Even though an increasing number of applications are networked by wired or wireless methods, many system designers are consciously deciding that in new applications, data transport will be done through non-networked means. When networking is not possible or practical, engineers must face the challenge of transferring data to and from products through portable data carriers — a physical device containing non-volatile memory used for data storage and transfer. The type of data transferred includes firmware updates, feature enhancements, calibration data, configuration or recipe data, data logs, and usage monitoring and limiting. For example, a controller console in the field might need to have calibration and usage data uploaded from a disposable mating sensor.

There are a number of options for portable data carriers so engineers must be careful that the product they choose is best suited to the application. Commonly, consumer-based options such as smart cards, USB flash drives, and camera cards are not rugged enough for OEM applications. What's more, they come with many hidden costs.

The decision to go non-networked

Applications that require data transfers must trade off the cost of implementing, securing, and supporting a network infrastructure versus the hardware cost of a physical data-transfer mechanism such as a portable data carrier. When implementing a network, it costs little to scale up the number of installed nodes, especially in wireless networks. However, other subtle but substantial costs should be quantified before making the decision to rely on a network system for data transfer. For example, programming the infrastructure and its human interface can be a large, expensive engineering project with on-going software support costs.

Choosing a network places costs on the OEM's customer, thereby giving the product a downside. End-users will have to purchase infrastructure software and have IT personnel maintain network “up-time.” The recurring costs, such as operating system upgrades and security software subscriptions, must also be factored in. End-users will also be concerned with the security risks of providing a connection to their IT system.

Quantifying costs becomes easier when transferring data by physical data carrier devices. For instance, there is an up-front fixed cost per unit that accounts for the hardware of the data carrier and it's mating connector. After putting firmware in place, there is no need for ongoing engineering support of the data carrier solution. Further, because the OEM system accepts data carriers, it can be designed with a bootloader that will accept firmware updates from the portable data carrier if needed. This also requires that the data carrier have a stable configuration and availability throughout the production and support life of the OEM's product. The portable data-carrier system does not carry additional hidden costs to the end-user, making it easy to evaluate costs.

Memory considerations

There are a variety of data carriers with non-volatile read-write memory ICs. EEPROMs, Serial Flash ICs, and NAND-Flash products are the most common. A few considerations for selecting the optimal memory include the microcontroller's built-in interface, the needed memory capacity, transfer rate (clock speed) required, and what the designer prefers.

Embedded microprocessor applications often require far less memory than PC applications, making consumer products overkill and more expensive than the traditional options available to embedded systems engineers. However, there are a growing number of portable data applications that use large data files. There are now data carriers available that offer additional benefits to the embedded engineer even in these higher capacity applications. These new devices present the memory through a compact set of commands, freeing the embedded engineer from having to do all of the low-level programming associated with certain consumer devices. A few of these OEM-based products can also guarantee long-term availability, which is not guaranteed by devices targeted at ever-changing consumer needs.

Environmental hazards

It's essential to analyze the physical and environmental requirements in which the data carrier will be used. Review features such as physical size, data-carrier retention, durability, ESD performance, convenience, and other preferences. How often the data carrier will be used and under what conditions are also important factors that will influence the ideal package and memory selection. In many cases, a data carrier costs much less than 1% of the overall OEM's product cost, but it has a pivotal role in its operation, especially when downtime can be painfully expensive.

Data carriers used in light-wear consumer applications can use less durable materials, contacts, and connectors than in devices frequently inserted and removed from a system, or which must survive in hostile environments. OEM applications often require high-cycle life, reliable repeated use, and survival in harsh environments. Data carriers used in extremely harsh environments such as military and industrial applications may require even more heavy-duty materials and contact mechanisms.

Manufacturers of typical consumer memory devices do not provide receptacles nor do they guarantee performance of a mated data carrier and receptacle system. It is the designer's job to consider these details as well. Some OEM-based data carrier systems do address the receptacle as well and eliminate the need for the design engineer to modify a mating receptacle to meet specific environmental requirements.

Product lifecycle

Evaluate all life-cycle factors up-front. Post-release engineering support is often not considered in cost evaluations, but can have devastating effects on the financial success of a product. In evaluating the most cost-effective solution, overall system and support costs are often more important than the cost of the data carrier alone.

Most OEM products have lifecycles measured in years, not months. That makes long-term availability particularly important for portable data carriers in non-networked environments. Since the OEM product isn't networked, the portable data carrier becomes the only practical way of getting information into or out of the device. If the portable data carrier becomes obsolete or it's electrical or programming interface changes, this could force the OEM to embark on a costly requalification or redesign process.

For medical devices particularly, selecting data carriers with proven long-term support is a must. The design and approval process can take years, and after securing approval, it is desirable to make no changes in the medical device's components for the entire production life of the product.

Still, anticipate what the system might need in the future. For example, it could benefit from larger memory capacities, faster transfer rates, memory-management features, and a way to add features such as firmware updates. A data carrier that is part of a “family” has the highest probability of seamlessly addressing yet-to-be-anticipated future requirements.