Homework 3: Mbed Setup

ECE 2035 Homework 3: Mbed Setup
The goal of this exercise is to prepare the infrastructure necessary to build an embedded system
using the mbed LPC1768 development board ( http://developer.mbe d.org/). This will be used in
a project that involves interfacing to the mbed, programming, testing and deploying it in an
embedded application.
The mbed is an ARM-based microcontroller manufactured by NXP Semiconductors. ARM is a
RISC instruction set architecture originally developed by Acorn Computers in the early 1980s. It
has become the most widely used 32-bit architecture in terms of number manufactured. There is
at least one ARM processor in 99% of all smartphones and tablets and, as of 2013, over 50
billion products containing an ARM chip have been shipped (Vance 2014). The mbed's ARM
Cortex-M3 core runs at 96MHz with 512KB flash memory and 64KB RAM, and several
communication interfaces, including Ethernet, USB Device, CAN, SPI, I2C, and others.
Task 1: Setup: USB connection and Account Activation
Follow the instructions in the Setup Guide found on the sheet included in the mbed box.
Connect your mbed to your laptop/PC via the USB cable. Click the mbed.html link on the flash
drive that appears. Click signup and note the last few digits of the serial number of your board
on the web page (lower right) as you might need it later (e.g., for serial I/O driver installation).
Set up your account, which will allow you to use the cloud compiler to develop, compile, and
download code for the mbed to execute.
Task 2: Learn proper insertion/removal of mbed
The mbed microcontroller is fragile and inserting it into a breadboard will require some force.
Ensure you line up the holes, then press evenly until it goes into the board fully. If you are not
careful, the pins will break.
Never try to remove the mbed by pulling on the USB lead or USB connector. Do not push down
on the USB connector when pulling out the USB cable. These actions may pull off the USB
connector itself.
It is best to leave the mbed microcontroller in the board whenever possible. If you do need to
remove it, patiently and carefully use a small jewelers screwdriver or similar, and lever it a bit at
a time evenly from each of the four corners in turn, ensuring you pull up with the screwdriver so
you are pressing against the breadboard with the tip and the edge of the microcontroller with the
shaft, rather than the tip touching the bottom of the mbed (which might damage the components
on the underside).
The mbed box contains a small plastic card that shows the pinout diagram for the mbed (also
shown below). This gives pin names that you will use to read or send data values to the pins.
Note that power (3.3V and 5V up to 460MA) is available for the breadboard from the upper pins.
On-chip power circuits produce this voltage using power from the USB cable (500MA max).
Vin is for an external power source like a battery – don't connect anything to it while using the
USB cable. There are four blue user LEDs at the bottom of the board (LED1-- LED4). They are
useful for providing status information. The LEDs will flash if you ever have a run-time error.
Turning power off: Pushing the button on the mbed causes it to reboot, but to turn power off on
the mbed, disconnect the USB cable. The small USB connector on the mbed module is fragile,
ECE 2035 Homework 3: Mbed Setup
so disconnect the larger USB connector that plugs into the PC. If the blue LED is on, you have
power to the mbed. Always turn off power when changing wiring on the breadboard!
If you have never used a breadboard before or if you need to review its underlying connection
patterns, please go to https://mbed.org/handbook/Breadboard for a summary.
LPC1768 Pinout Diagram
Task 3: Download and run a program
After you activate your account, go to the quick start guide for the Arm Mbed OS
https://os.mbed.com/docs/mbed-os/v5.11/quick-start/index.html (choose the online compiler
option) and step through the tasks: run the example on the mbed board by saving the program to
the mbed flash drive and pushing the blue button on the mbed board to reset. The mbed will
always start running the most recently downloaded program. To go directly to the compiler from
the http://developer.mbed.org/ website, select Compiler in the upper right.
Note that the libraries we use to interface the MBED with peripherals are written in C++, but for
the purpose of this class, the game engine and related code are implemented strictly in C.
Task 4: Build the circuit and run test programs
In this task, you will create an embedded system in which the mbed microcontroller interfaces
with a color micro-LCD display, an accelerometer, a microSD card reader, push-buttons and a
small audio speaker. Then, you will download a few test programs to ensure that your system is
wired correctly.
ECE 2035 Homework 3: Mbed Setup
Figure 1: Wiring Diagram
Note the difference between VO and VU. Also be careful to properly orient the BJT transistor (see Fig. 3).
Please note the proper
orientation of the BJT transistor.
Figure 2: Completed Circuit Figure 3: BJT Transistor
Task 4A: The first step is to wire up the components that are provided with the mbed. Follow
the diagram in Figure 1 to wire the mbed microcontroller to each of the components that we will
be using in this project. Note: The speaker is connected to pin 18 in the schematic (via a BJT).
Change the wire connect to pin 18 to pin 26 to use PWM audio in the audio test below in Task
4B. We have let the SD Card in the circuit schmatic in case you wish to use it to store sound
files, but you do not need to wire it in or test it unless you actually use it in P2-2. In that case,
you would need to use pin 18 for audio.
An example of the completed circuit is shown in Figure 2.
ECE 2035 Homework 3: Mbed Setup
mbed to uLCD connection
Also, note that the transmit (TX) pin of the mbed (pin 9) connects to the receive (RX) pin of the
uLCD and the RX pin of the mbed (pin 10) connects to the TX pin of the uLCD. The ribbon
cable that is used to connect the mbed to the uLCD has labels (RX and TX) that refer to the
mbed's RX and TX pins, not the uLCD's pins. The ribbon cable is plugged into the bottom row
of pins on the uLCD (the row closest to the edge).
Please see http://developer.mbed.org/users/4180_1/notebook/ulcd-144-g2-128-by-128-color-lcd/
for close up views of the uLCD pins and the uLCD ribbon cable with details of the proper
wiring.
Task 4B. Run the following test programs:
1. 2035_P2_PB_LED: This test program uses the existing 4 LED lights on mbed, and 3
pushbuttons to create runway light effects.
Pushbuttons
Behavior
p23: increase the frequency of lights
p22: pause the runway lights
p21: decrease the frequency of lights
Reference: https://os.mbed.com/users/4180_1/notebook/led-lighting-effects-for-modelers/
2. 2035_P2_LCD: This test program displays a bouncing red ball through uLCD display.
Reference: https://os.mbed.com/users/4180_1/notebook/ulcd-144-g2-128-by-128-color-lcd/
3. 2035_P2_Accelerometer_LCD: The test program displays a red ball on the uLCD screen.
Different from 2035_P2_LCD demo, the red ball moves on uLCD screen based on accelerometer
readings. LCD and accelerometer connections should be the same as illustrated in the reference.
ECE 2035 Homework 3: Mbed Setup
Accelerometer
References: https://os.mbed.com/components/MMA8452Q-Triple-Axis-Accelerometer/
https://learn.sparkfun.com/tutorials/mbed-starter-kit-experiment-guide/experiment-4-
accelerometer
4. 2035_P2_Speaker_PWM:
The test program uses mbed’s PWM hardware output to play 3 different tones triggered by
pushbuttons. The speaker should be set up according to the reference.
Behavior
p21: 100Hz tone
p22: 300Hz tone
p23: 500Hz tone
Reference: https://os.mbed.com/users/4180_1/notebook/using-a-speaker-for-audio-output/
Task 4C. Download P2-baseline.bin and play with the baseline version of P2.
This game is a simplified version of the Gameboy Advance versions of Fire Emblem. It is a two
player turn based strategy game set in a 2D grid world with a top down view.
In this baseline implementation, there are two players that each control three characters, denoted
with red and green squares, respectively.
You start out in free roam mode, in which you can freely navigate the world by tilting the mbed
(making use of the accelerometer) to move your gray cursor. You can either use the action button
on a character that you control to select them, or use the back button to end your turn.
Once a character has been selected, you can move them up to a certain distance away
(configurable for each character). If the character has been moved next to an enemy character,
they fight and deal damage to each other according to their stats (each character has an attack,
defense, and hit points).
Once a character’s hit points (HP) reaches zero, they die and are removed from the map.
The objective of the game is to kill all of your opponent's characters.
ECE 2035 Homework 3: Mbed Setup
The red characters (controlled by player one) are viewable at the start of the game. The green
characters, controlled by player two, can be found to the southeast.
Homework 3 Check-off
Once you have successfully created the circuit in Figure 1, and can successfully run the test
programs, demo your working system to a teaching assistant by the deadline to get
Homework 3 checked off for a grade.
References
1. A. Vance, “ARM Designs One of the World's Most-Used Products. So Where's the
Money?” Bloomberg Businessweek, 4 February 2014, available online at:
http://www.bloomberg.com/bw/articles/2014-02-04/arm-chips-are-the-most-usedconsumer-product-dot-where-s-the-money
2. Mbed Pinout:
http://developer.mbed.org/handbook/mbed-NXP-LPC2368
3. Mbed-NXP Pinout:
http://developer.mbed.org/users/synvox/notebook/lpc1768-pinout-with-labelled-mbed-pins/
4. NXP-LPC1768 User’s Manual:
http://www.nxp.com/documents/user_manual/UM10360.pdf