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MD25 - Dual 12Volt 2.8Amp H Bridge Motor Drive

Serial mode documentation

(click here for I2C mode)

Automatic Speed regulation

By using feedback from the encoders the MD25 is able to dynamically increase power as required. If the required speed is not being

achieved, the MD25 will increase power to the motors until it reaches the desired rate or the motors reach there maximum

output. Speed regulation can be turned off with the use of the REGULATOR DISABLE command..

Automatic Motor Timeout

The MD25 will automatically stop the motors if there is no I2C communications within 2 seconds. This is to prevent your robot

running wild if the controller fails. The feature can be turned off with the DISABLE TIMEOUT command

Controlling the MD25

The MD25 is designed to operate with a TTL level serial bus (5v levels). Do not connect to RS232 directly, if you wish to connect to

RS232 it must be with the aid of a voltage level converter such as a ST232 or serial interface such as S13 which is available here:

www.robot-electronics.co.uk/acatalog/Serial_Interface.html

Commands

An easy to use command set provides all of the functions that the MD25 has to offer. The commands are sent with a sync byte of 0

at the start and then the command followed by any data bytes. The MD25 will then respond if the command is applicable.

command Name

Bytes sent to

MD25

Bytes

returned by

MD25

Description

0x21 GET SPEED 1 2 1 returns the current requested speed of motor 1

0x22 GET SPEED 2 2 1 returns the current requested speed of motor 2

0x23 GET ENCODER 1 2 4 motor 1 encoder count, 4 bytes returned high byte first (signed)

0x24 GET ENCODER 2 2 4 motor 2 encoder count, 4 bytes returned high byte first (signed)

0x25 GET ENCODERS 2 8 returns 8 bytes - encoder1 count, encoder2 count

0x26 GET VOLTS 2 1 returns the input battery voltage level

0x27 GET CURRENT 1 2 1 returns the current drawn by motor 1

0x28 GET CURRENT 2 2 1 returns the current drawn by motor 1

0x29 GET VERSION 2 1 returns the MD25 software version

0x2A GET ACCELERATION 2 1 returns the current acceleration level

0x2B GET MODE 2 1 returns the currently selected mode

0x2C GET VI 2 3 returns battery volts, motor1 current and then motor2 current

0x31 SET SPEED 1 3 0 set new speed1

0x32 SET SPEED 2 / TURN 3 0 set new speed2 or turn

0x33 SET ACCELERATION 3 0 set new acceleration

0x34 SET MODE 3 0 set the mode

0x35 RESET ENCODERS 2 0 zero both of the encoder counts

0x36 DISABLE REGULATOR 2 0 power output not changed by encoder feedback

0x37 ENABLE REGULATOR 2 0 power output is regulated by encoder feedback

0x38 DISABLE TIMEOUT 2 0 MD25 will continuously output with no regular commands

0x39 ENABLE TIMEOUT 2 0 MD25 output will stop after 2 seconds without communication

For example to read the battery voltage, send:

0x00 - sync byte

0x26 - READ VOLTS command

and the MD25 would respond with

0x77 - returned byte (119 decimal) 11.9v

Speed1

Depending on what mode you are in, this register can affect the speed of one motor or both motors. If you are in mode 0 or 1 it will

MD25 Serial Documentation http://www.robot-electronics.co.uk/htm/md25ser.htm

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Summary of content (3 pages)

PAGE 1
MD25 Serial Documentation http://www.robot-electronics.co.uk/htm/md25ser.htm MD25 - Dual 12Volt 2.8Amp H Bridge Motor Drive Serial mode documentation (click here for I2C mode) Automatic Speed regulation By using feedback from the encoders the MD25 is able to dynamically increase power as required. If the required speed is not being achieved, the MD25 will increase power to the motors until it reaches the desired rate or the motors reach there maximum output.
PAGE 2
MD25 Serial Documentation http://www.robot-electronics.co.uk/htm/md25ser.htm set the speed and direction of motor 1. The larger the number written to this register, the more power is applied to the motor. A mode of 2 or 3 will control the speed and direction of both motors (subject to effect of turn register). Speed2/Turn When in mode 0 or 1 this operates the speed and direction of motor 2. When in mode 2 or 3 Speed2 becomes a Turn value, and is combined with Speed1 to steer the device (see below).
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MD25 Serial Documentation 3 of 3 http://www.robot-electronics.co.uk/htm/md25ser.htm if new speed < current speed steps = (current speed - new speed) / acceleration register time = steps * 25ms For example : Acceleration register 1 2 3 5 (default) 10 Time/step Current speed New speed Steps Acceleration time 25ms 25ms 25ms 25ms 25ms 0 127 80 0 255 255 255 0 255 0 255 64 27 51 26 6.375s 1.6s 0.675s 1.275s 0.65s Mode The mode command changes the way the speed/turn values are used.