Electronic Design

Playing Games With the STM32

STMicroelectronics move into the ARM-based Cortex arena started with the STM32. The STM32 Primer (Fig. 1) was a way to get people started with basic software development. It was put together by Raisonance that has a range of products including development kits for a range of STMicroelectronics’ platforms.

This ARM 32-bit Cortex-M3 runs at 72 MHz, delivering 90 DMips of performance. It as 128 Kbytes of flash program memory and 20 Kbytes of SRAM. It can run off an embedded oscillator although this one also has a quartz crystal as well. Some of the 80 I/O pins are used internally but none are available without cracking the case. There are also onboard ADC and DAC interfaces plus USB 2.0, CAN, USART, SPI, I2C, and LIN.

The USB-based STM32 Primer plugs into a Windows PC where you can install the Raisonance's RIDE software toolset. The debugger is limited to 32 Kbytes of code, but the GNU C/C++ compiler is not limited. You can also utilize the Raisonance C compiler and Cosmic C compiler that provide better optimization but these have code size limitations. The package comes with a small CD that includes the tools and plenty of demo projects. More are available on STMicroelectronics’ Web site.

One thing that makes the STM32 Primer stand out is its use of MEMS-based 3D accelerometer tilt control. These are already linked to the STM32 microcontroller since this is more of a plug and play package than a hardware development kit. In fact, the LCD display and one button are the only interfaces with the exception of a USB interface to the chip. A second USB interface is used for debugging. There is a rechargeable battery within the unit and it can run off and recharge via the USB interface.

Installing the Raisonance Ride7 (Raisonance Integrated Development Environment) toolset was uneventful. The ICE works with the CircleOS installed on the STM32 Primer. The OS handles application management, menu interface, scheduling, LCD graphic functions, interfacing the MEMs sensor, as well as access to the LED, buzzer, and push button.

You can actually download multiple applications to the unit. Restoring the system to its initial state is relatively simply since it only takes the download of a single file from the installation CD.

The application approach is designed to allow sharing of CircleOS applications. There is even a Circle community on STmicroelectronics Web site.

This approach to an evaluation platform has a number of advantages. It is stable and development was fast because of the functionality provided by the CircleOS. It is not intended as a hardware development platform but that will not prevent some from cracking the case to get access to the I/O pins.

Overall, the STM32 Primer is a great way to get started programming the Cortex-M3.



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