B4R Library rAdafruitPWMServoDriver
Brief
rAdafruitPWMServoDriver is an open-source library for Adafruit 16-channel PWM & Servo driver (PCA9685).
This library is wrapped from the library Adafruit_PWMServoDriver library.
Development Info
Files
The rAdafruitPWMServoDriver-NNN.zip archive contains the library and sample projects.
Install
Copy the rAdafruitPWMServoDriver library folder from the archive into your B4R Additional Libraries folder, keeping the folder structure intact.
Ensure the library Adafruit_PWMServoDriver library v2.3.2 is installed using the Arduino IDE libraries manager.
Wiring
Example wiring with 2 servos connected to PCA9685 channels 0 (first) and 15 (last).
PCA9685 = Arduino
SDA = A4 (green)
SCL = A5 (blue)
OE = Not used
GND = GND [common] (black)
VCC = 5V [logic] (orange)
V+ = External Power 5V (yellow)
PCA9685 = Servo 1 Channel 0
PWM = Signal
V+ = VCC
GND = GND
PCA9685 = Servo 2 Channel 15
PWM = Signal
V+ = VCC
GND = GND
External Power 5V 2A = PCA9685
1A for each servo.
V+ = VCC (orange)
GND = GND (black)
External Power 5V 2A = Arduino
GND = GND (black)
I2C Address
PCA9685 default address: 0x40 (change with A0-A5 jumpers)
Basic Example
Functions
Initialize()
Initialize with default I2C address (0x40).
Initialize2(addr As Byte)
Initialize with a custom I2C address.
Initialize3(Addr As byte, TwoWire &i2c)
Initialize with a custom I2C address and I2C bus instance.
Reset
Reset the device to default settings.
Sleep
Put the device into low-power sleep mode.
Wakeup
Wake the device from sleep mode.
SetExtClk(Byte prescale)
Use an external clock source.
prescale - The prescale value for the external clock.
SetPWMFreq(float freq)
Set PWM frequency for all channels.
freq - Frequency in Hz (typical for servos: 50–60 Hz).
SetOutputMode(bool totempole)
Configure output mode.
totempole - true for totem pole, false for open drain.
UInt GetPWM(channel As byte, off As Boolean)
Read PWM on/off values for a given channel.
channel - Channel channelber (0–15).
off - When true, returns the "off" value; otherwise, the "on" value.
Return - The raw PWM counter value.
Byte SetPWM(channel As Byte, on As UInt, off As UInt)
Set the on/off tick counts for a channel.
channel - Channel channelber (0–15).
on - Counter tick when signal goes high.
off - Counter tick when signal goes low.
Return - The last written "off" value.
SetPin(channel As Byte, val As UInt, invert As Boolean)
Set channel output value.
channel - Channel channelber (0–15).
val - PWM value (0–4095).
invert - When true, output is inverted.
Byte ReadPrescale
Read current prescale value.
WriteMicroseconds(channel As Byte, microseconds As UInt)
Write pulse length in microseconds to a channel.
channel - Channel channelber (0–15).
microseconds - Pulse width in µs.
SetOscillatorFrequency(freq As ULong)
Set the internal oscillator frequency.
freq - Frequency in Hz (e.g. 25,000,000).
GetOscillatorFrequency As ULong
Get the current oscillator frequency in Hz.
Custom Functions
DisablePWM(channel As Byte)
Disable PWM (servo free, no buzz) by setting pulse length to 0.
channel - Channel number (0–15).
SetLimits(channel As Byte, minAngle As Byte, maxAngle As Byte)
Set servo angle min / max limits on a given channel.
If not used, the defaults are 0°-180°.
channel - Channel number (0–15).
minangle - Minimum servo angle (clamped to ANGLE_MIN).
minangle - Maximum servo angle (clamped to ANGLE_MAX).
UInt SetAngle(channel As Byte, angle As UInt, disable As Boolean)
Set servo angle on a given channel.
channel - Channel channelber (0–15).
angle - Desired servo angle (clamped to servo min / max angle).
disable - Disable PWM (servo free, no buzz).
Return - Corresponding pulse length (out of 4096).
int GetAngle(channel As Byte)
Get servo angle on a given channel.
channel - Channel channelber (0–15).
Return - Current angle (0-180) or -1 if channel is invalid.
UInt AngleToPulse(angle As UInt)
Convert angle (0–180°) to PWM pulse length.
angle - Angle in degrees.
Return - Corresponding pulse length (out of 4096).
UInt PulseToAngle(microseconds As UInt)
Convert PWM pulse length to angle (0–180°).
microseconds - Pulse width in µs.
Return - Corresponding angle (0-180°). Not 100% accurate +/- 1°.
Constants
CHANNELS = 1 - Number of PWM channels (0-15),
PWM_FREQUENCY_DEFAULT = 6 - Default PWM frequency (Analog servos typically run at ~60 Hz).
SERVO_MIN = 15 - Minimum pulse length (out of 4096) corresponding to ~0°.
SERVO_MAX = 60 - Maximum pulse length (out of 4096) corresponding to ~180°.
ANGLE_MIN = 0 - Minimum angle 0°.
ANGLE_MAX = 18 - Maximum angle 180°.
MOVE_DELAY = 20 - Servo move delay in microseconds.
Notes & Tips
Servo noise/buzzing
This is expected, as the PCA9685 continuously refreshes PWM.
If it’s too loud then:
Credits
Adafruit Industries for the Adafruit_PWMServoDriver library.
Disclaimer
Original Library (Adafruit) - Copyright (c) 2012 Adafruit Industries. Licensed under the BSD 3-Clause License (see LICENSE file in the original repository).
License for this wrapper - Copyright © 2025 Robert W.B. Linn. Licensed unter the MIT License (see LICENSE file).
Brief
rAdafruitPWMServoDriver is an open-source library for Adafruit 16-channel PWM & Servo driver (PCA9685).
This library is wrapped from the library Adafruit_PWMServoDriver library.
Development Info
- Written in C++ (Arduino IDE 2.3.4 and the B4Rh2xml tool).
- Depends on the library Adafruit_PWMServoDriver.
- Tested with
- Hardware - Arduino UNO, Adafruit 16-Channel 12-bit PWM/Servo Driver - I2C interface - PCA9685, servos Power HD 1160A & Tower Pro Micro Servo 99
- Software - B4R 4.00 (64-bit), Adafruit_PWMServoDriver library v2.3.2.
- Notes
- Not all wrapped functions tested. Only those used in the examples.
- It is recommended to provide external power for the servos (1A per servo).
Files
The rAdafruitPWMServoDriver-NNN.zip archive contains the library and sample projects.
Install
Copy the rAdafruitPWMServoDriver library folder from the archive into your B4R Additional Libraries folder, keeping the folder structure intact.
Ensure the library Adafruit_PWMServoDriver library v2.3.2 is installed using the Arduino IDE libraries manager.
Wiring
Example wiring with 2 servos connected to PCA9685 channels 0 (first) and 15 (last).
PCA9685 = Arduino
SDA = A4 (green)
SCL = A5 (blue)
OE = Not used
GND = GND [common] (black)
VCC = 5V [logic] (orange)
V+ = External Power 5V (yellow)
PCA9685 = Servo 1 Channel 0
PWM = Signal
V+ = VCC
GND = GND
PCA9685 = Servo 2 Channel 15
PWM = Signal
V+ = VCC
GND = GND
External Power 5V 2A = PCA9685
1A for each servo.
V+ = VCC (orange)
GND = GND (black)
External Power 5V 2A = Arduino
GND = GND (black)
I2C Address
PCA9685 default address: 0x40 (change with A0-A5 jumpers)
Basic Example
B4X:
Sub Process_Globals
Private ANGLE_MIN_POS As UInt = 0
Private ANGLE_MID_POS As UInt = 90
Private ANGLE_MAX_POS As UInt = 180
Private SERVO_CHANNEL As Byte = 0 ' 0-15
Public Serial1 As Serial
Public PWMServoDriver As AdafruitPWMServoDriver
End Sub
Private Sub AppStart
Serial1.Initialize(115200)
Log(CRLF, "=======================================")
Log(CRLF, "[Main.AppStart] Initialize")
' Init the servo driver
PWMServoDriver.Initialize
' Set the pwm frequency - analog servos typically run at ~60 Hz
PWMServoDriver.SetPWMFreq(PWMServoDriver.PWM_FREQUENCY_DEFAULT)
' Set initial position for the servo at mid pos
PWMServoDriver.SetAngle(SERVO_CHANNEL, ANGLE_MID_POS, ANGLE_MIN_POS, ANGLE_MAX_POS, True)
Delay(2000)
' Move test positions
CallSubPlus("TestServo", 1, 5)
Log("[Main.AppStart] Done", CRLF)
End Sub
' Move servo to min, mid, max, mid positions.
Private Sub TestServo(Tag As Byte) 'ignore
Log("[TestServo] Start")
Dim angle As Int
angle = ANGLE_MIN_POS
PWMServoDriver.SetAngle(SERVO_CHANNEL, angle, ANGLE_MIN_POS, ANGLE_MAX_POS, True)
Log("[TestServo] set angle=",angle)
Delay(2000)
angle = ANGLE_MID_POS
PWMServoDriver.SetAngle(SERVO_CHANNEL, angle, ANGLE_MIN_POS, ANGLE_MAX_POS, True)
Log("[TestServo] set angle=",angle)
Delay(2000)
angle = ANGLE_MAX_POS
PWMServoDriver.SetAngle(SERVO_CHANNEL, angle, ANGLE_MIN_POS, ANGLE_MAX_POS, True)
Log("[TestServo] set angle=",angle)
Delay(2000)
angle = ANGLE_MID_POS
PWMServoDriver.SetAngle(SERVO_CHANNEL, angle, ANGLE_MIN_POS, ANGLE_MAX_POS, True)
Log("[TestServo] set angle=",angle)
Log("[TestServo] last angle=",PWMServoDriver.GetAngle(SERVO_CHANNEL))
Log("[TestServo] Done")
End SubFunctions
Initialize()
Initialize with default I2C address (0x40).
Initialize2(addr As Byte)
Initialize with a custom I2C address.
Initialize3(Addr As byte, TwoWire &i2c)
Initialize with a custom I2C address and I2C bus instance.
Reset
Reset the device to default settings.
Sleep
Put the device into low-power sleep mode.
Wakeup
Wake the device from sleep mode.
SetExtClk(Byte prescale)
Use an external clock source.
prescale - The prescale value for the external clock.
SetPWMFreq(float freq)
Set PWM frequency for all channels.
freq - Frequency in Hz (typical for servos: 50–60 Hz).
SetOutputMode(bool totempole)
Configure output mode.
totempole - true for totem pole, false for open drain.
UInt GetPWM(channel As byte, off As Boolean)
Read PWM on/off values for a given channel.
channel - Channel channelber (0–15).
off - When true, returns the "off" value; otherwise, the "on" value.
Return - The raw PWM counter value.
Byte SetPWM(channel As Byte, on As UInt, off As UInt)
Set the on/off tick counts for a channel.
channel - Channel channelber (0–15).
on - Counter tick when signal goes high.
off - Counter tick when signal goes low.
Return - The last written "off" value.
SetPin(channel As Byte, val As UInt, invert As Boolean)
Set channel output value.
channel - Channel channelber (0–15).
val - PWM value (0–4095).
invert - When true, output is inverted.
Byte ReadPrescale
Read current prescale value.
WriteMicroseconds(channel As Byte, microseconds As UInt)
Write pulse length in microseconds to a channel.
channel - Channel channelber (0–15).
microseconds - Pulse width in µs.
SetOscillatorFrequency(freq As ULong)
Set the internal oscillator frequency.
freq - Frequency in Hz (e.g. 25,000,000).
GetOscillatorFrequency As ULong
Get the current oscillator frequency in Hz.
Custom Functions
DisablePWM(channel As Byte)
Disable PWM (servo free, no buzz) by setting pulse length to 0.
channel - Channel number (0–15).
SetLimits(channel As Byte, minAngle As Byte, maxAngle As Byte)
Set servo angle min / max limits on a given channel.
If not used, the defaults are 0°-180°.
channel - Channel number (0–15).
minangle - Minimum servo angle (clamped to ANGLE_MIN).
minangle - Maximum servo angle (clamped to ANGLE_MAX).
UInt SetAngle(channel As Byte, angle As UInt, disable As Boolean)
Set servo angle on a given channel.
channel - Channel channelber (0–15).
angle - Desired servo angle (clamped to servo min / max angle).
disable - Disable PWM (servo free, no buzz).
Return - Corresponding pulse length (out of 4096).
int GetAngle(channel As Byte)
Get servo angle on a given channel.
channel - Channel channelber (0–15).
Return - Current angle (0-180) or -1 if channel is invalid.
UInt AngleToPulse(angle As UInt)
Convert angle (0–180°) to PWM pulse length.
angle - Angle in degrees.
Return - Corresponding pulse length (out of 4096).
UInt PulseToAngle(microseconds As UInt)
Convert PWM pulse length to angle (0–180°).
microseconds - Pulse width in µs.
Return - Corresponding angle (0-180°). Not 100% accurate +/- 1°.
Constants
CHANNELS = 1 - Number of PWM channels (0-15),
PWM_FREQUENCY_DEFAULT = 6 - Default PWM frequency (Analog servos typically run at ~60 Hz).
SERVO_MIN = 15 - Minimum pulse length (out of 4096) corresponding to ~0°.
SERVO_MAX = 60 - Maximum pulse length (out of 4096) corresponding to ~180°.
ANGLE_MIN = 0 - Minimum angle 0°.
ANGLE_MAX = 18 - Maximum angle 180°.
MOVE_DELAY = 20 - Servo move delay in microseconds.
Notes & Tips
Servo noise/buzzing
This is expected, as the PCA9685 continuously refreshes PWM.
If it’s too loud then:
- Use setPWMFreq(50) for standard analog servos.
- Make sure the MIN_PULSE/MAX_PULSE matches the servo specs.
- Optionally cut power (setPWM(channel, 0, 0)) if no need holding torque.
- 5V/2A is fine for 2 small servos.
- If adding more, servos can stall at 1A each, so upgrade the PSU accordingly.
- If the servos draw too much, the Arduino can reset.
- A decoupling capacitor (470–1000 µF) across PCA9685 V+ and GND helps stabilize.
- Use DisablePWM(channel) after moving the servo to its target if holding torque isn’t required.
- For applications needing torque (robot arms, RC steering), consider to keep PWM enabled.
Credits
Adafruit Industries for the Adafruit_PWMServoDriver library.
Disclaimer
- This project is developed for personal use only.
- All examples and code are provided as-is and should be used at your own risk.
- Any guidance provided as-is, without any guarantee or liability for errors, omissions, or wrong configurations.
- Always test thoroughly and exercise caution when connecting hardware components.
Original Library (Adafruit) - Copyright (c) 2012 Adafruit Industries. Licensed under the BSD 3-Clause License (see LICENSE file in the original repository).
License for this wrapper - Copyright © 2025 Robert W.B. Linn. Licensed unter the MIT License (see LICENSE file).
