Thought Leadership

May 13, 2015
Bite-sized Storage Solutions for Industrial IoT Applications
As IoT applications grow at a rapid pace, organizations must address the need for reliable data storage

By: Danny Lin, vice president of ATP and board member of the SD Association, and Saurabh Pande, business development and application engineering at ATP

The Internet of Things (IoT) is taking over the world. According to a McKinsey Global Institute report, the impact of the IoT on the global economy could reach $6.2 trillion by 2025. The same report estimates that the market for connected devices will grow to 20 billion or 30 billion units by 2020.

The use of IoT devices has grown exponentially in the past several years, to the point where they have become a part of daily life. There are three main categories of IoT systems: consumer, machine-to-machine and industrial machine-to-machine. Industrial applications include medical centers, security and surveillance demands, railways, air transportation, environment condition monitoring, disaster management and retail.

Given the impact that industrial IoT applications have on many different sectors, failure can prove catastrophic on several levels. Furthermore, this category of IoT applications is much more demanding than either consumer IoT or traditional machine to machine IoT. The communications requirements for these systems are not merely client/server. Rather, nodes act as peers on the network, each making decisions and reporting status to the other nodes.

Communication breakdown between the nodes is not an option. These systems often process tasks at greater rates than human beings can, so they must run reliably and safely, without human intervention. If data goes missing due to even a few minutes of downtime, it can result in the loss of vital information. In this way, communication failures can bring about added costs or even safety threats.

Compounding the high stakes, high demand aspects of industrial IoT applications is the nature of the devices. They are often quite compact. Storing data in a secure and accessible manner in a restricted space poses a major challenge.

The Perfect Fit

Fortunately, SD memory cards – a removable digital storage device – possess a number of characteristics that make them highly suitable for the demands of these devices.

  • SD memory cards are small, making them one of few solutions small enough for IoT devices. They are available in full size and microSD, so users have options.
  • They are reliable, solid in performance and power efficient. These characteristics are particularly beneficial for applications located in a remote or inaccessible area.
  • The cards offer flexibility, with a wide operating temperature range.
  • Users can implement reliability enhancing and error mitigation algorithms on the cards.
  • SD memory cards have become established storage solutions, and their capabilities have continued to grow due to technology advances.

Like any solution, SD memory cards do experience certain issues that can hinder their performance. However, users can overcome these hurdles.

Addressing Technology Challenges

IoT devices often operate without a break, and their sensors must record every single second of data. Any small delay of time in sending data from the SD memory card to its associated device can cause data corruption. If this happens, the device misses critical information it needs in order to function properly because the delay has interrupted data flow. Data in transit is lost, and as a result, the system attempts to function without implementing the most current information. This can lead to serious consequences.

The simple solution to this problem is to back up the data. Devices should include a backup battery, but a more streamlined option exists for SD memory cards. Manufacturers can program a backup code into cards that allows them to revert to a previous state; much like a PC or MAC can in the wake of a system crash.

Read/program disturb, an internal issue within the card architecture, presents a different type of challenge. This phenomenon occurs specifically in devices such as SD memory cards that use NAND flash. This issue arises when a charge leaks across adjacent cells located in a row within architecture that contains written data. There are no safeguards in place to prevent a charge from leaking from the target cell to its neighboring cell. If the neighboring cell already has a charge, the leak can cause what is known as a disturb. Disturbs are problematic because they reduce the life of SD memory cards.

Several watchdog solutions can help ward off disturbs. First, certain algorithms inside of the card act as a controller, checking cells at periodic intervals to ensure they are in the same state as they were previously. Second, if an unintentional change has occurred, auto refresh corrects errors to ensure charges are hitting target cells and data is correct. In order to take advantage of these features, it is imperative to purchase SD memory cards from a vendor that integrates this technology into the design.

Staying Cool Under Pressure

SD memory cards sometimes operate under extreme conditions when providing data storage for industrial IoT applications. The range of conditions includes temperature, humidity, pressure, mechanical vibrations or shock, radiation and high altitude.

Smart cars are a perfect example of an IoT application subject to one of the main conditions, temperature extremes. Theoretically, as their popularity grows, they will become more common in many different geographic locations, from bitter cold northern Russia to boiling hot Arabia. When constantly exposed to drastic temperatures, data loss makes the aforementioned smart car prone to various types of equipment failure.

This threat exists because temperature affects FLASH memory and data retention in the cards. Extreme conditions cause fluctuations in their ability to hold a charge, which in turn can harm their ability to retain data.

Sometimes the consequences are application specific. The navigation capabilities of a GPS system that stores maps via an SD memory card may suffer from extreme conditions. As a result, someone vacationing in California may discover that their maps application is useless for that trip.

SD memory card manufacturers can solve this problem with cards they test for durability under extreme temperature conditions. Emerging technologies have allowed vendors to produce robust cards that can withstand challenging external conditions. Users seeking storage solutions for industrial IoT applications should steer clear of cards manufactured for consumer electronics, as vendors in this sector do not typically account for extreme conditions when they design products.

Choosing an SD memory card for industrial IoT applications is a task that varies according to purpose. It depends largely on the application itself, as well as its operating environment. However, the golden rule for any application is to select an established manufacturer that designs products with the stability to endure for many years.

Danny Lin is the vice president of ATP and board member of the SD Association. At ATP, Danny is responsible for global supply strategic partnerships and alliances. With the SDA board of directors Danny is driving the continuous expansion of the SD memory card adoption in the non-traditional markets including IoT, Industrial/Embedded, Healthcare and Automotive. Danny can be reached at DannyL@us.atpinc.com.

Saurabh Pande is responsible for business development, solution engineering and technical marketing across ATP's existing and new strategic client base. Saurabh can be reached at SaurabhP@us.atpinc.com.

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