The document discusses the Ada Drivers Library, an open source project that provides Ada drivers for interfacing with peripherals on ARM microcontrollers. It aims to demonstrate how Ada's type safety, contract-based programming, and object-oriented features help write clean and reusable device drivers. The library supports various microcontrollers and boards, and provides drivers for peripherals like GPIOs, I2C, SPI, timers. It also includes examples of maker projects built with the library.

2. Senior Software Engineer
Making the Ada Drivers Library
Fabien Chouteau

4. Ada & Device Drivers:
A Well-Engineered Collaboration
Ada’s strong typing system
encourages communication and demands precision
Representation clauses
are the killer feature for coding drivers
Contract-based programming
helps eliminate problems earlier in the development cycle
Object-oriented features
can improve code reuse
Multitasking support
is available for bare metal platforms

5. We wanted to experiment.
So, we started this project as a proof of concept to
explore whether this was demonstrable with modern ARM
microcontrollers.
We wanted to use the best features of Ada to provide:
• clean hardware mapping,
• good interfaces,
• code reuse, and
• easy debugging.

6. What did we learn?
• Modern microcontrollers are gigantic beasts.
• Accessing memory mapped register can be tricky (pragma
Volatile_Full_Access).
• Customization of run-times is still not flexible enough.
• Confirmed that Ada had good properties for programming device
drivers.

7. Representation clauses
GPIO->MODER &= ~(GPIO_MODER_MODER0 << (pin_nbr* 2));
VS
GPIO.MODER.Arr (Pin_Nbr) := 0;

8. package STM32_SVD.RNG is
pragma Preelaborate;
---------------
-- Registers --
---------------
-- control register
type CR_Register is record
-- unspecified
Reserved_0_1 : HAL.UInt2 := 16#0#;
-- Random number generator enable
RNGEN : Boolean := False;
-- Interrupt enable
IE : Boolean := False;
-- unspecified
Reserved_4_31 : HAL.UInt28 := 16#0#;
end record
with Volatile_Full_Access, Size => 32,
Bit_Order => System.Low_Order_First;
for CR_Register use record
Reserved_0_1 at 0 range 0 .. 1;
RNGEN at 0 range 2 .. 2;
IE at 0 range 3 .. 3;
Reserved_4_31 at 0 range 4 .. 31;
end record;
SVD2ada: generating hardware
register mapping

9. <?xml version="1.0" encoding="utf-8" standalone="no"?>
<device schemaVersion="1.1"
xmlns:xs="http://www.w3.org/2001/XMLSchema-instance"
xs:noNamespaceSchemaLocation="CMSIS-SVD_Schema_1_1.xsd">
<name>STM32F46_79x</name>
<version>1.0</version>
<description>STM32F46_79x</description>
<!--Bus Interface Properties-->
<!--Cortex-M4 is byte addressable-->
<addressUnitBits>8</addressUnitBits>
<!--the maximum data bit width accessible within a single transfer-->
<width>32</width>
<!--Register Default Properties-->
<size>0x20</size>
<resetValue>0x0</resetValue>
<resetMask>0xFFFFFFFF</resetMask>
<peripherals>
<peripheral>
<name>RNG</name>
<description>Random number generator</description>
<groupName>RNG</groupName>
<baseAddress>0x50060800</baseAddress>
<addressBlock>
<offset>0x0</offset>
<size>0x400</size>
<usage>registers</usage>
</addressBlock>
<interrupt>
<name>HASH_RNG</name>
SVD2ada: generating hardware
register mapping

10. Now what?

11. Introducing the Ada_Drivers_Library
An Open Community Project hosted on GitHub
Vendor-independent
Makes it easy to use Ada to do interesting things with a
variety of ARM microcontrollers!

12. Ada_Drivers_Library Framework
MCU
HAL
Components
Services
Low-level drivers to interface with
peripherals on particular
microcontrollers
Ada layer providing clean
abstraction of hardware
External components connected to
the MCU in a standard way (I2C,
UART, SPI, SDIO, MMC, etc.)
OS services (we have a filesystem;
on our wishlist is a network stack,
USB stack, Bluetooth, etc.)

13. What’s in it?
• GPIOs
• I2C, SPI, UART
• ADC, DAC
• Audio (SAI)
• LCD and touch screen drivers
• Timers, PWM
• DMA
• Flexible Memory Controller (external RAM)
• Camera (DCMI)
• Random Number Generator
• SDcard

14. On what board?

15. Crazyflie 2.0

16. OpenMV

17. BBC Micro:Bit

18. Roadmap
• More boards from more vendors
• More device drivers
• More services (Filesystem, Bluetooth, USB)
• Robotics utilities and drivers
• General purpose control system code

19. Making with Ada

20. Make with Ada: Candy dispenser, with
a twist

21. Make with Ada: DIY Instant
Camera

22. Make with Ada: ARM
Cortex-M CNC controller

24. More Information Online
• The Ada_Drivers_Library
https://github.com/AdaCore/Ada_Drivers_Library
• Ada Driver Library for ARM Cortex-M/R - Part 1
https://community.arm.com/groups/embedded/blog/2016/07/08/ada-
driver-library
• MCQ Candy Dispenser
http://blog.adacore.com/make-with-ada-candy-dispenser-with-twist
• DIY Instant Camera
https://www.youtube.com/watch?v=MHo5bcHWx3o
• ARM Cortex-M CNC Controller
http://blog.adacore.com/make-with-ada-arm-cortex-m-cnc-controller