Development of cargo monitoring system for a rapid response team (disaster aid)

1
Development of cargo monitoring system for
arapid response team (disaster aid)

• Overview of concepts for a real embedded system

2
Disaster Relief Issues

• Disaster likely to be in remote areas
• Roads are blocked, bridges destroyed
  transportation very difficult
• Cargo to be delivered by skid-air drop
• Basically, fly very low over the area, throw out
  a small parachute, cargo-skid is pulled out of
  the aircraft and falls to ground not parachuted
  down
• Mixed cargo
• Perishable goods (food)
• Delicate communication equipment (electronics)
• Need to know if cargo has been abused during
  transportation or delivery

3
Cargo Monitoring System

• During transport
• Quick indication of health of product NOW
• Acceleration in range accuracy of - 1/16 G
• Temperature steady accuracy of - 1 / 32 C
• On delivery
• Display of ranges that cargo has experienced
• Range of temperatures and accelerations
• Other cargo information

4
Overall design
General Purpose Timercontrolling Display
asISR Temperature / Accelerationgraphic
(non-text) displayChanges, actual temperatures
main( )
Play music and monitor light levels might be
nice too
Initialize stuff (C)
Calculate Temperature
Core timerISR clockused forTemperature /
Accelerationdetermination
Store temperature, calculate averages and ranges
Communications with LCDMOSI / MISO format --
ISR Temperature / AccelerationinformationText
format
Calculate Acceleration
Store acceleration, calculate averages and ranges
5
How is the project being split up?

• Devices use pulse-width modulation
• Acceleration Handle through examples in the
  lectures
• Temperature You are handling this in Lab.
  3.This means that all the tests and functions
  developed in the lectures for handling
  acceleration using a pulse-width modulated device
  will need to be modified by you for handling
  temperature
• LCD display SPI interface
• Acceleration Handle through examples in the
  lectures
• Temperature You are handling this in Lab. 4
• This means that all the tests and functions
  developed in the lectures for displaying
  acceleration using am SPI display device will
  need to be modified by you for handling
  temperature

6
Warning

• I plan to do these lectures to document the
  delivery of a design using a test driven
  development approach
• I dont know where the final project (code etc)
  will end up at this moment.
• Design decisions may change as I go along.
• If design decisions change, then I will have to
  change some of my tests and code. HOWEVER, I
  HAVE NO INTENTION OF GOING TO BACK AND MODIFYING
  THE EARLIER LECTURE NOTES. SO KEEP THAT IN MIND
  IF YOU DONT ATTEND ALL THE CLASSES

7
Overall design
General Purpose Timercontrolling Display
asISR Temperature / Accelerationgraphic
(non-text) displayChanges, actual temperatures
main( )
Initialize stuff (C)
Calculate Temperature
Core timerISR clockused forTemperature /
Accelerationdetermination
Store temperature, calculate averages and ranges
Communications with LCDMOSI / MISO format --
ISR Temperature / AccelerationinformationText
format
Calculate Acceleration
Store acceleration, calculate averages and ranges
8
Do the easy part first

• To calculate range
• maxAcc, minAcc, nowAcc need to be determined?
• How to calculate acceleration average?
• Store nowAcc in an array, update the array with
  new values, discard old values?
• Quick indicators needed
• Acceleration stable, increasing, decreasing

Calculate Acceleration
Store acceleration, calculate averages and ranges
9
First problems interpreting requirements

• Quick indicators
• Acceleration stable, increasing, decreasing
• What do these requirements mean?
• Most of the time the cargo will be experienced 1G
  acceleration downwards due to gravity
• Acceleration can occur in 3 dimensions

10
First problems interpreting requirements

• Quick indicators
• Acceleration stable, increasing, decreasing
• What do these requirements mean?
• If we plan to use ADXL213 Dual axis
  accelerometers, then we need 2 ADXL213 Dual axis
  accelerometers
• One doing x and y
• One doing x and z
• Could plan to use the two x-acceleration values
  as cross checks on each other to make sure that
  measuring equipment is working
• How does the accelerometer behave if cargo
  experiences acceleration outside of design limits
  of accelerometer?
• Saturation if bigger acceleration is
  experienced than biggest than can be measured,
  then returns biggest acceleration allowed
• Aliasing wrap-around -- if bigger than biggest
  that can be measured, then looks like smallest
  allowed or perhaps even big in the wrong
  direction like a car odometer (distance) that
  goes to 999999 and then 000000
• Need to find out -- Do some experiments? Manual
  has the information?

11
Design details added
main( )
define ACCELERATION_STEADY 1define
ACCELERATION_DECREASING 2define
ACCELERATION_INCREASING 3 volatile variable
acceleration_changing
Initialize stuff (C)
Calculate Temperature
Communicationbetweenmain( )and ISRmeans
use volatile variables
Store temperature, calculate averages and ranges
General Purpose Timercontrolling Display
asISR Temperature / Accelerationgraphic
(non-text) displayChanges, actual temperatures
Calculate Acceleration
Store acceleration, calculate averages and ranges
12
Develop first test -- Requirements

• variable acceleration_changing is modified in
  main( ) depending on whether current acceleration
  is greater than, equal to, or less than the
  average acceleration
• Display ISR uses this information to modify how
  the LED flash (flicker the lights up
  (acceleration increasing), flicker the lights
  down (acceleration decreasing)), steady lights
  (acceleration reasonably stable within some
  limits), )
• Set_Acceleration_Mode( current_Acc, average_ACC)

13
First Test concept
TEST START acceleration_now
average_acceleration Set_Acceleration_Mode(a
cceleration_now , average_acceleration)
CHECK(acceleration_changing signal shown as
steady) acceleration_now lt
average_acceleration Set_Acceleration_Mode(a
cceleration_now , average_acceleration)
CHECK(acceleration_changing signal shown as
decreasing) acceleration_now gt
average_acceleration Set_Acceleration_Mode(a
cceleration_now , average_acceleration)
CHECK(acceleration_changing signal shown as
increasing) TEST END
14
Three files are going to be needed

• Lab3 directory where product will end up being
  built
• lab3prototypes.h
• define ACCELERATION_STEADY 1
  Lab. 3 TEMPERATURE_STEADYdefine
  ACCELERATION_DECREASING 2 define
  ACCELERATION_INCREASING 3
• void Set_Acceleration_Mode(long int
  current_Acc, long int average_ACC)
• CodeAcceleration.cpp
• Set_Acceleration_Mode( current_Acc,
  average_ACC) All necessary code to
  make function work
• Lab3 tests directory where all tests will be
  built
• TestsAcceleration.cpp
• TEST(Set_Acceleration_Mode, DEVELOPER_TEST)
• All necessary code to test that
  function works

15
Write the test code using E-TDD syntax
include ../Lab3/lab3prototypes.h TEST(Set_Accel
eration_Mode, DEVELOPER_TEST) //
acceleration_now average_acceleration
Set_Acceleration_Mode(6 , 6)
CHECK(acceleration_changing ACCELERATION_STEADY
) // acceleration_now lt
average_acceleration Set_Acceleration_Mode(0
, 6) CHECK(acceleration_changing
ACCELERATION_DECREASING) //
acceleration_now gt average_acceleration
Set_Acceleration_Mode(acceleration_now ,
average_acceleration) CHECK(acceleration_ch
anging ACCELERATION_INCREASING) Now write
the code that satisfies the test
16
Design details added
define ACCELERATION_STEADY 1define
ACCELERATION_DECREASING 2define
ACCELERATION_INCREASING 3 variable
acceleration_changing

• Where is best to place thisvariable
• On the stack?
• As an extern?
• In .section L1_data?

Communicationbetweenmain( )and ISR
General Purpose Timercontrolling Display
asISR Temperature / Accelerationgraphic
(non-text) displayChanges, actual temperatures
Calculate Acceleration
Store acceleration, calculate averages and ranges
17
Where to place variable acceleration_changing?
CHOICE 1 on the stack inside the test
method TEST(Set_Acceleration_Mode,
DEVELOPER_TEST) int acceleration_changing
0 Set_Acceleration_Mode(6 , 6)
CHECK(acceleration_changing ACCELERATION_STEADY
)
CHOICE 2 as an external global variable, with
the variable declared in another file extern int
acceleration_changing TEST(Set_Acceleration_Mode,
DEVELOPER_TEST) Set_Acceleration_Mode(6 ,
6) CHECK(acceleration_changing
ACCELERATION_STEADY)
CHOICE 3 as a global variable, declared in this
file but used by functions in other files int
acceleration_changing 0 TEST(Set_Acceleration_M
ode, DEVELOPER_TEST) Set_Acceleration_Mode(6
, 6) CHECK(acceleration_changing
ACCELERATION_STEADY)
18
What is the correct design decision?Why is that
the correct decision?

• Decision
• Now write the code that satisfies the test

19
Next test Ability to calculate Average

• Ability to calculate an average acceleration
  based on an array of previous acceleration values
• bool CalculateAverage(int previous, int num, int
  average_value)
• previous is the array of previous values
• num is the number of elements in the array
• average_value is the average acceleration
  calculated
• Returns true if the average value can be
  calculated

20
Design details added
Array information is not needed in any global
sense THEREFORE PLACE THE ARRAYON THE STACK
(local variable)

• Where is best to place thearrays used in
  averagingprevious accelerationmeasurements?
• On the stack?
• As an extern?
• In .section L1_data?

General Purpose Timercontrolling Display
asISR Temperature / Accelerationgraphic
(non-text) displayChanges, actual temperatures
Calculate Acceleration
Store acceleration, calculate averages and ranges
21
Write the test code using E-TDD syntax
include ../Lab3/lab3prototypes.h TEST(AverageCa
lculation, DEVELOPER_TEST)
LAB3 Equivalent with Temperature int
previous_values10 0, 0, 2, 2, 1, 1, 10, 10,
10, 10 int average_value 0
bool result true // Empty array --
invalid number of points as array length
result CalculateAverage(previous_values, 0,
average_value) CHECK(result false)
// Average first two values average_value
6 result CalculateAverage(previous_valu
es, 2, average_value) CHECK(result
true) CHECK(average_value 0) //
Average first four values result
CalculateAverage(previous_values, 4,
average_value) CHECK(result true)
CHECK(average_value 1) etc. Now write
the code that satisfies the test
22
Next test Ability to store previous
acceleration values in a defined array

• Need to store values into an array
• Problem suppose array is of size 10 how do
  you store the 11th array entry?
• Answer use circular buffers
• GUI note Dont use function (modulus) as this
  involves a division very slow on this
  processor.
• bool AddToArray(int previous, int num, int
  new_acceleration_value)
• Returns true if the AddToArray( ) operation can
  be performed

23
ReminderHow is the project being split up?

• Devices use pulse-width modulation
• Acceleration Handle through examples in the
  lectures
• Temperature You are handling this in Lab.
  3.This means that all the tests and functions
  developed in the lectures for handling
  acceleration using a pulse-width modulated device
  will need to be modified by you for handling
  temperature
• LCD display SPI interface
• Acceleration Handle through examples in the
  lectures
• Temperature You are handling this in Lab. 4
• This means that all the tests and functions
  developed in the lectures for displaying
  acceleration using am SPI display device will
  need to be modified by you for handling
  temperature

24
Write the test code using E-TDD syntax (1)
include ../Lab3/lab3prototypes.h TEST(AddToArra
y, DEVELOPER_TEST)
LAB3 Equivalent with Temperature define
MAX_ARRAY_SIZE 8 // WOULD THIS BE BETTER
DEFINED INSIDE ../Lab3/lab3prototypes.h?
int previous_valuesMAX_ARRAY_SIZE 0, 0, 0,
0, 0, 0, 0, 0 bool result

// Have a new
acceleration value of 1 add to the array
int expected MAX_ARRAY_SIZE 1, 0, 0, 0, 0,
0, 0, 0 result AddToArray(previous_valu
es, MAX_ARRAY_SIZE, 1) CHECK(result
true) ARRAYS_EQUAL(expected1,
previous_values, MAX_ARRAY_SIZE) // Have
new acceleration values of 2 and then 3 add
those to the array int expected2MAX_ARRAY_S
IZE 1, 2, 3, 0, 0, 0, 0, 0 result
AddToArray(previous_values, MAX_ARRAY_SIZE, 2)
CHECK(result true) result
AddToArray(previous_values, MAX_ARRAY_SIZE, 3)
CHECK(result true)
ARRAYS_EQUAL(expected2, previous_values,
MAX_ARRAY_SIZE) MORE TEST CODE
TO COME .
25
Write the test code using E-TDD syntax (2)
TEST(AddToArray, DEVELOPER_TEST)
LAB3 Equivalent with Temperature Array
TEST CODE CONTINUED // Have new
acceleration values of 2 and then 3 add those
to the array int expected2MAX_ARRAY_SIZE
1, 2, 3, 0, 0, 0, 0, 0 result
AddToArray(previous_values, MAX_ARRAY_SIZE, 2)
result AddToArray(previous_values,
MAX_ARRAY_SIZE, 3) ARRAYS_EQUAL(expected2,
previous_values, MAX_ARRAY_SIZE) // Now add
eight new values to the array that will force a
wrap-around of the array value// Now the three
oldest values have been overwritten // int
expected2MAX_ARRAY_SIZE 1, 2, 3, 0, 0, 0, 0,
0 int expected3MAX_ARRAY_SIZE 9, 10,
11, 4, 5, 6, 7, 8 for (int count
4 count lt 4 MAX_ARRAY_SIZE count)
result AddToArray(previous_values,
MAX_ARRAY_SIZE, count) CHECK(result
true) ARRAYS_EQUAL(expected3,
previous_values, MAX_ARRAY_SIZE) NOW WRITE
THE CODE THAT SATISFIES THE TEST
26
ADXL213 Dual Axis Accelerometer
PF9 PF8
27
Calculation the acceleration using information
from the hardware

• LAB3 Equivalent with Temperature Sensor
• Let us assume that we have measured the time (in
  clock pulses) for T1 (T1_high) and T2 (T2_period)
• Need to develop the tests to check that correctly
  calculate the acceleration when the acceleration
  is in the range 1.7G to -1.7G
• bool CalculateAcceleration(int T1_high, int
  T2_period, int new_acceleration_value)

28
Before tomorrows class

• Write the tests needed to show that
• bool CalculateAcceleration(int, int, int )
• correctly calculates the acceleration when the
  acceleration is in the range 1.7G to -1.7G
• Through this test design identify the design
  defect in the current project design concept for
  the transportation monitoring device

29
Disaster Relief Issues

• Disaster likely to be in remote areas
• Roads are blocked, bridges destroyed
  transportation very difficult
• Cargo to be delivered by skid-air drop
• Basically, fly very low over the area, throw out
  a small parachute, cargo-skid is pulled out and
  falls to ground not parachuted down
• Mixed cargo
• Perishable goods (food), delicate communication
  equipment (electronics)
• Need to know if cargo has been abused during
  transportation or delivery!!!!!!