Embo++2022 Unembedding Embedded Systems with TDD Benefits of going beyond the Make-It-Work phase.pdf

'Unembedding' embedded systems
with TDD
Benefits of going beyond the
Make It Work phase

About Me & Talk Objectives
• Telecommunication Engineer, majoring in electronics.
• 16 years surviving from the trenches:
• Hardware (trying to domain the ‘Black magic’).
• Firmware & Software.
• DevOps & Agile Coach.
• Helping organizations to improve their development processes
• ...
• Sectors: automotive, microelectronics, defense, railway, renewable energies, fishery…
@fraclipe
@FranciscoClimentPerez
www.francliment.com
.francliment.com

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Peripheral
MCUx
IC1
IC2
Peripheral
Embedded System: Hardware, Firmware and … Software?

HARDWARE
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Peripheral
MCUx
IC1
IC2
Peripheral

HARDWARE
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Peripheral
MCUx
IC1
IC2
Peripheral
?

HARDWARE
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Peripheral
IC1
IC2
Peripheral
MCUx
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs

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Special Function Registers (SFRs): The Hardware interface

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Nothing happens ‘outside’
if it doesn’t change an SFR bit

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Peripheral
IC1
IC2
Peripheral
MCUx
Embedded
CODE
(SW // FW)
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs

“Software is this thing that can have a long
useful life, but firmware will become
obsolete as hardware evolves”
Updated definition:
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(Re)Definition of Firmware
Software engineer and author. Co-author of the Agile
Manifesto. Author of ‘Test Driven Development for
Embedded C’.
― James W. Greening, Clean Architecture
[Robert C. Martin]

Updated definition:
.francliment.com
Embedded C’.
“Firmware is firmware because of what it
depends on and how hard is to change
those dependencies”.
[Robert C. Martin]

Updated definition:
.francliment.com
Embedded C’.
[Robert C. Martin]
“Firmware is firmware because of what it
depends on and how hard is to change
those dependencies”.
“… Non-embedded developers also write
firmware whenever they bury SQL in their code
or when they spread platform dependencies
throughout their code and business logic …”

1. Make It Work
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Development as 3 strategic steps
3. Make It Fast
2. Make It Right
https://www.eetindia.co.in/engineers-in-the-covid-19-era/
https://www.ee,tindia.co.in/engineers-in-the-covid-19-era/
― Kent Beck, Test-Driven Development By Example, 2003
― Butler W. Lampson, ’Hints for Computer System Design’, 1983
― Stephen C. Johnson & Brian W. Kernighan, ’The C Language and Models for Systems Programming’, 1983

1. Make It Work
.francliment.com
3. Make It Fast
2. Make It Right
Focused in understanding how to solve the problem, not about
engineering the code right

1. Make It Work
.francliment.com
3. Make It Fast
2. Make It Right
Engineer and craft the code right to make it easy to
understand, maintain and evolve

1. Make It Work
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3. Make It Fast
2. Make It Right
Fulfill system timing requirements (if any)

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Fallacies & Mantras

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“Right solution at first iteration”
THE BIGGEST LIE EVER

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Making It Work: Embedded is harder
Orders of magnitude harder in
embedded.
1. Make It Work

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Peripheral
MCUx
IC1
Application
(Main God)
HW
IC2
Peripheral
Making It Work: Main God
<use>
<use>
<use>
<use>
<use>
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs

.francliment.com
Peripheral
MCUx
IC1
Application
(Main God)
HW
IC2
Peripheral
<use>
<use>
<use>
<use>
<use>
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs

.francliment.com
Peripheral
MCUx
IC1
Application
(Main God)
HW
IC2
Peripheral
<use>
<use>
<use>
<use>
<use>
MCUx
Family
Cross-
Compiler
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs

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Making It Work: Cross-Compiler ‘aids’

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Peripheral
MCUx
IC1
Application
(Main God)
HW
IC2
Peripheral
<use>
<use>
<use>
<use>
<use>
MCUx
Family
Cross-
Compiler
Hardware
Components
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs

.francliment.com
Peripheral
MCUx
IC1
Application
(Main God)
HW
IC2
Peripheral
<use>
<use>
<use>
<use>
<use>
MCUx
Family
Cross-
Compiler
Hardware
Components
Hardware
Layout
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs

.francliment.com
Peripheral
MCUx
IC1
Application
(Main God)
IC2
Peripheral
<use>
<use>
<use>
<use>
<use>
MCUx
Family
Cross-
Compiler
Hardware
Components
HW
MCU & HW PLATFORM
FIRMWARE
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
Hardware
Layout

.francliment.com
Peripheral
MCUx
IC1
Application
(Main God)
IC2
Peripheral
<use>
<use>
<use>
<use>
<use>
MCUx
Family
Cross-
Compiler
Hardware
Components
HW
MCU & HW PLATFORM
FIRMWARE
D
S
O
I
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
Hardware
Layout

Layers
LAYERS
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Peripheral
MCUx
IC1
IC
DRIVERS
App
IC
DRIVERS
IC2
Peripheral
Evolution: The Drivers Layer
BUSSINESS
LOGIC
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
HW

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Peripheral
MCUx
IC1
App
IC
DRIVERS
IC2
Peripheral
BUSSINESS
LOGIC
IC1
Driver
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
HW
IC
DRIVERS

.francliment.com
Peripheral
MCUx
IC1
App
IC
DRIVERS
IC2
Peripheral
BUSSINESS
LOGIC
IC1
Driver
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
<use>
HW
IC
DRIVERS

.francliment.com
Peripheral
MCUx
IC1
App
IC
DRIVERS
IC2
Peripheral
BUSSINESS
LOGIC
IC1
Driver
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
<use>
HW
MCUx
Family
Cross-
Compiler
IC
DRIVERS

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Peripheral
MCUx
IC1
App
IC
DRIVERS
IC2
Peripheral
BUSSINESS
LOGIC
IC1
Driver
D
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
<use>
HW
MCUx
Family
Cross-
Compiler
IC
DRIVERS

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Peripheral
MCUx
IC1
App
IC
DRIVERS
IC2
Peripheral
BUSSINESS
LOGIC
<use>
IC1
Driver
D
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
<use>
HW
MCUx
Family
Cross-
Compiler
IC
DRIVERS

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Peripheral
MCUx
IC1
App
IC
DRIVERS
IC2
Peripheral
BUSSINESS
LOGIC
Hardware
Components
<use>
IC1
Driver
D
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
<use>
HW
MCUx
Family
Cross-
Compiler
IC
DRIVERS

.francliment.com
Peripheral
MCUx
IC1
App
IC
DRIVERS
IC2
Peripheral
BUSSINESS
LOGIC
D
Hardware
Components
<use>
IC1
Driver
D
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
<use>
HW
MCUx
Family
Cross-
Compiler
IC
DRIVERS

.francliment.com
Peripheral
MCUx
IC1
App
IC
DRIVERS
IC2
Peripheral
BUSSINESS
LOGIC
D
O
Hardware
Components
<use>
IC1
Driver
D
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
<use>
HW
MCUx
Family
Cross-
Compiler
IC
DRIVERS

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Peripheral
MCUx
IC1
App
IC
DRIVERS
IC2
Peripheral
BUSSINESS
LOGIC
D
O
Hardware
Components
‘Components’
Firmware
MCU
Firmware
<use>
IC1
Driver
D
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
<use>
HW
Evolution: The Drivers (Illusion) Layer
MCUx
Family
Cross-
Compiler
IC
DRIVERS

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• No long life SW (Domain, Application or Business Entities?)
• Nothing is modular or reusable
• Impossible to test any part in isolation
• Manual testing/debugging.
• Expensive and hardly repeatable ‘process’
Making It Work: MCU & HW PLATFORM FIRMWARE
PROBLEMS (common):
ALL EVIL SEEDS:
• Fragile
• Immobile
• Needless complexity
• Needless repetition
• Opaque
• Rigid

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PROBLEMS (Ditto due to being embedded):
• Expensive & scarce powering, input generation and output measurement
equipment is needed
Source: https://www.appliedinnovationalliance.com/wp-content/uploads/2017/12/Bottleneck-1.png
• Compiles only with the selected cross-compiler
• Executes only under an specific MCU family (MCUx)
• Runs only under an specific hardware platform (PCB assembly)
Making It Work: MCU & HW PLATFORM FIRMWARE

Hardware
Bottleneck
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Source: https://www.eetindia.co.in/engineers-in-the-covid-19-era/
Embedded Stockholm Syndrome

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Peripheral
IC1
IC2
Peripheral
MCUx
Embedded
CODE
(SW // FW)
Hardware Bottleneck problems: Defect localization
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs

HW
GROUP
FW
GROUP
When new code is tested directly on Hardware (Debug on Hardware) and it does not
work as expected…
Where is the problem located?,
Is it HW?, is it FW?, both?
FW ERROR HW ERROR
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EMBEDDED TEAM?
Hardware Bottleneck problems: Defect localization

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Example: Microelectronics M28W160ECT (16MB flash) Driver
Hardware Bottleneck problems: Untested behaviors

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HAPPY PATH

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HAPPY PATH
SAD PATH

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HAPPY PATH
SAD PATH
How do we test these
situations on the HW?

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About Testing Anti-patterns:
https://marabesi.com/tdd/2021/08/28/tdd-anti-patterns.html

It ‘Works’… finally?
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BRING-UP

“Starting from
nowhere, we have
reached the
highest levels of
misery …”
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WHY?

VENDOR’s
#TRAP
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Embedded Traps: Vendor’s partnership

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Vendor’s IDEs, frameworks, utilities, toolchains,
libraries… MUST BE low level details properly
hidden & decoupled from our application

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The vendor is NOT our partner

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The vendor is NOT our partner
The running processor is a low level DETAIL

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Source: https://www.bangkokpost.com/business/2117491/the-chips-are-down

COMPLIANCE MINDSET
#TRAP
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Embedded Traps: Compliance Mindset

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New features,
Added functionality
Architectural,
Structural features
Defects
Technical Debt
Positive
Value
Negative
Value
Value
Visibility
Invisible Visible
Quality as 4 quadrants

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New features,
Added functionality
Architectural,
Structural features
Defects
Technical Debt
Positive
Value
Negative
Value
Value
Visibility
Invisible Visible
Quality as 4 quadrants
External
Quality

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External Quality: Defects & BIT level sensitivity
Arianne 5: ‘A 40 seconds flight’

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https://hackaday.com/2015/10/26/killed-by-
a-machine-the-therac-25/
Teradyne-25
Therac-25
‘extra-dose’
Source: https://hackaday.com/2015/10/26/killed-
by-a-machine-the-therac-25/

Source: http://www.eetimes.com/document.asp?doc_id=1319903&page_number=1
.francliment.com

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• ISO 26262 for automotive electric/electronic systems.
• EN 50128 for railway applications.
• IEC 62304 for medical devices.
• IEC 62061 for machinery systems.
IEC 61508
Functional safety of electrical/electronic/programmable
electronic safety-related systems
Embedded Traps: Compliance Mindset

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Table B.2 – Dynamic analysis and testing
IEC 61508: Code Coverage

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Mutation Testing Intro
Automated fault injection
technique aimed to find
counterexamples to this
conjecture:
“Our test suite is
comprehensive because
it has 100% code
coverage”

Mutation Testing Example: Uncovered code
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“Code coverage is an useless metric”
Fallacies & Mantras: Code coverage utility

Mutation Testing Example: The whispering mutants
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Mutation Testing Example: The missing cornercase

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Source: https://www.researchgate.net/publication/317160803_An_empirical_study_on_the_application_of_mutation_testing_for_a_safety-critical_industrial_software_system
Compliance Mindset Example (I)

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External quality
Compliance Mindset Example (II): Results

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200 -------- 2
27.158 ---- X X = 271 faults!
External quality
Compliance Mindset Example (II): Results

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“Code coverage is a harmful metric”
Fallacies & Mantras: Code coverage utility

TAKEAWAYS
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Takeaways

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Takeaways: Professional Attitude
Cheating the metrics is a sign
of bigger cultural problems

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Source: http://knowreqts.yolasite.com/resources/2.20%20%20Empirical%20Evaluation.pdf
Compliance Mindset Example (II)

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Takeaways: Better protect yourself
Nobody but the organization itself
is going to take care about its
reputation, development,
aftersales and health costs

DEVIATED FOCUS
#TRAP
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Common Traps: Deviated Focus

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New features,
Added functionality
Architectural,
Structural features
Defects
Technical Debt
Positive
Value
Negative
Value
Visibility
Invisible Visible
External
Quality
External Quality is only an effect …
Value

1. Make It Work
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Red
Green
Refactor

1. Make It Work
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Red
Green
Refactor
Make It Work

1. Make It Work
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Red
Green
Refactor
Make It Work
KISS: Keep It Simple, Stupid
YAGNI: You Aren’t Gonna Need It

1. Make It Work
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Red
Green
Refactor
Make It Work
“All sins are allowed”

Red
Green
Refactor
2. Make It Right
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Make It Work

Red
Green
Refactor
2. Make It Right
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Make It Work
Make It Right
Test code only
DAMP : Descriptive And
Maintainable Procedures
2
KISS : Keep it Simple, Stupid
1
DRY : Don’t Repeat Yourself
1
2
Production code only
1

Red
Green
Refactor
2. Make It Right
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Make It Work
Make It Right
Test code only
2
1
1
2
1
Simple Design,
SOLID,
Design Patterns…

Internal
Quality
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New features,
Added functionality
Architectural,
Structural features
Defects
Technical Debt
Positive
Value
Negative
Value
Visibility
Invisible Visible
External
Quality
Value
Quality comes from inside

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How does Internal Quality looks like?

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X = 271 faults!
External quality

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X = 271 faults!
Internal quality
External quality

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X = 271 faults!
Internal quality
External quality
S

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“We can get the same benefits
following a Test-Later approach”
Fallacies & Mantras: Test-Later vs Test-First

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“We can get the same benefits
following a Test-Later approach”
Test-Later are testing techniques focused on
External Quality only
Fallacies & Mantras: Test-Later vs Test-First

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Takeaways: Quality is not coffe sugar
― Harold F. Dodge
“Inspection does not improve the quality,
nor guarantee quality.
Inspection is too late.
The quality, good or bad, is already in the product”

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What about Agile/Xp in safety-related environments?

3. Make It Fast
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Make It Right
Fulfill timing requirements

GLOBAL PERFORMANCE
PRE-OPTIMIZATION
#TRAP
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Embedded Trap: Nedless performance

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“Even if you know exactly what is going on in your system,
measure performance, don’t speculate.
You will learn something, and 9 times of 10, it won’t
be that you were right!”
― Ron Jeffries, Refactoring: Improving the Design of
Existing Code [Fowler]
Embedded Trap: Nedless performance

3. Make It Fast (enough)
.francliment.com
Make It Work
Make It Right
Fulfill timing requirements (only when & where are really
needed).

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Red
Green
Refactor
Make It Work
Make It Right
needed).
1. Add the timing spec

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Red
Green
Refactor
2. Make It Work
Make It Right
needed).

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Red
Green
Refactor
2. Make It Work
Make It Right
needed).
Test code only
2
1
1
2
1
Simple Design,
SOLID,
Design Patterns…

.francliment.com
Takeaways: Right tunable software
“The secret of fast software is to write tunable
software first and then tune it for
sufficient speed”
― Martin Fowler, Refactoring: Improving the Design of
Existing Code

KNOWLEDGE & SKILLS
#TRAP
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Common Traps: Knowledge & Skills

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Common Traps: Knowledge & Skills
“The competent programmer is fully aware of the limited size of his
own skull. He therefore approaches his task with full humility, and
avoids clever tricks like the plague.”
— Edsger W. Dijkstra

.francliment.com
Source: https://www.eetindia.co.in/engineers-in-the-covid-19-era/
Moving the quality boundary forward
Making It Work,
Survival mode
Making It Right,
Professing engineering

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A new approach …
DevOps
OUTSIDE
Embedded
limits

Embedded TDD: Dual-Target work flow
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HOST DEVELOPMENT ENVIRONMENT
HOST BASED FLOW
Embedded TDD cycle
Source: “Test-Driven Development for Embedded C” book, James Greening

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HOST BASED FLOW
Generate
self-checking
specs
Embedded TDD cycle

Embedded TDD cycle
.francliment.com
HOST BASED FLOW
Generate
self-checking
specs
Fulfill the
specs

.francliment.com
HOST BASED FLOW
Generate
self-checking
specs
Fulfill the
specs
Improve the
solution
Embedded TDD cycle

.francliment.com
HOST BASED FLOW
Generate
self-checking
specs
Review results and metrics
Embedded TDD cycle
Fulfill the
specs
Improve the
solution

.francliment.com
HOST BASED FLOW
Generate
self-checking
specs
Embedded TDD cycle
Cadence: 1 min
Fulfill the
specs
Improve the
solution

Embedded TDD cycle
.francliment.com
HOST BASED FLOW
TARGET BASED FLOW
Generate
self-checking
specs
Fulfill the
specs
Improve the
solution

Embedded TDD cycle
.francliment.com
HOST BASED FLOW
TARGET BASED FLOW
Generate
self-checking
specs
Cross
compile
Fulfill the
specs
Improve the
solution

Embedded TDD cycle
.francliment.com
HOST BASED FLOW
TARGET BASED FLOW
Generate
self-checking
specs
Cross
compile
Eval Hardware
Fulfill the
specs
Improve the
solution

Embedded TDD cycle
.francliment.com
HOST BASED FLOW
TARGET BASED FLOW
Generate
self-checking
specs
Cross
compile
MCU Simulator
Fulfill the
specs
Improve the
solution

Embedded TDD cycle
.francliment.com
HOST BASED FLOW
TARGET BASED FLOW
Generate
self-checking
specs
Cross
compile
MCU Simulator
Cadence: 5 min
Fulfill the
specs
Improve the
solution

.francliment.com
NO FEAR
Dual-Target Embedded TDD: Main Benefits
OUTSIDE
Embedded
limits
• Incrementally developed
• Comprehensively tested at least on two different platforms
• Fast feedback loop: courage to try & learn fast

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NO FEAR
OUTSIDE
Embedded
limits
NO LIMITS
✓ Static analysis, rule checkers …
✓ Dynamic análisis: xUnit, mutation testing
✓ Continuous Integration / Continuous Testing
New tools finally avilable:
Working on
99% code base

HOST
- Static analysis (scan-build, sonarcube, …).
- Dynamic analysis:
- Unit testing (Ceedling + GCC + HOST execution)
- Integration testing (Ceedling + GCC + HOST execution)
- Mutation testing (Ceedling + GCC + Clang-AST)
- Metrics / Trends:
- Code coverage.
- Mutantes coverage
- Cyclomatic complexity
XC
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Dual-Target Continuous Integration / Continuous Testing

TARGET
- Dynamic analysis:
- Unit testing (Ceedling + XC + PIC (mdb) simulator)
- Integration testing (Ceedling + XC + PIC (mdb) simulator)
- Metrics / Trends:
- Target compilation warnings (Ceedling + XC, at project level).
- ROM & RAM used (Ceedling + XC, at project level).
- STACK used (Ceedling + XC, at project level).
XC
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XC
Build result ‘#17- 44-modbus_controller’: UNSTABLE
Artifacts associated to build ‘#17- 44-modbus_controller
Changes associated to the push originating the build
‘#17- 44-modbus_controller
Coverage statistics for build
function is_Synt_lock
@fraclipe
Tests results for build ‘#17- 44-modbus_controller
Warnings detected for build ‘#17- 44-modbus_controller
Warnings’ changes from last build
Identified probles for build
Build Log
XC Warnings
44-modbus_controller #17 - 44-modbus_controller
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Reusable modules
Domain Driven Embedded
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Peripheral
MCUx
IC1
DRIVERS
App
HW
HARDWARE
COMPONENTS
IC2
Peripheral
Making It Right: Towards Reusable Drivers
BUSSINESS
LOGIC
D
O
<use>
IC1
Driver
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs

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Peripheral
MCUx
IC1
DRIVERS
App
P
A
L
IC2
Peripheral
D
O
BUSSINESS
LOGIC
<use>
IC1
Driver
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
HW
Processor Abstraction Layer
HARDWARE
COMPONENTS

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Peripheral
MCUx
IC1
DRIVERS
App
P
A
L
HARDWARE
COMPONENTS
IC2
Peripheral
D
O
BUSSINESS
LOGIC
<use>
IC1
Driver
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
HW
<use>
P
A
L
I
m
p
l
implements

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Peripheral
MCUx
IC1
DRIVERS
App
P
A
L
HARDWARE
COMPONENTS
IC2
Peripheral
D
O
BUSSINESS
LOGIC
<use>
IC1
Driver
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
HW
<use>
P
A
L
I
m
p
l
implements
<use>

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Peripheral
MCUx
IC1
DRIVERS
App
P
A
L
HARDWARE
COMPONENTS
IC2
Peripheral
D
O
BUSSINESS
LOGIC
<use>
IC1
Driver
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
HW
<use>
P
A
L
I
m
p
l
implements
<use>
MCUx
Family

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Peripheral
MCUx
IC1
DRIVERS
App
P
A
L
HARDWARE
COMPONENTS
IC2
Peripheral
D
O
BUSSINESS
LOGIC
<use>
IC1
Driver
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
HW
<use>
P
A
L
I
m
p
l
implements
<use>
Cross-
Compiler
MCUx
Family

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Peripheral
MCUx
IC1
DRIVERS
App
P
A
L
HARDWARE
COMPONENTS
IC2
Peripheral
D
O
BUSSINESS
LOGIC
<use>
IC1
Driver
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
HW
<use>
P
A
L
I
m
p
l
implements
<use>
FW
MCU
Firmware
Cross-
Compiler
MCUx
Family

ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
App
(SW)
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
MCU FW
HARDWARE
COMPONENTS
BUSSINESS
LOGIC
Software
S
Y
S
C
O
M
P
O
N
E
N
T
S
I
M
P
L
Components
Factory
<use>
P
A
L
<use>
<use>
<use>
<use>
<use>
P
A
L
I
M
P
L
M
C
U
x
implements
Test
Doubles
REUSABLE
IC
DRIVERS
ARRANGE/ASSERT
implements
<use>
IC
Drivers
Test
Suite
Making It Right: Reusable Drivers implementation (Dual-Targetted)
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ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
App
(SW)
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
MCU FW
HARDWARE
COMPONENTS
BUSSINESS
LOGIC
Software
S
Y
S
C
O
M
P
O
N
E
N
T
S
I
M
P
L
Components
Factory
<use>
P
A
L
<use>
<use>
<use>
<use>
<use>
P
A
L
I
M
P
L
M
C
U
x
implements
Test
Doubles
ARRANGE/ASSERT
ACT
implements
<use>
IC
Drivers
Test
Suite
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REUSABLE
IC
DRIVERS

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Takeaways: Reusable IC Drivers test suite goals
IC Drivers test suite GOALS
Capture our IC datasheet interpretation, allowing:
▪ Implement the IC Driver accordingly to it without introducing errors
▪ Hardware Bottleneck related uncertainties and delays removal

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TDDing Firmware
Making It Right: MCUx PAL implementation (Target only)

App
(SW)
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
COMPONENTS
IMPLEMENTATION
(HWy)
Components
Factory
<use>
P
A
L
<use>
<use>
<use>
<use>
<use>
PAL
IMPLEMENTATION
(MCUx)
implements implements
PAL ASSERTS
Step Spied
PAL implements
PAL
MCUx
ASSERTS
ARRANGE
ACT
ASSERT
implements
PAL Test
Suite
MCU FW
PAL Spies PAL
MCUx SPIES
implements
ARRANGE
HW
<use>
<read>
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
Step
Spied
MCUx
PAL
<use>
<read>
Making It Right: MCUx PAL implementation (Target only)
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PAL production code example: ADC reading independent of MCU
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Takeaways: MCU PAL test suite goals
MCU PAL test suite GOALS
Capture our MCU datasheet interpretation, allowing:
▪ Implement its PAL accordingly to it without introducing errors.
▪ Use the MCU in our solution.
▪ Hardware Bottleneck related uncertainties and delays removal.

App
(SW)
HW
HARDWARE
COMPONENTS
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
P
A
L
<use>
<use>
<use>
PAL
IMPLEMENTATION
(MCUx)
implements
MCU FW
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
D
O
Making It Right: Towards Embedded Business Software
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App
(SW)
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
P
A
L
<use>
<use>
<use>
PAL
IMPLEMENTATION
(MCUx)
implements
MCU FW
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
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App
(SW)
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
P
A
L
<use>
<use>
<use>
PAL
IMPLEMENTATION
(MCUx)
implements
MCU FW
COMPONENTS
IMPLEMENTATION
(HWy)
implements
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
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App
(SW)
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
P
A
L
<use>
<use>
<use>
PAL
IMPLEMENTATION
(MCUx)
implements
MCU FW
COMPONENTS
IMPLEMENTATION
(HWy)
implements
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
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TempSensor
STH11
based

App
(SW)
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
P
A
L
<use>
<use>
<use>
PAL
IMPLEMENTATION
(MCUx)
implements
MCU FW
COMPONENTS
IMPLEMENTATION
(HWy)
implements
<use>
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
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TempSensor
STH11
based

App
(SW)
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
P
A
L
<use>
<use>
<use>
PAL
IMPLEMENTATION
(MCUx)
implements
MCU FW
COMPONENTS
IMPLEMENTATION
(HWy)
implements
TempSensor
STH11
based
<use>
PCB
Components
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
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App
(SW)
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
COMPONENTS
IMPLEMENTATION
(HWy)
Components
Factory
P
A
L
<use>
<use>
<use>
<use>
<use>
PAL
IMPLEMENTATION
(MCUx)
<use>
MCU FW
<use>
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
Making It Right: Final architecture
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Making It Right: Let’s for business
BUSINESS
APPLICATION
DEVELOPMENT
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ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
Components
Factory
P
A
L
<use>
PAL
IMPLEMENTATION
(MCUx)
S
Y
S
C
O
M
P
O
N
E
N
T
S
I
M
P
L
App
(SW)
Test Doubles
MCU FW
Making It Right: Developing Embedded Business Software
Application
Test Suite
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ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
Components
Factory
P
A
L
<use>
PAL
IMPLEMENTATION
(MCUx)
S
Y
S
C
O
M
P
O
N
E
N
T
S
I
M
P
L
Test Doubles
MCU FW
Application
Test Suite
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ARRANGE
SYSTEM ARRANGES
App
(SW)

ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
Components
Factory
P
A
L
<use>
PAL
IMPLEMENTATION
(MCUx)
S
Y
S
C
O
M
P
O
N
E
N
T
S
I
M
P
L
Test Doubles
MCU FW
Application
Test Suite
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ARRANGE
SYSTEM ARRANGES
SYSTEM x
ARRANGES
App
(SW)

ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
Components
Factory
P
A
L
<use>
PAL
IMPLEMENTATION
(MCUx)
S
Y
S
C
O
M
P
O
N
E
N
T
S
I
M
P
L
Test Doubles
MCU FW
Application
Test Suite
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ARRANGE
SYSTEM ARRANGES
SYSTEM x
ARRANGES <instantiate>
App
(SW)

ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
Components
Factory
P
A
L
<use>
PAL
IMPLEMENTATION
(MCUx)
S
Y
S
C
O
M
P
O
N
E
N
T
S
I
M
P
L
Test Doubles
MCU FW
Application
Test Suite
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App
Test-
Instrumented
ARRANGE
App
(SW)
ARRANGE
SYSTEM ARRANGES
SYSTEM x

ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
Components
Factory
P
A
L
<use>
PAL
IMPLEMENTATION
(MCUx)
S
Y
S
C
O
M
P
O
N
E
N
T
S
I
M
P
L
SYSTEM ASSERTS
ASSERT
Test Doubles
MCU FW
Application
Test Suite
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App
Test-
Instrumented
ARRANGE
ARRANGE
SYSTEM ARRANGES
App
(SW)
SYSTEM x

ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
Components
Factory
P
A
L
<use>
PAL
IMPLEMENTATION
(MCUx)
S
Y
S
C
O
M
P
O
N
E
N
T
S
I
M
P
L
App
(SW)
SYSTEM ASSERTS
ASSERT
Test Doubles
MCU FW
Application
Test Suite
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SYSTEM x
ASSERTS
App
Test-
Instrumented
ARRANGE
ARRANGE
SYSTEM ARRANGES
SYSTEM x

ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
Components
Factory
P
A
L
<use>
PAL
IMPLEMENTATION
(MCUx)
S
Y
S
C
O
M
P
O
N
E
N
T
S
I
M
P
L
App
(SW)
SYSTEM ASSERTS
ASSERT
Test Doubles
MCU FW
Application
Test Suite
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SYSTEM x
ASSERTS
App
Test-
Instrumented
ARRANGE
ARRANGE
SYSTEM ARRANGES
SYSTEM x
<use>

ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
Components
Factory
P
A
L
<use>
PAL
IMPLEMENTATION
(MCUx)
S
Y
S
C
O
M
P
O
N
E
N
T
S
I
M
P
L
SYSTEM ASSERTS
ASSERT
Test Doubles
MCU FW
Application
Test Suite
.francliment.com
SYSTEM x
ASSERTS <use>
App
Test-
Instrumented
ARRANGE
ARRANGE
SYSTEM ARRANGES
SYSTEM x
App
(SW)
ACT

ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
Components
Factory
P
A
L
<use>
PAL
IMPLEMENTATION
(MCUx)
ARRANGE
App
Test-
Instrumented
S
Y
S
C
O
M
P
O
N
E
N
T
S
I
M
P
L
ARRANGE
ACT
App
(SW)
SYSTEM ASSERTS
SYSTEM ARRANGES
SYSTEM x
ARRANGES
ASSERT
SYSTEM x
ASSERTS
Test Doubles
<instantiate>
Unit of Functionality 1
MCU FW
Application
Test Suite
.francliment.com
<use>

ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
Components
Factory
P
A
L
<use>
PAL
IMPLEMENTATION
(MCUx)
ARRANGE
App
Test-
Instrumented
S
Y
S
C
O
M
P
O
N
E
N
T
S
I
M
P
L
ARRANGE
ACT
App
(SW)
SYSTEM ASSERTS
SYSTEM ARRANGES
SYSTEM x
ARRANGES
ASSERT
SYSTEM x
ASSERTS
Test Doubles
<instantiate>
MCU FW
Application
Test Suite
.francliment.com
<use>

ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
Components
Factory
P
A
L
<use>
PAL
IMPLEMENTATION
(MCUx)
ARRANGE
App
Test-
Instrumented
S
Y
S
C
O
M
P
O
N
E
N
T
S
I
M
P
L
ARRANGE
ACT
App
(SW)
SYSTEM ASSERTS
SYSTEM ARRANGES
SYSTEM x
ARRANGES
ASSERT
Unit of Functionality N
SYSTEM x
ASSERTS
…
Test Doubles
<instantiate>
MCU FW
Application
Test Suite
.francliment.com
<use>

.francliment.com
Takeaways: Application test suite goals
Application test suite GOALS
Capture product specifications, allowing:
▪ Implement them without introducing errors.
▪ Implement them safely and incrementally.
▪ Specify them for different system or product configurations.
▪ Hardware Bottleneck related uncertainties and delays removal.
▪ Any type: functional, load, performance…

Making It Right: Application test example
.francliment.com

.francliment.com
System Arranges API

.francliment.com
HVAC System based variant assert

.francliment.com
O D
HVAC System based variant assert

.francliment.com
System Asserts API

App
(SW)
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
Software (99%)
I
C
D
R
I
V
E
R
S
COMPONENTS
IMPLEMENTATION
(HWy)
Components
Factory
P
A
L
<use>
<use>
<use>
<use>
<use>
PAL
IMPLEMENTATION
(MCUx)
<use>
MCU FW
<use>
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
.francliment.com
Plugin Architecture

App
(SW)
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
COMPONENTS
IMPLEMENTATION
(HWy)
Components
Factory
P
A
L
<use>
<use>
<use>
<use>
<use>
<use>
PAL
IMPLEMENTATION
(MCUx)
implements
MCU FW
implements
Software (99%)
<use>
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
Plugin Architecture
.francliment.com

Software (99%)
ADCs
SFRs
SPECIAL
FUNCTION
REGISTERS
GPIOs
SFRs
TMRs
SFRs
I2Cs
SFRs
SPIs
SFRs
App
(SW)
S
Y
S
T
E
M
C
O
M
P
O
N
E
N
T
S
HW
MCU FW
HARDWARE
ABSTRACTION
BUSSINESS
LOGIC
I
C
D
R
I
V
E
R
S
COMPONENTS
IMPLEMENTATION
(HWy)
Components
Factory
P
A
L
<use>
<use>
<use>
<use>
<use>
PAL
IMPLEMENTATION
(MCUx)
implements
PLUGIN
TO BUSSINESS LOGIC
implements
<use>
<use>
.francliment.com
Plugin Architecture

.francliment.com
“FINAL BONUSES

.francliment.com
“Debugging is part of development”
Fallacies & Mantras: Debugging

.francliment.com
“Debugging is part of development”
Debugging is a SHAME!
While debugging we are not creating anything
new: we are adding zero value to our
organization
Fallacies & Mantras: Debugging

.francliment.com
Takeaways: Measure, locate and remove real bottlenecks
Measure your lead time in
order to objectively know
which are your bottlenecks

.francliment.com
“TDD is a testing technique”
Fallacies & Mantras: TDD as testing activity

.francliment.com
Takea-way: TDD is not a testing activity
TDD is a design and
development technique

.francliment.com
“TDD is for Unit testing only”
Falacies & Mantras: TDD is for unit testing

.francliment.com
“The Unit Under Test is a class
or a method”
Falacies & Mantras: The UNITY concept

.francliment.com
Takeaways: Units of behaviour
The Unit Under Test must always
be an external observable
behavior

We can’t be Agile if
our code sucks!
.francliment.com
Takeaways: Beware of Flacid Agile

We can’t improve
our code if we fear
to refactor it
.francliment.com
Takeaways: Acquired Incompetence

We can’t fearless refactor it
without a comprehensive
suite of automated tests
.francliment.com
Takeaways: Comprehensive safety net

“Raise your quality standards as high as you
can live with, avoid wasting your time on routine problems, and always try
to work as closely as possible at the boundary of your abilities. Do this, because
it is the only way of discovering how that
boundary should be moved forward”
.francliment.com
Takeaways: Continuous improvement
― Edsger W. Dijkstra

Thanks
GRACIAS
.francliment.com
@fraclipe
@FranciscoClimentPerez

Embo++2022 Unembedding Embedded Systems with TDD Benefits of going beyond the Make-It-Work phase.pdf

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