ColdFrame and the micro:bit revisited

This article discusses various issues rebuilding a demonstrator intended for the BBC micro:bit (version 1.3b) after an interval of several years.

Developing for Cortex MCUs on a Raspberry Pi

Recently, on the Gitter Ada Programming Language lobby, there have been discussions on cross-compiling for Cortex M micro-controllers, specifically the BBC micro:bit, using the Raspberry Pi.

TL;DR: it's not going to be easy, unfortunately. Maybe later (or earlier?) Raspbian releases will help.

Using GDB with a BBC micro:bit

This note is about using Segger J-Link software to help debug code on a BBC micro:bit.

MPU9250, continued

This is a note on building support for the MPU9250 9-axis chip in the AdaPilot project (the AdaRacer hardware). It continues this report.

Invensense MPU9250 via SPI

This is a note on building support for the MPU9250 9-axis chip in the AdaPilot project (the AdaRacer hardware; the prototype board I have is subtly different from the one shown).
9-axis means it can measure each of acceleration, gyro and magnetic field values in 3 axes, which is very useful if your drone needs to know about its own motion.

IO Expansion

I started checking out AdaCore's support library for STM32F4 boards, particularly to use I2C to talk to the PCF8547A IO expander (for possible use on the AdaPilot project).

I seem to have fritzed one or two of the pins on my STM32F429I-DISC0 board (now replaced by an updated version, STM32F429I-DISC1; that last character was a 0!); after some hair-pulling it turns out that one of said pins is used by the only externally-accessible I2C peripheral on the board; so, until the replacement arrives, here are some interesting facts about the PCF8547A.

Recovering an STM32F4 board

This is a note on overcoming a problem connecting to my STM32F429I-DISCO board.

Arduino Due and the Watchdog

A watchdog is used to detect when a system has gone off with the fairies; you have to reset the watchdog timer ("pat the watchdog") every so often or it takes some recovery action. In the case of the Arduino Due, with the ATSAM3X8E MCU, the recovery action is to reset the CPU.

In the ATSAM3X8E (and probably other Atmel MCUs, too), the watchdog timeout defaults to 16 seconds, and the default hardware state is that the watchdog is enabled! (the default in the Atmel Software Framework is to disable the watchdog unless you have defined CONF_BOARD_KEEP_WATCHDOG_AT_INIT).

Arduino Due/Segger J-Link EDU

I’ve been porting my Cortex-based RTS to Arduino Due, using the J-Link JTAG interface (because who can make an RTS without a debugger?). I’ve probably forgotten my initial problems with ST-LINK (an equivalent interface included for free on the STM32F4 board, supported by OSS software), but it seemed a much less trying experience than with Segger.

There are two things with J-Link GDB Server: first, it seems like a bad idea to keep the server alive after a GDB session ends, so start it with -singlerun; and second, you absolutely must issue monitor reset before running your program. If you don’t you’ll end up like I did, scratching my head for three days trying to understand why I was getting a HardFault at the SVC that FreeRTOS uses to kick tasking off.

Building a runtime system for arm-eabi

AdaCore provide a compiler (running on Windows and Linux) targeted to ARM (target arm-eabi) and a runtime system (RTS) supporting the Ravenscar profile.

The public version of the AdaCore Ravenscar RTS is released under the full GPL. It seemed as if it would be a good idea (and fun!) to produce an independent RTS with the GCC Runtime Library Exception (FAQ).

Building GCC 5.1.0 for arm-eabi

These notes describe building GCC 5.1.0 for the Cortex M4 on Mac OS X.

My target board is the STM32M4F29I Discovery.

Building GNAT GPL 2014 for arm-eabi

These notes describe building GNAT GPL 2014 for the Cortex M4 on Mac OS X.

My target board was the STM32M4F29I Discovery.