Cytron Single 10- 45V, 40A Brushed DC Motor Controller : Data Sheet : Page 22

ROBOT . HEAD to TOE

Product User’s Manual – MDS40B

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8.4 SERIAL PACKETIZED MODE

In Packetized Serial mode, Enhanced SmartDrive40 is controlled by using the UART

interface. DIG1 pin is the UART Rx pin. DIG2, AN1 and AN2 pins are not used in this

mode. To control the motor, data sent to the driver must be in 4 bytes packet format which

includes a header, address, command and checksum. Up to 8 units of Enhanced

SmartDrive40 can be connected together to a single microcontroller UART Tx pin.

Besides that, the Enhanced SmartDrive40 also incorporates an Auto-Baud feature in

Packetized Serial mode. When the driver is first powered up, the host microcontroller must

send a header byte (Decimal 85 or hex 55) once to the driver. The driver will then calculate

the baud rate automatically based on this byte. After that, Enhanced SmartDrive40 is ready to

read full packet (4 bytes) and the baud rate cannot be changed without power recycle (power

off and on) or reset button.

NOTE:

1. When the driver is powered up and waiting for the header byte, the error LED will

blink and indicate that there is input error.

2. Enhanced SmartDrive40 may take up to 500ms to start up after power is applied.

Sending the header byte for auto baud during this time period may cause undesirable

results. Please allow one-second delay between applying power and sending the header

byte.

Packetized Serial mode is selected by setting SW1, SW2 and SW3 to 1 (Up). SW4 – SW6

are used to select the address.

Input Mode

SW1 - SW3

111

Packetized Serial Mode

UART Address

SW4 - SW6

000 - 111

0 - 7

0 - OFF 1 - ON X - Don’t Care

A packet consists of 4 bytes and the format is shown in the following table.

Byte

Name

Value (Decimal)

Description

1

Header

85

To indicate the start of packet.

2

Address

0 - 7

Used to identify the driver when multiple units are connected

together. The address bits (bit 2 - 0) must match the address

configured with the DIP switch.

3

Command

0 – 255

Value 127 stops the motor, 0 is full reverse and 255 is full

forward.

4

Checksum

0 – 255

The value for checksum must be the result of

Header + Address + Command