Reading the STM32 unique device ID in C

All STM32 microcontrollers feature a 96-bit factory-programmed unique device ID. However, for me it was hard to find an adequately licensed example on how to read it in a manner compatible with different families and compilers.

Here’s a simple header that defines a macro for the device ID address. While I checked the address for both STM32F4 and STM32F0 families, other families might have slightly different addresses for the device ID. Check the reference manual corresponding to your STM32 family if errors occur.

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Posted by Uli Köhler in C/C++, Embedded

Reading STM32F0 internal temperature and voltage using ChibiOS

The STM32F0 series of 32-bit ARM Cortex M0 microcontrollers contain a huge number of internal peripherals despite their low price starting at 0,32€ @1pc. Amongst them is an internal, factory-calibrated temperature sensor and a supply voltage sensor (that specifically senses VDDA, the analog supply voltage rail) connect to channels 16 and 17 of the internal ADC.

While I usually like the STM32 documentation, it was quite hard to implement code that produced realistic values. While the STM32F0 reference manual contains both formulas and a short section of example code, I believe that some aspects of the calculation are understated in the computation:

Section 13.9 in RM0091 provides a formula for computing the temperature from the raw temperature sensor output and the factory calibration values. However it is not stated anywhere (at least in Rev7, the current RM0091 revision) that this formula is only correct for a VDDA of exactly 3.30V.

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Posted by Uli Köhler in C/C++, Embedded

Fixing bad blocks on HDDs using


You hard drive or SMART tool reports errors when reading specific blocks similar to this message:

[3142.686141] end_request: I/O error, dev sda, sector 31415926

No matter how often you read the block, the hard drive still returns an error and does not reallocate the block.

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Posted by Uli Köhler in Linux, Python

Listing files inside a Torrent

Torrent files are essentially containers that store information about a set of files to be downloaded via P2P.

Unfortunately it is not easily possible to simply list the files that are stored in a torrent. Using our python script you can easily accomplish that task.

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Posted by Uli Köhler in Python

Reading the UniProt text format in Python

Just like many other databases in computational biology, the downloads for the popular UniProt database are available in a custom text format which is documented on ExPASy.

While it is certainly not difficult writing a generic parser and one can use BioPython, I believe it is often easier to use a tested parser that only uses standard libraries.

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Posted by Uli Köhler in Bioinformatics, Python

Using the lwIP SNTP client with ChibiOS

A common task with embedded systems is to use the RTC to timestamp events. However, the system architect needs to find a way of synchronizing the devices RTC time with an external time source. Additionally, the designer needs to deal with the problem of drifting RTC clocks, especially for long-running devices. This article discusses an lwIP+SNTP-based approach for STM32 devices using the ChibiOS RTOS. The lwIP-specific part of this article is also applicable to other types of microcontrollers.

For high-accuracy or long-running applications, RTC clock drift also has to be taken into account. Depending on the clock source in use, the clock frequency can deviate significantly from the nominal value.

On the STM32F4 for example, you can derive the RTC clock from: The HSE/HSI main oscillator The LSI oscillator * The LSE oscillator, i.e. a 32.768 kHz external crystal.

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Posted by Uli Köhler in C/C++, Embedded

Enforcing debugger breakpoints in ChibiOS chDbgAssert()

ChibiOS provides a variety of debug functions that can be enabled or disabled using preprocessor definitions.

When debugging ARM-based microcontrollers like the STM32, it can be useful to hardcode

This post provides a simple method of improving the definition of chDbgAssert() in chdebug.h so that a breakpoint is enforced in case of assertion failures. By using the ARM BKPT instruction, the overhead is only a single assembler instruction.

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Posted by Uli Köhler in Embedded

Reading STM32 unique device ID using OpenOCD

When working with the STM32 family of microcontrollers, it can be useful to evaluate the factory-programmed 96-bit UUID using JTAG. On all major operating systems, OpenOCD provides a simple yet highly compatible and free solution in order to do this.

In this example, we’ll use a JLink adapter together with the Olimex E407 evalation board. Both the adapter and the board are interchangable, provided you have working OpenOCD configurations available.

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Posted by Uli Köhler in Embedded

Extracting open library author names using Haskell Conduits

Almost anyone productively using Haskell has already stumbled upon Michael Snoyman’s Conduit library.

In this post I will show how to leverage the power of Conduit interleaved IO in order to parse author’s names from the Open Library data dumps.

Using traditional languages like Java or C, it would be significantly more difficult and error-prone to interleave the processing pipeline actions of

  • Downloading the file ol_dump_authors_latest.txt.gz using HTTP
  • Decompressing using a gunzip-like function
  • Splitting into lines and discarding everything but the JSON from said lines
  • Appropriately decoding the JSON and extracing the name field, or ignoring the line if parsing is not possible
  • Writing all said names into a files (authors.txt in this example), one per line.

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Posted by Uli Köhler in Haskell

Yet another Atom Arduino blinker

While experimenting with Atom I produced a minimal example for making my old Arduino Uno blink its LED periodically.

Although there are plenty of examples out there (some of them even work!) I didn’t want to introduce any dependency to the Arduino libraries. Besides making it harder to build (even if arscons is quite nice) it increases the object size and Arduino only supports a limited range of processors. I need the flexibility to use the code on controlles like the ATTiny45

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Posted by Uli Köhler in Allgemein, Embedded

Using QuasiQuotation for more readable Atom code

Lately I’ve been experimenting with using Atom to generate intrinsically reliable embedded software.

In contrast to alternatives like Copilot in Atom you include the surrounding C code as Haskell strings whereas other concepts just generate a set of C files to include in your main code.

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Posted by Uli Köhler in Haskell

How I solved my Toshiba Linux backlight issues


I have both the Toshiba Z830 and R850 for a couple of years now. On both, I’m using the current LTS versions of KUbuntu (at the time of writing this, 14.04). Although, I’m absolutely satisfied with them, there’s a little issue regarding the backlight:

On startup, the backlight works perfectly well. I can change the settings using FN+F6/F7 without any issues. However, after putting the device into standby and waking it up again, pressing said hotkeys shows the backlight percentage dialog, but does not change the brightness.

Because Ubuntu’s SSD reboots are pretty fast Iimply didn’t care about the issue for the past few years. However, out of curiosity, I successfully fixed the issue today.

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Posted by Uli Köhler in Linux

Parsing the OUI database in Haskell

In this post, we will show a method and provide a Haskell module capable of parsing both the IEEE OUI list and the IEEE IAB list.

While our code only parses the databases into an object form and doesn’t insert them into a tree capable of fast MAC address -> vendor lookup, it is based on Attoparsec, providing good performance and high flexibility for changes.

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Posted by Uli Köhler in Haskell