Introduction: Digilent MRK + Line-Following Robot Assembly Instructions


The Digilent Line-Following Motor Robot Kit (MRK+Line) provides the perfect starting point for those new to robotics, but has the power to be used for advanced designs and applications as well. The MRK+Line pairs our powerful chipKIT Pro MX4 microcontroller development board with a rugged steel platform and all the motors, wheels, sensors, and other parts needed to build a complete robot.

To read more about the Digilent Robot kits, check out this post.

This demonstrates a simple design that will get your MRK+Line up and running, using its four IROS sensors to follow a dark line on a lightly colored surface. Using your MRK+Line’s powerful chipKIT Pro MX4 microcontroller, you’ll be able to add all sorts of functionality to your robot. Add some of our extensive line of peripheral modules (Pmods™) and you can design almost anything!

Your chipKIT Pro MX4 can be programmed with either Microchip MPLAB® IDE or chipKIT™ MPIDE. Microchip MPLAB IDE can be downloaded for free from chipKIT MPIDE can be downloaded for free from

The demo project used in this design can be downloaded from the Line-Following Motor Robot Kit product page at For more information on programming the chipKIT Pro MX4 with MPLAB or MPIDE, see the chipKIT Pro MX4 Reference Manual, available from the chipKIT Pro MX4 product page at

Included parts:

• chipKIT Pro MX4

• PmodLS1 with 6-pin cable

• Two PmodHB5 2A H-bridge motor amplifiers with attachment clips and 6-pin cables

• Four IROS sensors

• metal standoffs for microcontroller board

• rugged metal platform with holes on 1/2" center

• two 1/19 ratio motor/gearbox drives with ABS plastic wheels (1/53 gear ratio motors also available)

• rugged plastic wheels and drag button

• rugged metal motor mount

• all wiring and assembly hardware included

• angled bracket

• 4” Velcro mounting strip

• 6” 6-pin cable

Functional Description

The rugged steel components have holes on 1/2" centers so Digilent circuit boards and other vendors’ products can be easily attached.

MRK+Line Reference Manual page 2 of 11 Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.

The following tools are recommended for robot assembly:

  • regular and small Phillips head screwdrivers
  • adjustable wrench
  • pliers
  • wire strippers
  • scissors
  • hot glue (optional)

Helpful Hints:

- make sure that you tighten all the screws as much as possible, once it is put together you will have to take it apart to tighten some of the screws.

- Once the sensors are placed correctly you can use hot glue rather than Velcro for more stable sensors.

Step 1:

Place the motor mount on the third row of holes from one side of the platform. Attach it with two screws from one of the HW #1 Hardware Kits.

Step 2:

Take out the two HW#2 Hardware Kits and attach the Pmod clips to the platform using the holes that are in the same row as those you just used to attach the motor mount, but four holes from the opposite edge.

Step 3:

Flip over the platform and arrange it so the side with the motor mount is closest to you. Attach the third Pmod clip using the hole that is two away from the right-hand screw attaching the motor mount.

Step 4:

Flip over the platform. Attach the battery holder to the platform using the shorter Velcro strip, placing the shorter side against the motor mount.

Step 5:

Attach the drag button on the edge of the platform, next to the battery holder.

Step 6:

Attach the angled bracket to the front of the platform.

Step 7:

Flip over the Platform and put the side with the motor mount closest to you. Mount the chipKIT Pro MX4 on the top left corner using the Stand-off Hardware kit.

Step 8:

Flip over the platform. Attach the motors to the motor mount with the miniature screws.

Step 9:

Strip 3/8” of insulation from both ends of all four 22-gauge power wires.

Step 10:

Connect the motors to the PmodHB5s.

Step 11:

Attach the two PmodHB5s to the Pmod clips on the bottom of the platform.

Step 12:

Route power wires from eachPmod HB5 to the J18 power connector on the chipKIT Pro MX4 board, noting ground and voltage connections.

Step 13:

Connect the two PmodHB5 modules to port JD on the chipKIT Pro MX4 board using the two 6-pin cables. Using the PmodHB5s, connect the left motor to the bottom row of JD, and the right motor to the top row of JD. Use the marker on the cable connector to ensure that pin placements are in alignment when connecting the boards. See the pictures below.

Step 14:

Get the two wheels and the rubber traction bands. Stretch the rubber band around the outxide of the wheel. Attach the wheels to the motors.

If you are extra serious about your robot you can purchase better tires at,403,1002&Prod=MT-STICKY-TIRES. They provide more traction and stay on way better than the tires that come in the kit.

Step 15:

Cut one side of the Velcro in half and the other in quarters.

Step 16:

Mount the two halves of the Velcro onto the angled bracket and the quarters on the back of the sensors as shown below.

Step 17:

Mount the PmodLS1 in the last Pmod clip and plug in the sensors paying close attention to the orientation of the colors.

Step 18:

Mount the sensors with the Velcro making sure that the order of the sensors on the PmodLS1 match the order of the sensors on the angled bracket.

It is easiest to use the sensors if they are as close to the ground as possible without dragging. Then you can adjust the sensitivity on the PmodLS1 as necessary.

Step 19:

Attach the PmodLS1 to the Pmod clip, and then connect the PmodLS1 to the top row of the Pmod header JJ using the 6-pin cable. Take care that the pins are connected correctly. The flower-like symbol should only be viewable on one end of the cable. Please see the pictures below.

Step 20:

When you are ready to power the board, add four AA batteries to the battery pack, and connect the power cable from the battery pack to the J14 battery power connector on the chipKIT Pro MX4 board.

Step 21:

Compare your chipKIT Pro MX4 board to the picture below. Note that the blue shorts are attached to each jumper as shown. You can now use MPLAB or MPIDE to program the LineFollowingMRK demo project to the board.

Again, this demo can be downloaded from the Line-Following Motor Robot Kit product page at Note that running the reference design requires that the power select mode jumper J12 be shorted to External Power (EXT).

Step 22:

Add your own modifications to the robot!

Step 23:

Once the board has been programmed with the reference design, place the robot on a lightly colored (preferably white) surface with a black line between the two middle sensors. Turn the board on and press button 2 (BTN2) to cause the motors to turn and watch the robot follow the black line. Press button 1 (BTN1) to stop the robot.



Nice job, cool robot!

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