1. Microcontrollers, Basics Fundamentals of Digital Debugging
19 January 2012
Jonathan A. Titus

2. Digital Debugging
Any discussion of debugging invariable mixes hardware and software.
But do not let debug sessions degenerate into battles between hardware and software people.

3. Digital Debugging Prevent defects from the beginning
Create a best-practices document and programming style
Use Deming’s error-prevention steps
Develop tests and perform unit tests as you go
Write code that tests for limits and errors

4. Digital Debugging Use W Edwards Deming’s error-prevention “loop”
Identify a defect
Find the defect’s root cause
Locate where the defect occurred
Implement preventive practices
Monitor the process to verify effectiveness

5. Digital Debugging
Use a Pareto chart to classify and identify defects:

6. Digital Debugging References
1. "Automated Defect Prevention:Best Practices in Software Management," by Dorota Huizinga and Adam Kolawa, Wiley Interscience, ISBN:

7. Digital Debugging References
2. "Test-Driven Development for Embedded C," James W. Grenning, The Pragmatic Programmers, ISBN:

8. Digital Debugging
Write code that tests for limits and errors...

9. Digital Debugging
Avoid problems: Carefully define specifications for a project:
What happens when someone types an incorrect value, say, $000 at an ATM machine?
What happens when someone continues to key-in incorrect PINs?
Can you handle a printer-out-of-paper condition?
What happens when a communication comes through with an incorrect CRC value?
How do you handle a divide-by-zero error?

10. Simple Hardware Debug Tools
An LED and a pushbutton: simple debug friends:
Basic on-off test or debug indicator
Flash patterns
Start-stop code
Not a recommended debugging technique!
Pushbutton connected to pin for P1.3.

11. Debugger or Emulator? Debug/programming pods:
Direct connection with programming tools
Program MCU flash memory
Debugging capabilities (vary by MCU)
Require 3 to 5 signals
Provide a USB or serial connection to host PC
JTAG signals, but not IEEE-1149 compliant
Often built into dev-kit boards (USB)

12. Debug & Programming Pods

13. Debugging “Messages” Helpful to see your own debug information
Avoid C printf statements -- high code price
Microchip PICKits can operate as a UART
IAR Embedded Workbench has text window
Some dev-kit boards have virtual serial port for simple text communications with host PC.
Jon’s debug “secret weapon”

14. A Debug Secret Weapon...
An inexpensive receipt printer for <$100

15. A Debug Secret Weapon...
Standard logic levels for serial input to printer
Only one pin needed (plus ground)
No drivers or debug module needed
Small amount of code needed for UART
Use bit bashing instead of UART, if necessary
Immediate record of debug messages and data
Good for field testing
Inexpensive--many on ebay (serial, NOT USB!)
Jon’s: Ithaca Series 80PLUS

16. What do Good Debug Tools Do?
Trace execution of code
Watch variables and registers
Set breakpoints
Step through and over code
Quickly make changes to code via IDE and test again
They have limits in real-time situations

17. Presentation of Debug Information

18. ARM Debugging... Wow!

19. ARM Reference
"The Definitive Guide to the ARM Cortex-M3," by Joseph Yiu, Newnes, ISBN:

20. Debugging Hardware Logic Analyzer Oscilloscope Protocol Analyzer
Power-Analysis Hardware and Software

21. Logic Analyzers I

22. Logic Analyzers II

23. Logic Analyzers III

24. Logic Analyzers IV

25. Oscilloscopes I

26. Oscilloscopes II

27. Protocol Analyzers

28. Power Analysis I

29. Power Analysis II

30. Debug Challenges I
Interrupts
Direct-Memory Access

31. Debug Challenges II It’s not always YOUR fault!
Check for revised docs, errata sheets, forum comments, app notes...
MCU sleep mode did not behave as expected.
PWM output did not behave as expected.
Shared USB and serial pins! Not documented.

32. Hed
Text
Bullets If
Needed

33. Hed
Text
Bullets If
Needed