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6. Using the Serial Interface

The Simple Motor Controller has two serial interfaces that allow you to send commands and receive responses from

the controller. The commands and responses are represented as a series of bytes [http://simple.wikipedia.org/wiki/Byte].

Serial commands let you set the speed of the motor when the Input Mode is Serial/USB. In any Input Mode, serial

commands let you request information about the motor controller’s state and monitor the RC and Analog channel

inputs. The serial commands can come from a TTL serial source, such as a microcontroller, transmitted to the motor

controller’s RX pin, or they can come via USB transmitted to the controller’s virtual COM port. The Simple Motor

Controller treats the two command sources independently and can simultaneously process commands from both

sources.

The Simple Motor Controller can also be controlled using its native USB interface (see Section 7).

COM Port

The Simple Motor Controller installs as two devices, one of which is a virtual serial (COM) command port (see

Section 3.1 for driver installation instructions). You can identify the COM port number by looking in your computer’s

Device Manager:

Windows Vista or Windows 7 device manager showing a Simple Motor Controller.

In Linux, the COM port name will be something like /dev/ttyACM0. In Mac OS X 10.7 or later the COM port name

will be something like /dev/cu.usbmodemfa121.

You can use a terminal program or computer software to send commands to this virtual serial port over USB. Most

common programming languages have libraries for sending serial data (e.g. Visual C# has a SerialPort class), which

makes it easy to write a custom computer program to control the Simple Motor Controller. See Section 6.7 for code

examples. The baud rate settings do not matter when communicating through the virtual COM port.

TTL Serial

The Simple Motor Controller’s serial receive line, RX, can receive bytes from a TTL serial source, such as a

microcontroller, which allows for integration into embedded systems. The RX line expects a logic-level (0 to 2–5 V,

or “TTL”), non-inverted serial signal.

6. Using the Serial Interface Page 56 of 101

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Pololu Simple Manual de usuario Pagina 56