ECE 300 Embedded Microcontroller Project

1
ECE 300Embedded Microcontroller Project

• Group 4
• Bryan Bollinger
• Molly Kryder
• David Windsor
• Brian Washington

2
Things to pick up along the way

• To learn about embedded systems
• To gain basic knowledge and working experience
  with soldering on a small scale
• To learn to apply basic troubleshooting knowledge
  of circuits
• To become more familiar with the design process
  and working in a group environment

3
Goals What exactly needs to be accomplished?

• Construct a functioning board
• Power the microcontroller
• Successfully Flash the microcontroller
• Power and drive the LCD
• Interface the board with a sensor
• Choose an appropriate device
• Connect the sensor to the microcontroller
• Scale and display the output

4
MSP430The microcontroller in question

• Low Supply-Voltage Range, 1.8 V to 3.6 V
• Lithium and Alkaline voltage range, easy to
  produce
• 12-Bit A/D Converter With Internal Reference,
  Sample-and-Hold and Autoscan Feature
• No need for us to convert analog to digital
• Integrated LCD Driver for Up to 160 Segments
• No need to write a new interface to drive the LCD
• MSP430F449       60KB256B Flash Memory, 2KB
  RAM
• Flexibility for coding

5
Board Construction

• Team Meeting to practice soldering with the
  surface mount components and the chip
• Resistors
• Capacitors
• Processor
• Final Board Construction
• A unified soldering method should be decided upon
  to complete the board, in order to minimize
  possible soldering error and repair time

6
Problems

• Missing Kit Components
• -no polarized capacitors, only one MSP430, no
  voltage converter
• Soldering Problems
• -melted a part of the LCD cover, fused the
  oscillator crystal leads, first chip soldered
  incorrectly
• Mostly minor problems, but the frequency of the
  problems and the time necessary to retool between
  them
• (i.e. time required to obtain replacements
  etc.)
• caused initial construction to take much longer
  than expected

7
Testing and Troubleshooting

• Initial Flashes were not successful
• Learned it was an operator error as the Flash
  Emulation Tool was upside down, another delay
• Subsequent Flashes
• Reported success but the LCD showed incoherent
  digits
• Shortly thereafter, the LCD showed nothing at all

8
Testing and Troubleshooting

• Possible Causes of Error
• Heat Damaged Chip
• Mismanufactured Chip
• Damaged LCD
• Bad Solder Joints
• Further study of the board with a voltmeter
  revealed some bad solder joints which were then
  repaired
• LCD still showed garbage, but at least it showed
  something

9
Testing and Troubleshooting

• All points on the LCD had continuity to their
  respective pin on the microprocessor, but still
  something was not functioning properly
• Starting a new board recommended
• About this time, another group member began their
  own board, just in case the current board could
  not be repaired
• The board warranted further testing, so more time
  was committed to experimentation
• An exact-o-knife was used to check the solder
  joints and traces from the microprocessor to the
  board
• During this process, the LCD managed to show a
  broken HELLO

10
Testing and Troubleshooting

• Adding tiny amounts of solder to each of the pins
  of the chip resulted in a fully functional board
• Another meet to show the board to the team, the
  LCD would fade in and out, apparently a capacitor
  problem
• Board Finally Successfully Displays Hello 888
  message consistently

11
Sensor Selection

• Several Types of Analog Sensors Group Members
  Considered
• Temperature Analog Devices 22100, 22103
• Magnetic Field Sentron CSA1V, AD 22151G
• Infrared - Sharp GP2D12
• Ultrasonic Transducer - USONICPNPA
• RPM Sensor

12
Quick Sensor Reference
Temperature Magnetic Field Infrared Ultrasonic
Cost FREE FREE 10 60
Expected Ease of Interface Easy Midrange Midrange Difficult
Expected Ease to Test Easy Difficult Easy Easy
13
More Sensor Selection

• Ease of use of the temperature sensor made it
  very appealing, but there were several models to
  choose from
• The Analog Devices AD22103 is an analog, low
  power, 3.3V device with a temperature range from
  0 to 100 Celsius and it was available in a 3 pin
  TO-92 Package as opposed to the way many of its
  cousins and competitors were, an 8 pin package

14
Interfacing the Sensor and Board

• Sensor needed
• Power
• which was drawn from a spot on the board labeled
  Vcc which provided 2.85 V
• Common ground of the board
• a spot for a banana plug lead was drilled and
  connected to one of the boards several common
  grounds
• Voltage out to go to the A/D of the MSP430
• again a spot for a banana plug lead was drilled
  and a wire was run to this location

15
Analyzing the Code

• The code provided took the input from the A/D and
  converted it to a voltage 100 and stored it in
  a floating variable called sample. The times 100
  comes into play later when displaying results to
  the LCD
• The AD22103 Datasheet provided a Transfer
  Function to convert this voltage into a
  temperature in degrees Celsius

Rearranging the Equation and Solving for TA
gives
16
More Changes

• Celsius is the standard temperature scale, but
  Fahrenheit is easier for most people to relate to
• To convert from C to F, simply use the equation
  below
• (1.8 C) 32
• This was an easy modification to the code

17
A glimpse of the code

• sample ADC12MEM6
• sample sample A
• B (3.3 / 2.85) / .028
• sample sample B
• sample sample - (.25 / .028)100
• sample (sample 1.8) 3200
• lcd_word(sample,2)
• Its time to recall the fact that the board is
  storing and sampling the voltage times 100.
  Because of this, all constants need to be
  multiplied by 100. The reason for this is pretty
  obvious if you look the way in which the LCD
  driver functions operate. They take the number
  and perform modulus division on the sample to
  find out the value of the thousands place, the
  hundreds place, the tens place, and the ones
  place and it sends it to the 3rd segment, 2nd
  segment, 1st segment, and 0th segment
  respectively.

18
An Example

• What if it were 72.35 degrees in this room?
• Then the value of sample after the conversions
  would be 7,235 so the processor would try to
  figure out what to send each segment one at a
  time

Segment 3 7,235 / 1000 7.235 10 7.235
0 7 Segment 2 7,235 / 100 72.35 10
2.35 0 2 Segment 1 7,235 / 10
723.5 10 3.5 0 3 Segment 0 7,235
/ 1 7,235 10 5 0 5
19
Future Changes

• Make the board perform an action when a condition
  is met
• Turn on an LED
• Make a noise with a small buzzer
• Such tasks would require only a small amount of
  additional knowledge of the chip and its
  interrupt system

20
Some pictures
Back of the board
Front of the Board
AD22103 Temp Sensor