Bare-Metal STM32: Exploring Memory-Mapped I/O And Linker Scripts

December 23, 2020 by Maya Posch 19 Comments

In the first installment of this series we had a brief look at the steps needed to get a bare-metal application running on an STM32 microcontroller. While this allowed us to quickly get to the juicy stuff, there are two essential elements which make an MCU so easy to use. One is found on the hardware side, in the form of so-called memory-mapped I/O (input/output), the other is the information contained in the files that are passed to the linker when we build a firmware image.

Memory-mapping of hardware peripheral registers is a straightforward way to make them accessible to the processor core, as each register is accessible as a memory address. This is both convenient when writing the firmware code, as well as for testing, as we can use a memory mapping specific for unit or integration testing.

We will take an in-depth look at this way of testing, as well as how these linker script files are connected to the memory layout. Continue reading “Bare-Metal STM32: Exploring Memory-Mapped I/O And Linker Scripts” →

PS2 Emulation On The Xbox Series S: A Story Of Walled Gardens

December 15, 2020 by Maya Posch 25 Comments

It’s hardly a secret any more at this point that today’s game consoles from Microsoft and Sony are essentially AMD gaming rigs packed up into a custom package and with tweaked system software. So it’s not too surprising that enterprising hackers got the Playstation 2 emulator of RetroArch running on an Xbox Series X|S game console despite Microsoft’s attempts to stop them. (Video, embedded below.)

It’s possible to sneak the RetroArch app past Microsoft’s security checkpoints by shelling out $19 for a Microsoft Developer Account, setting up Developer Mode on the XBox console, and getting the Universal Windows Platform (UWP) port of RetroArch from the official website. This has the advantage of it being a blessed-by-the-Redmond-gods approach. But one cannot play retail games in Developer Mode and large games due to a 2 GB limit.

More recently, a hacker by the name of [tunip3] found a flaw in the Xbox app distribution system which allows one to download a ‘retail’ version of RetroArch. This involves marking the RetroArch app as ‘private’, allowing it to skip a review by Microsoft. People whose email address is on a whitelist are then granted download permission for that app on their Xbox console. The advantage of this ‘retail’ approach is that it does not feature the 2 GB filesize limits. The disadvantage is that Microsoft is free to take the app down and ban [tunip3]’s developer account.

My Way Versus the Highway

A lot about this comes down to a simple question of ‘why?’. Why even jump through these hoops to set up a limited, possibly ToS-breaking emulator on what is ultimately a gaming PC running Windows 10? Why not use that Raspberry Pi 4 or NUC system that’s been giving you sad eyes for the past months from where it’s been stuffed into a dusty corner?

Continue reading “PS2 Emulation On The Xbox Series S: A Story Of Walled Gardens” →

Bare-Metal STM32: Blinky And The Secret Of Delay Functions

December 11, 2020 by Maya Posch 35 Comments

One of the very first examples for an MCU or SoC usually involves the famous ‘Blinky‘ example, where an LED is pulsed on and off with a fixed delay. This is actually a lot more complicated than the ‘Pushy‘ example which we looked at in the first installment of this series. The reason for this is that there’s actually quite a story behind a simple call to delay() or its equivalent.

The reason for this is that there are many ways to implement a delay function on a microcontroller (MCU), each of which comes with their own advantages and disadvantages. On an STM32 MCU, we get to choose between essentially an active delay (while loop), one implemented using the SysTick timer and using one of the peripheral timers. In the latter two cases we also have to use interrupts.

In this article we’ll take a look at all three approaches, along with their advantages and disadvantages.

Continue reading “Bare-Metal STM32: Blinky And The Secret Of Delay Functions” →

Remembering Chuck Yeager: The Supersonic Legend Whose Wings Were Clipped By A High School Diploma

December 10, 2020 by Maya Posch 37 Comments

In history there are people whose legacy becomes larger than life. Ask anyone who built and flew the first airplane, and you’d be hard-pressed to find someone who isn’t at least aware of the accomplishments of the Wright brothers. In a similar vein, Chuck Yeager’s pioneering trip into supersonic territory with the Bell X-1 airplane made his name essentially synonymous with the whole concept of flying faster than the speed of sound. This wasn’t the sole thing he did, of course: he also fought in WWII and Vietnam and worked as an instructor and test pilot, flying hundreds of different airplanes during his career.

Yeager’s insistence on making that first supersonic flight, despite having broken two ribs days earlier, became emblematic of the man himself: someone who never let challenges keep him from exploring the limits of the countless aircraft he flew, while inspiring others to give it their best shot. Perhaps ironically, it could be said that the only thing that ever held Yeager back was only having a high school diploma.

On December 7, 2020, Chuck Yeager died at the age of 97, leaving behind a legacy that will continue to inspire many for decades to come.

Continue reading “Remembering Chuck Yeager: The Supersonic Legend Whose Wings Were Clipped By A High School Diploma” →

Incredible Discrete MOSFET Rover Has Maximum Blink

December 4, 2020 by Maya Posch 12 Comments

What do you get when you stick 1738 MOSFETs together? If your answer was a ‘4-bit CPU’, you would be totally correct. Available as a product over at Marutsu as the ‘CPU1738’, it seems to target beginners to computer theory, with build instructions that explain how the CPU is built up from individual MOSFETs that are combined into logic gates.

While decidedly more compact in its SMD format than it would have been with pure through-hole parts, the use of countless small PCBs on top of the larger PCBs make for a pretty hefty package. Board after board build up the CPU, and the assembly continues with the addition of sensors, motors, and wheels. In the end, a robot emerges, albeit a somewhat wobbly-looking one.

Check out the video linked after the break, though before starting one up, note the 50,000 Yen (approximately $500) price tag for the CPU block alone. On the other hand, in addition to the 1738 MOSFETs, there are also 1070 LEDs, so you get what you pay for in blinkies.

Continue reading “Incredible Discrete MOSFET Rover Has Maximum Blink” →

FTDI VCP Chips With Custom PIDs Not Working On MacOS 11 Big Sur

December 3, 2020 by Maya Posch 49 Comments

An anonymous reader pinged us about an issue that affects people who jumped onto the latest-and-greatest OS from the Apple gardens: USB devices that stop working due to the FTDI-based USB solution. At its core appears to be that the built-in FTDI driver provided by Apple (AppleUSBFTDI.dext) only supports FTDI chips which provide the standard FTDI vendor and product ID (e.g. 0x0403 and 0x6001 respectively for the FT232R). Many products however set a custom product ID (PID) to differentiate their device, though in the thread some mention that there are driver issues even with the default VID/PID combination.

Over the past years, Apple has been restricting and changing the way kernel extensions (KExt) and driver extensions (DExt) are handled. As these FTDI chips are often used for virtual com port (VCP) purposes, such as with Arduino boards and USB-TTL adapters, this is a rather cumbersome issue that would affect anyone using Big Sur in combination with such a hardware device.

So far only the FTDI team has been somewhat responsive based on the support forum thread, with Apple seemingly rather silent on the issue.

Game Cartridges And The Technology To Make Data Last Forever

December 3, 2020 by Maya Posch 69 Comments

Game cartridges are perhaps the hardiest of all common storage schemes. Short of blunt traumatic force or application of electrical surges to the cartridge’s edge connectors, damaging a game cartridge is hard to do by accident. The same is also true for the data on them, whether one talks about an Atari 2006 cartridge from the late 1970s or a 1990s Nintendo 64 cartridge.

The secret sauce here are mask ROMs (MROM), which are read-only memory chips that literally have the software turned into a hardware memory device. A mask layer unique to each data set is used when metalizing the interconnects during chip fabrication. This means that the data stored on them is as durable as the processor in the game console itself. Yet this is not a technology that we can use in our own hobby projects, and it’s not available for personal long-term data storage due to the costs associated with manufacturing what is essentially a custom chip.

Despite its value as truly persistent storage, MROM has fallen out of favor over the decades. You may be surprised to find a lot of what’s currently used in the consumer market is prone to data corruption over time spans as short as one year to one decade depending on environmental conditions.

So what are we to do if we need to have read-only data that should remain readable for the coming decades?

Continue reading “Game Cartridges And The Technology To Make Data Last Forever” →