Build and Code Load the bots
Links and useful resources
Concept summary and connections
- Bots partial assembly, loading the code
- Checking state machine implementations
- Writing a pwm motor class
Lesson Content
Assembling what we have
We have the two updated designs mostly printed out (short some wheels and axles, which will print today). Let's get them assembled as much as possible, inserting bearings and attaching motors and stuff. Don't permanently attach any electronics yet - we may need to load these things up on a shop tool in order to make adjustments to holes for things to fit properly. Once it's all fitted together, move on to the next phase of updating your code for the new drive system.
Updating code for PWM-controlled DC motors
We need to update our bots so that they use the tb6612fng-motor-driver-setup. This will be different from the ContinuousServo class because we will be directly controlling the actual motor chip, and it'll take three pins: one for forward, one for reverse, and a PWM pin for speed. Here's the API it needs to present:
// File: motor_pwm.hpp
#ifndef MOTOR_PWM_HPP
#define MOTOR_PWM_HPP
/// This class implements a simple motor control scheme for a DC motor
// being driven by a TB6612fng dual h-bridge. You can configure the
// motor to be in normal or left-handed mode. In left-handed mode, it
// operates in reverse in order to allow you to use the same definition of
// forward for motors that are oriented in opposite directions (i.e. one on
// each side of a chassis to drive the wheels...).
//
// Speed ranges from -1 to 1 as a floating point value. The direction of rotation
// is the sign of the number, and the magnitude is mapped from [0...1] -> [0...255].
class MotorPWM {
public:
MotorPWM(int fwd_pin, int rev_pin, int speed_pwm_pin);
// The new speed ranges from [-1 ... 1], with negative numbers indicating reverse direction from positive.
void set_speed(float new_speed);
// Set this motor to be "left-handed", meaning that its rotation is reversed from normal
void set_left_handed(bool is_left_handed);
};
#endif
Remember that you'll use this code as the basic interface, but your actual class will need to have some member variables to keep track of speed, pin numbers, and direction, and you'll have to write the implementation for each method in a .cpp file.