What is EDP?

Embedded design projects typically aim to have a proof-of-concept ready early in the project lifecycle. This requires some basic hardware, which is usually obtained by purchasing an evaluation board from the processor vendor or from a third party developer. However, hardware modifications may be required, and the project must usually absorb the full purchase price. Such kits are rarely re-usable in subsequent projects, either because the right features are not provided or the technology may have been superseded. A more cost-effective approach is to work using a modular development platform that can also be reconfigured throughout the longer term to meet requirements for initial hardware in future projects. The EDP fulfils this concept. It provides a baseboard into which are plugged processor modules and special-function modules as required by each project. This provides a trusted platform, suitable for long-term use, which will not only save purchasing numerous development kits but will also save the time to make any adaptations.

EDP EXPLAINED

Configurable Baseboard

The EDP baseboard, or motherboard, is an Extended Eurocard size (220 x 100mm) board that provides four identical “stations” for the plug in modules. The motherboard allows microcontrollers and I/O devices to communicate through a standardised interface similar to PC/104 or STE buses. However, whereas PC/104 and STE tend to support only power-line, data, address and control signals, the EDP interface supports microcontroller applications by also catering for specialist pin functions relevant to typical 8, 16 and 32-bit microcontrollers. There are three I2C channels, two CAN channels, an SPI port, and various signal measurement and signal-generation peripherals. There are also groups of pins to support interrupts in response to external events, groups of pins able to create pulsetrains, others dedicated to motor control, I2S, memory cards and many other common microcontroller IO types. Advanced interfaces such as SD/MMC are also supported. All of these signals are contained within two 0.8mm dual-row connectors of 140 and 100 pins each, called EDPCON1 and EDPCON2 respectively. The EDP motherboard also solves issues such as inter-module and inter-EDP system communications, using available interconnects such as I2C and CAN.

Plug-in Command Modules

This architecture allows a wide variety of processor modules, based on various microcontrollers, to be built by mapping the device I/O pins onto the EDPCON1 and EDPCON2 connectors. The microcontroller then appears to be a virtual CPU to another I/O device fitted on the bus, such as a digital or analogue peripheral module. It is possible to map almost any microcontroller to this format. The first Command Modules to be introduced for EDP have supported the Infineon XC167, STMicroelectronics STR9, and the Microchip Plug-in Module for microcontrollers and dsPIC devices (PIC-PIM) spanning 8-bit, 16-bit and 32-bit families.

Plug-in Functional Modules

Of course, since the EDP is conceived to provide a configurable platform for proof-of-concept work, its success is also dependent on providing a diverse range of peripheral functions that are also in EDPCON-compatible modules. The first modules to be developed as part of the EDP programme include analogue and digital I/O modules, a communications module, and two motor-control modules.

The EDP modular concept lends itself to the development of an increasing range of application modules going forward. RS is actively pursuing development of new modules; recent announcements include a new SD Card module and plans for modules to enable EDP-based wireless development. Users can also build their own modules, if required, by referring to the EDPCON bus specification.

A key challenge facing embedded systems developers is to build drivers for each of the functions to be implemented. The time taken to write and debug a driver, at the proof-of-concept stage, can delay the project; particularly if the driver will not work. Later in the project, it may be necessary to develop certain drivers further to achieve the full functionality and robustness. EDP solves both of these challenges by including all necessary drivers for each function. Moreover, the drivers are written from the outset to be production ready. Hence, developers can progress their projects without debugging drivers at the initial hardware stage or refining the drivers for production later in the project.