This paper presents a design approach f o r implementing a fault-tolerant embedded computing node based on the use of low-cost commodity microcontrollers. A combination of software and relatively simple external logic is used to implement fault-tolerance in a redundant set oj microcontrollers. A node can be protected with different amounts of redundancy (duplex, triplex, hybrid) depending upon the needs of its host subsystem, and is intended to be interconnected with other nodes into a modular distributed network. The structure of the node, and fault detection and recovery algorithms are described, along with a description of an experimental testbed that is being implemented.'

This paper presents a fault-tolerant design approach to allow

Microcontrollers provide very dense functionality for embedded applications ranging from telephones to automobiles. The acceptance of these devices for space applications has been hindered by their manufacture which often uses multiple semiconductor fabrication techniques and thereby compromises radiation tolerance.If such concerns could be mitigated, microcontrollers would provide a substantial increase in performance for builders of spacecraft electronics. This paper presents hardware considerations for using commercial microcontrollers in space applications. The motivations for starting with commercial devices and the concerns associated with their use are presented.The advantages of software versus hardware voting schemes to mitigate single-event effects are discussed. Interprocess communications approaches and schemes for improving I/O robustness are presented.

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