Make it low-power. Buying off-the-shelf parts to meet these criteria is still a challenge, but the latest crop of modules makes the job easier.
Modules let designers develop custom configurations with minimum moving the design of the critical aspects of the system to the module vendors. This includes the processor and memory subsystem and usually most, if not all, of the peripheral interface. A carrier board typically contains connectors and devices not found on the module, such as storage or higher-performance video.
In many cases, vendors deliver a range of modules for their own interface standard, like Rabbit Semiconductor’s RCM4300 RabbitCore (Fig. 1). It includes a flash memory slot for removable storage, 512 kbytes of SRAM, an additional 1 Mbyte of SRAM, and 2 Mbytes of flash. The 100BaseT Ethernet interface is on the module. Five serial ports and a 12-bit, eight-channel analogto- digital converter (ADC) are available via a carrier board in addition to GPIO.
Small modules aren’t limited to low-end micros. General Micro Systems’ GMS P70x packs the latest Intel 2.16-GHz Core 2 Duo into a 4- by 4-in. package (see “Tiny Carrier And SBC Keep Cool,” right).
Several module standards do exist. COM Express provides support for PCI Express and other high-speed serial interfaces (see “COM Express: A New Standard” at www.electronicdesign.com, ED Online 8780). The latest variation on the standard introduces the 84- by 55-mm Nano form factor.
Check out MEN Micro’s XM50 for a more rugged environment (see “Module Targets Rugged Spec,” right). It is completely encased, providing EMC protection and conductive cooling. In terms of formfactor size, it is similar to COM Express
Keeping it small doesn’t necessarily mean module/carrier combinations. Boston Engineering’s 2.5- by 2.5-in. FlexStack starts with a single-board computer (SBC) based on Analog Devices’ 32-bit Blackfin digital signal controller (Fig. 2). The dual connector bus provides a rugged stacking mechanism. The stack can run uCLinux. It also supports National Instruments’ LabVIEW. Even small packages like FlexStack can utilize high-end development tools.
For more mobile requirements and prototypes, try the BUGbase from BugLabs (see “Proto Heaven,” ED Online 18089). BUGbase has an ARM135JF-S-based microcontrol ler plus sockets for Bug modules, including peripherals such as LCDs and digital cameras.