# University Programs Knowledge Base

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# University Programs Knowledge Base

## MCU 101: How does a DC Motor work?

How does a DC Motor work? The DC motor is a machine that transforms electric energy into mechanical energy in form of rotation. Its movement is produced by the physical behavior of electromagnetism. DC motors have inductors inside, which produce the magnetic field used to generate movement. But how does this magnetic field changes if DC current is being used? An electromagnet, which is a piece of iron wrapped with a wire coil that has voltage applied in its terminals. If two fixed magnets are added in both sides of this electromagnet, the repulsive and attractive forces will produce a torque. Then, there are two problems to solve: feeding the current to the rotating electromagnet without the wires getting twisted, and changing the direction of the current at the appropriate time. Both of these problems are solved using two devices: a split-ring commutator, and a pair of brushes. As it can be seen, the commutator has two segments which are connected to each terminal of the electromagnet, besides the two arrows are the brushes which apply electric current to the rotary electromagnet. In real DC motors it can be found three slots instead of two and two brushes. This way, as the electromagnet is moving its polarity is changing and the shaft may keep rotating. Even if it is simple and sounds that it will work great there are some issues which make these motors energy inefficient and mechanically unstable, the principal problem is due to the timing between each polarity inversion. Since polarity in the electromagnet is changed mechanically, at some velocities polarity is changing too soon, which result in reverse impulses and sometimes in changing too late, generating instantaneous “stops” in rotation. Whatever the case, these issues produce current peaks and mechanical instability. How a DC motor can be controlled? DC motors have only two terminals. If you apply a voltage to these terminals the motor will run, if you invert the terminals position the motor will change its direction. If the motor is running and you suddenly disconnect both terminals the motor will keep rotating but slowing down until stopping. Finally if the motor is running and you suddenly short-circuit both terminals the motor will stop. So there is not a third wire to control a DC motor, but knowing the previous behaviors it can be designed a way to control it, and the solution is an H-bridge. Look at the last evolution of the DC Motor above, you can observe that there are four gates and a motor connected between them. This is the simplest H-bridge, where the four gates represent for transistors. By manipulating these gates and connecting the upper and lower terminals to a voltage supply, you can control the motor in all the behaviors as below. Things to Consider When Using Motors With the Motor and Line scan Camera hooked up to the same board there is a significant problem with noise. The higher you turn the PWM on your drive motors the noise produced and the worse the data will appear from the camera. TO significantly reduce this noise you can simply solder an inductor directly across the 2 drive motors. This will allow you to increase the speed of the car without significantly affecting the data you receive back from the camera.

## Kinetis K40

32-bit Kinetis MCUs represent the most scalable portfolio of ARM® Cortex™-M4 MCUs in the industry. Enabled by innovative 90nm Thin Film Storage (TFS) flash technology with unique FlexMemory (configurable embedded EEPROM), Kinetis features the latest low-power innovations and high performance, high precision mixed-signal capability. For the Freescale Cup Challenge, we have provided several tutorials, example code and projects based on the twr-k40x256-kit. This board is part of the Freescale tower-system, a modular, reusable development platform that allows engineers to quickly prototype new designs. The K40 chip is a 144 pin package with 512KB of Flash, 245Kb of Program Flash, 4KB of EEProm, and 64KB of SRAM . Important Documents: Reference Manual Besides the Reference manual and the Datasheet, the most useful document for learning to program the K40 chip is the Kinetis Peripheral Module Quick Reference Data sheet Errata External Links Freescale's Kinetis K40 Product Page

## Microcontrollers

A microcontroller includes a microprocessor (CPU) as well as a number of other components like RAM, flash and EEPROM to store your programs and constants. While a microprocessor requires external devices to control things like input/output, or timers to implement periodic tasks, and digital to analog converters, a microcontroller is all inclusive. Contrast this all-in-one approach with a typical personal computer which contains an INTEL or AMD CPU, as well as separate chips for RAM, a separate video card, a dedicated hard drive, silicon chips or PCI circuit boards to enable the processor to access USB, serial and video card signals Microcontroller pins are general purpose, whereas CPU pins are specific. This means that each pin is tied to a multiplexer which you must set to choose the particular use for the pin. For example, in a microcontroller, one pin pin might be re-purposed for the following tasks 1. The output of a timer 2. Send a signal to a motor 3. Receive an input from a sensor or analog device Basic Concepts Covered Thus far: Blink an LED - overview of GPIO and setting up the microcontroller Drive a Motor - using the Timer and PWM modules of the microcontroller Turn a Servo - More details on using timer modules and PWM to control a servo Obtain Data from the Line Scan Camera - ADC Setup and GPIO Bit Blasting to create clock and pulse signals controlling the line scan camera I2C tutorial - Using I 2 C to communicate with various sensors using the K40 Button - An overview of how to implement a simple button Additional Concepts we would like to add to the Wiki: Timer Modules PWM watchdog-timer memory

## DIY MCU Board Mounts

Depending on which MCU Devlopment board you have chosen, you will need to figure out a way to mount this to the chassis. I have seen everything from cardboard, to aluminum, to wood. Below is a template complete with CAD drawings to mount the Qorivva TRK-MPC5604B board and the Motor Board onto the chassis. We use plexiglass for ours, but any other millable material is appropriate. The large hole in the middle is for cables from the servo. We attach the board to the car using the plastic standoffs (you will need them 55 mm long, so in our case, we used the combination of 40 + 15 mm) - see an example (SOS code 10260). To attach both the processor and interface boards the simillar 5mm plastic standoffs were used. Preview (.pdf) CAD file (.dxf)

## Batteries

Overview Please check your local rules to confirm allowable voltage, battery chemistry and ampere-hour as these differ by region. This article is NOT a substitute for the rules. Batteries (nor Charger) are not included in the Freescale Cup kit due to global shipping complexities. Batteries can be hazardous if not stored, used and/or disposed of properly. Battery Specifications Tamiya Connector 7.2 Volts Less than or equal to 3000mAh (Check your Rules!) NiCd or NiMH Needs to have a Tamyia connector Sources of purchase   This format battery is fairly common in the radio controlled toy industry. Start your search at any local electronics store where Radio controlled toy's are sold. Retail Sources: Radio Shack (USA) - http://www.radioshack.com/product/index.jsp?productId=4273066 Fry's (USA) - http://www.frys.com/product/6468002?site=sr:SEARCH:MAIN_RSLT_PG   Online Sources All-Battery.com http://www.all-battery.com/nicd72v2400mahhighpowerbatterypackforrccarswithtamiyaconnector.aspx http://www.all-battery.com/Tenergy7.2V3000mAhRCCarNiMHBatteryPackwithCharger-91103.aspx Europe: use Conrad online stores Conrad energy NiMH Sub-C Racingpack 7.2 V / 2400 mAh Stecksystem Tamiya-Stecker im Conrad Online Shop | 206026 (Conrad Germany but same available form other sources)

## Camera Mounts

Option #1 Camera Mount Designed by Eli Hughes of WaveNumber LLC. You can order these parts through Shapeway.com which 3D prints on demand. You can choose from all sorts of materials depending on how much you want to spend. Camera Mount Option #2 To attach the camera we found useful to prepare two metal L-shaped pieces made from aluminium. With the help of black plastic distance posts (already available in the kit) and these metal stands, you may freely change the position of the camera over the surface. You may use following files to cut the required shapes (drawing was made using the QCad program): Preview (.pdf) CAD file (.dxf)

## Freescale Cup Motor Driver Board

For details on how to use the Motors, visit theDC Motor Tutorial Images Boards before 2013 Current Board Rev. 0 Rev. 1 T echnical Details Revision 1 (Schematics, design files, sample code, instructional videos) Revision 0 (Schematics) H-Bridge Specifications Freescale MC33931 Datasheet Pro Tips: #1 - Electro-Magnetic Interfence (EMI) This has been mitigated in the rev. 1 board. In many cases the dc drive motors give off much EM interference causing poor data from the camera, and decreasing the servo motor performance substantially. In most cases around a PWM value of 20-25 duty cycle at the drive motors, caused detrimental problems. This problem was remedied in two ways, (1) connecting capacitors between the motor leads, the closer to the drive motor the better; (2) There is a way to connect the camera directly to the kwikstik and bypass the motor board. #2 - Rev. 0 Board workaround to Enable Braking This has been fixed in the rev. 1 board. In order to go forward AND backwards, you have to have control over IN1 and IN2 (see table below). If you look at the schematic, you can see that IN1 is directly connected to GND. In order to enable breaking you need to lift pin 43, solder a wire to it and control it properly. Tutorials General Tutorial on the DC Motor Control Qorivva: DC Motor Tutorial Kinetis Tower: DC Motor Tutorial Design evolution of motor board prior to 2010 - Freescale Cup Cars utilized the MC33932EVB 2010~2012 - Freescale Cup teams migrated to the current Interface/Motor board featuring Dual H-Bridges [Not manufactured] Tower and Trak Compatible Interface/Motor Control Board (Design files if you want to make one!) 2013+ - FRDM-KL25Z shield

## Line Scan Camera Board

The Freescale linescan camera is based upon the TSL1401CL sensor from TAOS Inc. Design Files Schematic & 3D Render (Courtesy of eli_hughes) Images (Lens removed) Freescale Linescan Camera Specifications 128-pixel linear image sensor (TSL1401CL) Focusable imaging lens 5-pin physical interface on PCB on .100" grid Simple three-pin MCU interface with analog pixel output Lens: 7.9mm focal length, f2.4 fixed aperture, manual focus, 12mm x 0.5mm thread Exposure Time: 267µS to 68mS Resolution: 128 pixels Built-In amplifier stage to improve white/black differentiation. The lense used on the board: Alaud Optical     8.0mm f.l. Lens w/IR filter = Part Num: AB0825C        M12x.05 Lens Holder = #9 or #10 Useful links AMS TSL1401 Product Page Line Scan Camera Use Freescale App Note: Line Scan Camera

## Tower TWR-K40X256-KIT (Kinetis K40)

The TWR-K40X256 Kit is a Freescale evaluation board powered by the Kinetis K40 microcontroller. The Kinetis microcontroller family is a set of 32 bit ARM Cortex M4 chips which feature flexible storage, lower power usage, high performance and optional Floating Point Unit with many useful peripherals. For more information on the Kinetis family see Freescale's Kinetis website. The Tower System is a prototyping platform with interchangeable and reusable modules along with open source design files. TWR K40X256 Hardware Setup There are several main hardware configuration steps. After installing the battery, once the USB cable has been connected between the evaluation board and PC, it may be necessary to update the chip firmware which requires moving a jumper pin on the evaluation board. TWR K40X246 Hardware Setup Instructions Board Specific Tutorials K40 Blink LED K40 Drive DC Motor K40 Drive Servo Motor K40 Line Scan Camera Board Tips The TWR-K40X256 features a socket that can accept a variety of different Tower Plug-in modules featuring sensors, RF transceivers, and more. The General Purpose TWRPI socket provides access to I2C, SPI, IRQs, GPIOs, timers, analog conversion signals, TWRPI ID signals, reset, and voltage supplies. The pinout for the TWRPI Socket is defined in Table 3 of the TWR-K40X256 User's Manual, but the user manual does not describe how to order a connector A Samtec connector, part number: SFC-110-T2-L-D-A is the proper female mating connector for the TWR-K40X256 TWRPI socket. SIDE A/SIDE B White DOTS for counting Pins Solder Wire to GND, and to MCU VDD Pin for testing purposes Important Documents TWR-K40X256 User's Manual TWR-K40X256 Schematics External Links TWR-K40X256-KIT Webpage Kinetis Discussion Forum Tower Geeks Community Website Tower Geeks Freescale Cup Group

## Qorivva TRK-MPC5604B Evaluation Board

The TRK-MPC560xB: MPC560xB StarterTRAK (Development Kit) is a Freescale evaluation board powered by the qorivva chip. The Qorivva microcontrollers family is a set of 32 bit Power Architecture chips. Which Chip do you have? The chipset mounted on the boards for the Freescale Cup can vary. Always validate your chipset to know it's full capabilities. MPC560xB Product Information Page Difference Highlights: 5604B = 512MB Code Flash; no DMA 5606B = 1MB Code Flash; Has 16-Channel DMA 5607B = 1.5Mb Code Flash; Has 16-Channel DMA TRK-MPC5604B Hardware Setup There are several main hardware configuration steps. After installing the battery, once the USB cable has been connected between the evaluation board and PC, it may be necessary to update the chip firmware which requires moving a jumper pin on the evaluation board. TRK-MPC5604B Hardware Setup Instructions Lectures: The Freescale Cup – Lecture 5: MPC5607B Overview Overview Slides from lecture Overview Slides from Lecture (PDF) other Lectures from the Freescale Cup Lecture Series Other Qorivva Tutorials: qorivva-blink-led qorivva-drive-dc-motor qorivva-turn-a-servo qorivva-line-scan-camera Board Tips Important Documents TRK-MPC5604B User's Manual TRK-MPC5604BQuick Reference Guide TRK-MPC5604B Schematics Reference manual External Links TRK-MPC5604B Webpage [Qorivva Freescale Hosted Kinetis Discussion Forum] [ ???? Community Website]

## Multi-language-support-enhancements

The pages are being reorganized to better support multiple languages. All pages that were currently in English are being renamed with a prefix "en:" Pages that had prefixes "k40:", "overview", or "qorivva:" will be made into the page name. For example- k40:pagename will be renamed to en:k40-pagename Sorry for any saved bookmark broken links this may cause.

## Discussion of how to setup interrupts on the NVIC. The Flex timer is used as an example

Discussion of how to setup interrupts on the NVIC. The Flex timer is used as an example

## How to use the SysTick peripheral in the Cortex core with interrupts

How to use the SysTick peripheral in the Cortex core with interrupts

## How to setup GPIO on the Kinetis. Includes discussion on enabled clocks to peripherals and setting up the pin control registers

How to setup GPIO on the Kinetis. Includes discussion on enabled clocks to peripherals and setting up the pin control registers.

## Clock setup on the Kwikstik

Clock setup on the Kwikstik

## Part 2 of 2

Kinetis Header Part 2 of 2

## Part 1 of 2

Kinetis Header Part 1 of 2