SparkFun Blocks for Intel® Edison - PWM
SFUptownMaker
CaseyTheRobot
HelloTechie
C++ Code Examples
We're assuming that you're using the Eclipse IDE as detailed in our Beyond Arduino tutorial. If you aren't, you'll need to read that tutorial to get up to speed.
Getting Started
Follow the instructions in the programming tutorial to create a new project named "SparkFun_PWM_Edison_Block_Example". Once you've created the project, open the project files on the disk (hint: you can find the path to the project by choosing "Properites" from the project menu), and copy the source files found in the SparkFun PWM Block for Edison C++ Library directly into the "src" directory.
Hardware Connection
For this example, we've got a sub-micro servo motor and a common anode RGB LED connected to the PWM block outputs. We've closed the VSYS->VIN jumper with a solder blob, so we're drawing power from the Edison's supply. For a larger servo motor or more LEDs, you should open that jumper, and connect an external supply to the VIN and GND pads at the end of the header.
Of course, you can connect any other device to the outputs here -- the PWM input to a motor driver, a buzzer, what have you. We just want to demonstrate the core capabilities of this block, which is to provide servo driving and visually normalized LED outputs.
Code
Everything you need to know is in the comments.
/****************************************************************************
* SparkFun_PWM_Edison_Block_Example.cpp
* Example code showing how to use the SparkFun PWM Edison Block
* Mike Hord @ SparkFun Electronics
* 9 June 2015
* https://github.com/sparkfun/SparkFun_PWM_Block_for_Edison_CPP_Library
*
* This file is a demonstration program showing the various functions that we've
* provided for working with the PCA9685 IC on the SparkFun PWM Edison Block.
* It uses an RGB LED and a small servo motor to show what the library can do.
*
* Resources:
* Requires Intel's MRAA framework. This can be downloaded from either the
* GitHub site (https://github.com/intel-iot-devkit/mraa) or in pre-built form
* from http://iotdk.intel.com/sdk/mraa-update/.
*
* Development environment specifics:
* Developed in the Intel iot-ide-dk Eclipse on Win 7 (v1.0.0.201502201135)
* Using lib-mraa v0.6.2
* On Edison poky-linux image build ww18-15
*
* This code is beerware; if you see me (or any other SparkFun employee) at the
* local, and you've found our code helpful, please buy us a round!
* ****************************************************************************/
#include "mraa.hpp"
#include "SparkFun_pca9685_Edison.h"
#include <iostream>
#include <unistd.h>
using namespace std;
// These channel definitions mirror the ones used in the PWM Block hookup guide.
#define SERVO 0
#define RED 2
#define GREEN 3
#define BLUE 4
// Uncomment one or both of these defines to enable the appropriate demo. Do
// note servo motors and LEDs are best used at different frequencies and
// polarities, so hooking both at once will give you bad results.
#define SERVO_DEMO
//#define LED_DEMO
// main() runs once and completes; there's no infinite loop here. Do note,
// though, that whatever settings you write to the PWM module will persist
// after the code has completed.
int main()
{
// Variables to be used elsewhere in the program.
uint16_t startTime, stopTime;
mraa::I2c* pwm_i2c; // We need to create an I2c object that we can pass to
// the pca9685 constructor. If you have more than one
// PCA9685 device on your bus (either by stacking more
// than one PWM block or by adding external boards via
// the I2C Expansion Block), you'll need to create a
// different I2c object for each one!
pwm_i2c = new mraa::I2c(1); // Tell the I2c object which bus it's on.
pca9685 pwm(pwm_i2c, 0x40); // 0x40 is the default address for the PCA9685.
// In general usage, you don't need to worry about getting or setting the
// mode registers or the prescaler register. I'm including these lines here
// just for example completeness purposes.
cout<<"Current mode register values: 0x"<<hex<<pwm.readModeRegisters()<<endl;
cout<<"Current prescaler: "<<dec<<static_cast<int16_t>(pwm.getPrescaler())<<endl;
pwm.setPrescaler(121);
// There are four generic functions allowing the user to change the start and
// stop times of the various channels. Generally, however, you shouldn't ever
// have to or want to use these, since there are more useful functions
// available which will be covered below.
pwm.setChlTime(RED, 0, 0);
pwm.setChlDuty(BLUE, 0);
pwm.setChlStart(GREEN, 0);
pwm.setChlStop(GREEN, 0);
pwm.setChlDuty(SERVO, 0);
#ifdef LED_DEMO
// When you call enableLEDMode(), you set the output to be approximately 400Hz
// and inverted. Thus, a 0 output will be a 100% high output. This allows us
// to use the output to drive common anode LEDs. See the tutorial for an
// example circuit.
pwm.enableLEDMode();
// Back to this, just so you can compare the settings in LED mode with the
// default (which is actually LED mode).
cout<<"Current mode register values: "<<hex<<pwm.readModeRegisters()<<endl;
cout<<"Current prescaler: "<<dec<<static_cast<int16_t>(pwm.getPrescaler())<<endl;
for (uint8_t i = 0; i <= 100; i++)
{
// Check and print the start and stop times for the RED channel, then set
// all three to one percentage point higher. You'll note that the start
// time is always 0, and that the stop times increase logarithmically. This
// lets us get a visually linear brightness out of the LEDs.
pwm.getChlTime(RED, &startTime, &stopTime);
cout<<"Start time: "<<dec<<startTime<<endl;
cout<<"Stop time: "<<dec<<stopTime<<endl;
pwm.setChlLEDPercent(BLUE, i);
pwm.setChlLEDPercent(GREEN, i);
pwm.setChlLEDPercent(RED, i);
usleep(100000);
}
sleep(4);
pwm.setChlTime(RED, 0, 0);
pwm.setChlTime(GREEN, 0, 0);
pwm.setChlTime(BLUE, 0, 0);
cout<<"LED demo complete!"<<endl;
#endif
#ifdef SERVO_DEMO
// We can set or get the minimum and maximum angles the angle set function
// expects to see.
int16_t servoMinAngle, servoMaxAngle;
pwm.getServoAngleLimits(&servoMinAngle, &servoMaxAngle);
cout<<"Current servo min angle: "<<dec<<servoMinAngle<<endl;
cout<<"Current servo max angle: "<<dec<<servoMaxAngle<<endl;
// Likewise, we can set the min and max of pulse widths. Each count here is
// about 4.5us, depending on the clock's accuracy.
uint16_t minServoPL, maxServoPL;
pwm.getServoAnglePulseLimits(&minServoPL, &maxServoPL);
cout<<"Current servo min pulse length: "<<dec<<minServoPL<<endl;
cout<<"Current servo max pulse length: "<<dec<<maxServoPL<<endl;
// These numbers are based on experimentation with SparkFun's generic
// sub-micro servo motor. You may find that they are too high or too low for
// your particular motor. The generic settings are fairly conservative and
// there is no need to use these functions unless you feel like you can get
// a wider range of motion by doing so.
servoMinAngle = 0;
servoMaxAngle = 160;
minServoPL = 108;
maxServoPL = 450;
pwm.setServoAnglePulseLimits(minServoPL, maxServoPL);
pwm.setServoAngleLimits(servoMinAngle, servoMaxAngle);
// enabling servo mode makes the output active high and sets the frequency to
// approximately 50Hz.
pwm.enableServoMode();
// For comparison against default values or LED mode values.
cout<<"Current mode register values: 0x"<<hex<<pwm.readModeRegisters()<<endl;
cout<<"Current prescaler: "<<dec<<static_cast<int16_t>(pwm.getPrescaler())<<endl;
// This steps through the full range of your servo's rotation. It also shows
// the start and stop time of the pulses, so you can see how those correspond
// to different positions.
for (int16_t i = servoMinAngle; i <= servoMaxAngle; i++)
{
pwm.getChlTime(SERVO, &startTime, &stopTime);
pwm.setChlAngle(SERVO, i);
cout<<"Start time: "<<dec<<startTime<<endl;
cout<<"Stop time: "<<dec<<stopTime<<endl;
usleep(100000);
}
cout<<"Servo demo complete!"<<endl;
#endif
return MRAA_SUCCESS;
}