Electronic Design

STmicroelectronics STR9-comStick

STmicroelectronics' (ST) STR9-comStick is a USB-based development and evaluation tool based on ST's STR912FW44 microcontroller. The MCU contains a 96MHz AMR9E ARM966E-S core. It has a range of peripherals include Ethernet, USB, CAN, and AC motor control support making it a heavy duty embedded platform. It is available from ST and Hitex Development Tools, supplier of much of the software in the bundled system. STR912FW44 Overview The microcontroller has a Harvard RICS architecture with a 5-stage pipeline. The instruction set includes single cycle DSP instructions. The chip family supports up to 512Kbytes of flash with an additional 32Kbyte bank. These are tightly coupled to provide single cycle instruction access in sequential burst mode. The memory is rated for 20 year retention and a minimum of 100K erase cycles. The SRAM limit is 96Kbytes. It can be backed up via battery power. The DMA support handles the Ethernet interface and up to 8 additional channels. The vectored interrupt controller supports 32 interrupts. The real-time clock provides calendar and wake-up functions. It also provides tamper detection support. A brown-out monitor is included. Peripherals on the shared 5V 80 GPIO pins include an 8-channel, 10-bit ADC with a 0 to 3.6V range and 0.7 usec conversion rate plus a 3-Phase induction motor controller (IMC) with 3 pairs of PWM outputs with adjustable centers, emergency stop support, dead-time gen, and tach input. There are also four 16-bit timers with PWM support. Communication peripherals include a 10/100 Ethernet MAC with an MII port, a USB Full-speed (12 Mbit/s) slave device, a CAN 2.0B Active interface, three 16550-style UARTs with IrDA protocol support, a pair of Fast I2C interfaces, a pair of SPI interfaces, and an 8/16-bit EMI bus. The chip has a JTAG interface with boundary scan and support for the ARM EmbeddedICE RT for debugging, It also has embedded trace module (ARM ETM9) support. The chip is available in a 12mm by 12mm LQFP80 or 14mm by 14mm LQFP128 package. The STR9-comStick The STR9-comStick keeps the chip under wraps; plastic that is. The board extends past the plastic casing to expose the Ethernet, USB slave interface and a 12-pin interface header. The latter provides access to the CAN interface and 8 GPIO pins. The latter include PWM output support. The remainder of the microcontroller's IO is inaccessible. The CAN interface is driven by an SN65HVD230 transceiver allowing direct connection to a CAN bus. The STR9-comStick takes power from the host USB interface. The 12-pin interface header can deliver 3.6V but don't try to drive lots of peripheral hardware from it. The documentation recommends that you install the software before plugging the stick into a Windows PC. There are a pair of LEDs inside the plastic covered region that are under processor contol as well. Software Installation The system comes with a pair of CDs, no printed documentation. One is Flash-based and provides a company and product overview but the bulk of the tech specs are on the second installation CD. The latter is a rather nice web-based solution. The only caveat is that is has some javascript that links to webtrendslive.com, a tracking site. My Firefox NoScript caught it since I am not fond of tracking software but it probably gives ST a better feel for when people are using the CD, not necessarily the product. The installation CD has full documentation on the stick, the chips, and the software. The documentation is extensive and very well written. The "Insiders Guide" is a fully linked PDF file. The software includes a range of packages include the Hitex tool chain with its HiTOP5 IDE for programming and debugging. It has a 16Kbyte code size limit but it is otherwise fully functional. There is also a GNU C/C++ compiler with no code size limit. There is an additional IDE called Development Assistant for C (DA-C) from RistanCase. It provides a C development environment with neat features like data flow graphs, flow charts and software metrics. It also has a nice documentation generator. The GNU tools can be used with Eclipse but you will need to download and configure the system yourself. There is plenty of C source code that works with all three platforms including an embedded web server, USB mouse emulator, and a CAN monitor. The "Insiders Guide" was written by HiTex so obviously the tutorials are tailored for their tools. Also, the guide is not specific to the STR9-comStick. Still, the overview is excellent and the architecture details are applicable to any development tool used with the stick. Getting the system up and running was a relatively painless exercise. It took longer to read the manual to figure out what software platform to use first. Go with the Hitex software first. Overall, the STR9-comStick is an excellent platform to get started with USB or Ethernet application development. It would have been nice if more peripheral interfaces where available. Likewise, it would have been handy if the system could run standalone. That may work if you provide power via the host USB interface but I don't know if the ARM9 is enabled by default if the unit is not connected to a USB host like the PC. If your primary target is a USB device, CAN or Ethernet platform or a combination there of then the STR9-comStick is the platform you want. You can be up-and-running in an afternoon. The PWM support is extensive on the chip but the limited IO exposure will make other alternatives more desirable if non-network device support is a priority. Related Links Eclipse HiTex RistanCase STMicroelectronics

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