Metal-In Test-Driven Development_A Dual-Target TDD Approach (NDC TechTown 2024).pdf

Metal-In Test-Driven Development: A Dual-Target TDD Approach.
Slides of my practical talk about how to apply TDD to embedded, delivered at NDC TecthTown 2024 conference. It deals with how to expand TDD to cover units of behavior from metal-to-metal, ie, from uC inputs till its outputs.

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Metal-In Test-Driven Development
A Dual-Target TDD Approach
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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Me
•Senior R&D Software Developer @ Kongsberg Discovery Spain
•Technical Agile Coach @ francliment.com
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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Me
•Senior R&D Software Developer @ Kongsberg Discovery Spain
•Technical Agile Coach @ francliment.com
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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francliment.comNDC TechTown 2024 Metal-In TDD: A Dual-Target Approach
We are hiring!

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Why this talk?
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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Unembedding Embedded
Systems with TDD:
Benefits of Going Beyond The
Make-It-Work Phase
A ‘practical’ companion talk
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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Getting Feedback from the
Metal/Hardware
(an easy example)

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How could we assure the code does really turn On& Offan LED?
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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Measure
voltage at
GPIO output
Measuring the
current loop
Use Logic
analyzer
(assuring logic
levels & timing)
Use some kind of
photodetector
How could we assure the code does really turn On& Offan LED?

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

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Main Goal:
-Make possible to create and evolve any embedded codeaspect MUCHfaster and
safer, iteratively and incrementally.
‘Metal-In’ Development Approach

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How:
Main Goal:
-Continuously looking for ways to get feedback faster.
-Make possible to create and evolve any embedded codeaspect MUCHfaster and
safer, iteratively and incrementally.
‘Metal-In’ Development Approach

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How:
Main Goal:
-Continuously looking for ways to get feedback faster.
-Treating as much embedded codeas possible as a ‘independent’ subsystem.
-Make possible to create and evolve any embedded codeaspect MUCHfaster and
safer, iteratively and incrementally.
‘Metal-In’ Development Approach

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How could we assure the code does really turn On& Offan LED?
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach
Measure
voltage at
GPIO output
Measuring the
current loop
Use Logic
analyzer
(assuring logic
levels &
timing)
Use a camera or
another kind of
photodetector
Embedded code actionable area

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How:
Main Goal:
-Make possible to create and evolve any embedded codeaspect faster and safer,
iteratively and incrementally.
-Continuously looking for ways to get feedback faster.
-Treating as much embedded codeas possible as a ‘independent’ subsystem.
-Whenever possible, promoteusing cheap SIL (aka software test-doubles) instead of any
kind of HIL.
‘Metal-In’ Development Approach

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Nothing happens ‘outside’
if it doesn’t change an SFR bit
‘Metal-In’ Development Approach

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‘Metal-In’ Development Approach
How:
Main Goal:
Business outcome:
-Increasedembedded software development lead time.
-Sustainable development pace.
-Make possible to create and evolve any embedded codeaspect faster and safer,
iteratively and incrementally.
-Continuously looking for ways to get feedback faster.
-Treating as much embedded codeas possible as a ‘independent’ subsystem.
-Whenever possible, promoteusing cheap SIL (aka software test-doubles) instead of any
kind of HIL.

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1. Make It Work
3. Make It Fast (enough)
2. Make It Right (enough)
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
Focused in understanding how to solve the problem, not about
engineering the code right
Fulfill system timing requirements
Evolutive Design & Development
Engineer and craft the code right to make it easy to understand,
maintain and evolve
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Red
GreenRefactor
Make It Work
Make It Right
Test code only
KISS : Keep it Simple, Stupid
1
DRY : Don’t Repeat Yourself
1
2
Production code only
1
Simple Design,
SOLID,
Design Patterns…
2
DAMP : Descriptive And
Maintainable Procedures
Evolutive Design & Development: TDD Implementation
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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Embedded TDD cycle
Embedded software as complete subsystem
(End-to-end == from metal-to metal)
Metal-In Test-Driven Development: A Dual-Target TDD approach
HOSTTARGET
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach
Source: ‘Test-Driven Development for Embedded C’ book, James W. Grenning
Integration ‘datasheet
interpretation’ tests

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MCU
FW
The Embedded (“Morse-ish”) Hello world

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Practical Example (KATA): 4-Level Battery Monitor
•(Current)Microcontroller:MicrochipPIC18F47K40(8-bitbaremetal).
•(Current)Hardwarevariant:4StatusLEDsconnectedtoPORTA’shighnibble.
•Katacontext:
▪FirstinternalMCUusage(noPALimplementationavailableyet).
▪‘BatteryStatusPercentageProvider’moduleisunderdevelopmentbyanother
team.
•Kataobjective:
▪Developahighlydecoupledandportable‘BatteryMonitor’modulefollowing
Metal-InTest-DrivenDevelopment.
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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Dual-Target Development Environment
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach
Vendor agnostic tools (Current) Vendor dependant tools
•Lightweightedunittesting&
buildsystemforC.
•Automated test-double
creation.
•Used on HOST set-up
•Related tools: Gcov
•Used on TARGET set-up
•Related tools: XC8 &Microchip Debugger
(MDB)
+
•(Current) Hardware variant
•State-of-the-art
automatedrefactoring
features.

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MCU
FW
Datasheet:
A written on (silicon)stone contract

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PIC18F47K40: Commanding GPIOs
Example:CommandA7GPIOstate
▪WritetoPORTAbit7(orLATAbit7)
A7
TRISA7
ANSELA7
Read LATA7
Read PORTA7
Write LATA7
Write PORTA7
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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PIC18F47K40: Commanding GPIOs
Example:CommandA7GPIOstate
▪WritetoPORTAbit7(orLATAbit7)
A7
TRISA7
ANSELA7
Read LATA7
Read PORTA7
Write LATA7
Write PORTA7
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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PIC18F47K40: Commanding GPIOs
Example:ReadA7GPIOstate
▪ReadfromPORTAbit7
A7
TRISA7
ANSELA7
Read LATA7
Read PORTA7
Write LATA7
Write PORTA7
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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PIC18F47K40: Commanding GPIOs
Example:ReadA7GPIOstate
▪ReadfromPORTAbit7
A7
TRISA7
ANSELA7
Read LATA7
Read PORTA7
Write LATA7
Write PORTA7
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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1

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PIC18F47K40: GPIO Reset Configuration
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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1)TRISAbit7toLOW(meansoutputdriverenabled)
ConfiguringA7GPIOasOUTPUT:
PIC18F47K40: GPIO Configuration
PORTA7
TRISA7
ANSELA7
Read LATA7
Read PORTA7
Write LATA7
Write PORTA7
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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A7
TRISA7
ANSELA7
Read LATA7
Read PORTA7
Write LATA7
Write PORTA7
1)TRISAbit7toLOW(meansoutputdriverenabled)
ConfiguringA7GPIOasOUTPUT:
PIC18F47K40: GPIO Configuration
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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1)TRISAbit7toLOW(meansoutputdriverenabled)
ConfiguringA7GPIOasOUTPUT:
PIC18F47K40: GPIO Configuration
2)ANSELAbit7toLOW(inputbuffersenabled)
A7
TRISA7
ANSELA7
Read LATA7
Read PORTA7
Write LATA7
Write PORTA7
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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1)TRISAbit7toLOW(meansoutputdriverenabled)
ConfiguringA7GPIOasOUTPUT:
PIC18F47K40: GPIO Configuration
2)ANSELAbit7toLOW(inputbuffersenabled)
A7
TRISA7
ANSELA7
Read LATA7
Read PORTA7
Write LATA7
Write PORTA7
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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2

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Red
GreenRefactor
Make It Work
Make It Right
Test code only
KISS : Keep it Simple, Stupid
1
DRY : Don’t Repeat Yourself
1
2
Production code only
1
Simple Design,
SOLID,
Design Patterns…
2
DAMP : Descriptive And
Maintainable Procedures
Reaching the RED: Assuring the Hardware/Metal works on purpose
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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3

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Red
GreenRefactor
Make It Work
Make It Right
Test code only
KISS : Keep it Simple, Stupid
1
DRY : Don’t Repeat Yourself
1
2
Production code only
1
Simple Design,
SOLID,
Design Patterns…
2
DAMP : Descriptive And
Maintainable Procedures
Made-It-Work: ‘Datasheet ContratInterpretation’ acceptance test passed
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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Red
GreenRefactor
Make It Work
Make It Right
Test code only
KISS : Keep it Simple, Stupid
1
DRY : Don’t Repeat Yourself
1
2
Production code only
1
Simple Design,
SOLID,
Design Patterns…
2
DAMP : Descriptive And
Maintainable Procedures
Make-It-Right: Time to engineer the code right
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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Red
GreenRefactor
Make It Work
Make It Right
Next self-checking specification: a complete micro-cycle in action
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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5

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OnlywhenrunningonTARGET
TARGET run: Round 1
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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OnlywhenrunningonTARGET
TARGET run: Round 1
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach
MCU
FW
MCU
FW

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6

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Red
GreenRefactor
Make It Work
Make It Right
Test code only
KISS : Keep it Simple, Stupid
1
DRY : Don’t Repeat Yourself
1
2
Production code only
1
Simple Design,
SOLID,
Design Patterns…
2
DAMP : Descriptive And
Maintainable Procedures
Make-It-Right: Time to engineer the code right
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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7

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OnlywhenrunningonTARGET
TARGET run: Round 2. Collaborator
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach
MCU
FW
MCU
FW

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Only when
running on
HOST
HOST run: ‘Tied’ to the running MCU
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach
MCU
FW
MCU
FW

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Only when
running on
HOST
HOST run: ‘Tied’ to the running MCU
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach
MCU
FW
MCU
FW

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Current production code:
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach

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MCU
FW
First make the change easy,
then make the easy change.

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10

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MCU
FW
First make the change easy,
then make the easy change.

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HOST run: Production code decoupled from the running MCU
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach
MCU
FW

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TARGET run: Production code decoupled from the running MCU
NDC TechTown 2024 Metal-In TDD: A Dual-Target Approach
MCU
FW

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INCOMPLETENESS

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BatteryMonitor_Init(unit8_t StatusLED1_GPIOId,
unit8_t StatusLED2 _GPIOId,
unit8_t StatusLED3 _GPIOId,
unit8_t StatusLED4 _GPIOId);

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PAL_GPIO partially implemented

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PAL_GPIO partially implemented
Test-Driving it through
test_PAL_GPIO

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Neo:
Morpheus:
What are you trying to tell me? That I can dodge bullets?
No, Neo. I'm trying to tell you that when you're ready, you won't have to.

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GRACIAS

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Neo:
Morpheus:
Q&A