Manual

5.d. 0x86 & 0x87: Motor M0 & M1 Coast

Command 0x86: Motor M0 Coast

Compact protocol: 0x86

Pololu protocol: 0xAA, device ID, 0x06

Command 0x87: Motor M1 Coast

Compact protocol: 0x87

Pololu protocol: 0xAA, device ID, 0x07

These commands will set the specified motor to coast by setting the motor outputs to high impedance, which lets

the motor turn freely. This is in contrast to setting the motor speed to 0, which sets the motor outputs to ground

and acts as a brake, resisting motor rotation.

You can see the effect of this yourself just by using your motor. First, with your motor disconnected from

anything, try rotating the output shaft and note how easily it turns. Then, short the two motor leads together and

try rotating the output shaft again. You should notice significantly more resistance while the leads are shorted

together. The motor-coast command is equivalent to disconnecting your motor and letting it turn freely while

setting the motor speed to zero is equivalent to shorting the motor leads together.

5.e. 0x88 - 0x8F: Set Motor Forward/Reverse

The qik can independently control two bidirectional brushed DC motors, driving each either forward or reverse

with either 7- or 8-bit speed resolution. In 7-bit mode, motor speed ranges from stopped to full speed as the

speed parameter ranges from 0 to 127. In 8-bit mode, motor speed ranges from stopped to full speed as the speed

parameter ranges from 0 – 255. The speed resolution can be controlled by the PWM configuration parameter (see

Section 5.c).

The motor direction convention used in this document is that “forward” corresponds to grounding the – pin while

PWMing the + pin between V

MOT

and ground. “Reverse” corresponds to grounding the + pin while PWMing the

– pin between V

MOT

and ground. Notions of “forward” and “reverse” are somewhat arbitrary. See Section 3.a for

information about motor and power connections.

Motor M0 Commands

Commands 0x88 – 0x8B apply to motor M0. In 8-bit mode, commands 0x89 and 0x8B will set the motor speed

to 128+motor speed; in 7-bit mode, command 0x89 is identical to command 0x88 and command 0x8B is identical

to command 0x8A.

For example, in 8-bit mode, the command packet 0x88, 0x7F will set motor M0 speed to 127 out of a maximum

of 255, which will result in the motor’s turning at half speed. The command packet 0x89, 0x7F will set motor M0

speed to 127+128 = 255, which will result in the motor’s turning at full speed. In 7-bit mode, both commands will

set motor M0 speed to 127 out of a maximum of 127, which will result in the motor’s turning at full speed.

Command 0x88: Motor M0 Forward

Compact protocol: 0x88, motor speed

Pololu protocol: 0xAA, device ID, 0x08, motor speed

Command 0x89: Motor M0 Forward (speed + 128; used in 8-bit mode)

Compact protocol: 0x89, motor speed

Pololu protocol: 0xAA, device ID, 0x09, motor speed

5. Serial Commands Page 18 of 24