Renode

I find it a useful tool. Maybe you will, too!

About Me: I Do Weird Hardware

  • Simmel: Contact Tracing with Audio
  • Chibitronics: Programming Stickers with Audio
  • Novena: Open Source Laptop
  • Senoko: Open Source Power Board for Novena

About Renode

  • Whole-System Emulator
  • Supports concurrent emulation
  • Extensible with C# and Python
  • MIT Licensed
  • Windows, Mac, Linux

About This Talk

  • Overview of Emulators
  • Oevrview of Weird Hardware
  • Cool things you can do

Who will find this interesting?

  • Creators: Those making new boards or hardware
  • Integrators: Running CI on firmware files
  • Reverse Engineers: Understanding new hardware and firmware

Creators: Making New Things!

  • Reusing an existing platform
  • Reusing an existing microcontroller
  • New microcontroller fron existing family

Integrators: Making Sure Nothing Broke!

  • Hardware testing incompatible with cloud
    • ...it sure is effective, though
  • Hardware crunch makes it difficult to get hardware
  • Downloading software is much cheaper than shipping
  • Can run tests on every code push

Reverse Engineers: What Is This Blob Doing?

  • Staring at code flow is enlightening, but time-consuming
  • What is it doing and how does it get there?
  • How can we make it do $x?

What is an Emulator?

  • Console
  • Desktop
  • CPU

Whole-System Emulator

  • Wii Virtual Console
  • VirtualBox
  • Parallels

Transparent Emulator

  • HyperV
  • WSL2/Docker
  • qemu on Linux
  • Rosetta on Mac

Debugger/Emulator

  • FCEUX (Nintendo Entertainment System)
  • Dolphin (Wii / Gamecube)

Renode Is All of These

  • Console: Able to present an interactive environment
  • Transparent: Can run in CI via Robot commands
  • Debugger: Has a GDB server built in

What is a Computer?

Example of Weird Hardware

  • NRF52840
  • LM74 Temperature Sensor

Example of Weird Hardware

  • NRF52833
  • LM74 Temperature Sensor

Example of Weird Hardware

  • BlueNRG1
  • LM74 Temperature Sensor

Example of Weird Hardware

  • RISC-V
  • FPGA-based framebuffer
  • Initial graphical demo in 1 hour

What makes hardware "Weird"?

  • Unusual CPU architecture
  • Different model of chip than commonly found
  • Additional hardware
  • More CPUs per board

Unusual CPU architecture

Sorry, can't help

Different model CPU

  • Maybe it's just a variant
  • Perhaps memory regions were shuffled
  • Does it use the same hardware block as someone else?

New hardware version

  • Do you use the new, specialized features?
  • Lots of UARTs support Infrared. Do you need that?

Completely new hardware

  • Time to break out C#

What is "Firmware"?

How does this interact with $VENDOR_TOOL?

What about boot ROMs?

What about missing registers?

  • Very few projects use built-in blocks

It's All About Small Victories

  • Serial ports are super rewarding
  • They're also usually simple!
  • They are easy to script

Steps to Set Up a Serial Port

  1. Enable peripheral
  2. Set up clock
  3. Mux GPIOs
  4. Calculate baud rate
  5. Write to UART TX register

Steps to Set Up a Serial Port

Advantages of Emulation

Advantages of Emulation

Steps to Set Up a Serial Port

  • Interrupt Support
  • DMA

Example Serial Port


						{(long)Registers.RxTx, new DoubleWordRegister(this)
							.WithValueField(0, 8,
								writeCallback: (_, value) => {
									this.TransmitCharacter((byte)value);
								},
								valueProviderCallback: _ => {
									if(!TryGetCharacter(out var character))
									{
										this.Log(LogLevel.Warning, "Empty Rx FIFO.");
									}
									return character;
								})
						},

Robot Framework: Running Tests in CI


							*** Test Cases ***
							Should Read Acceleration
								Create Machine
								Create Terminal Tester    ${UART}
							
								Execute Command   sysbus.twi1.lis2ds12 AccelerationX 10
								Execute Command   sysbus.twi1.lis2ds12 AccelerationY 5
								Execute Command   sysbus.twi1.lis2ds12 AccelerationZ -5
							
								Start Emulation
							
								Wait For Line On Uart  x 9.997213 , y 4.997410 , z -4.999803

SVD Files

Logging Memory Accesses

Debugging with GDB

Software Assumes Hardware Works

  • Rarely checks for sane ranges (why would you?)
  • TOC-TOU

Incremental Changes

  • Small changes are very rewrding
  • Device will work with only partial implementation