" us per bit");
pulse *= 1000000; // convert input seconds to us
pulse /= pulselength;
Serial.println(pulse);
pwm.setPWM(n, 0, pulse);
}
void loop() {
// Drive each servo one at a time using setPWM()
Serial.println(servonum);
for (uint16_t pulselen = SERVOMIN; pulselen < SERVOMAX; pulselen++) {
pwm.setPWM(servonum, 0, pulselen);
}
delay(500);
for (uint16_t pulselen = SERVOMAX; pulselen > SERVOMIN; pulselen--) {
pwm.setPWM(servonum, 0, pulselen);
}
delay(500);
// Drive each servo one at a time using writeMicroseconds(), it's not precise due to calculation rounding!
// The writeMicroseconds() function is used to mimic the Arduino Servo library writeMicroseconds() behavior.
for (uint16_t microsec = USMIN; microsec < USMAX; microsec++) {
pwm.writeMicroseconds(servonum, microsec);
}
delay(500);
for (uint16_t microsec = USMAX; microsec > USMIN; microsec--) {
pwm.writeMicroseconds(servonum, microsec);
}
delay(500);
servonum++;
if (servonum > servonumMax) servonum = 0; // Testing the first 8 servo channels
}
Not bridged.
I don't code so I rely on code from others. All I want, for the moment is to use a MEGA and a PCA9865 to calibrate a single servo motor connected to the PCA. I want simple code that reports position and moves servo to a new position that I send with the serial monitor. Like this:
//www.elegoo.com
//2018.12.19
#include <Servo.h>
Servo myservo;
void setup(){
myservo.attach(9);
myservo.write(90);// move servos to center position -> 90°
}
void loop(){
myservo.write(90);// move servos to center position -> 90°
delay(500);
myservo.write(30);// move servos to center position -> 60°
delay(500);
myservo.write(90);// move servos to center position -> 90°
delay(500);
myservo.write(150);// move servos to center position -> 120°
delay(500);
}
except using I2c so I can do the same with a servo connected to the PCA9865. I also need a method to use the serial monitor to adjust position manually.
