NFC-based self-testing of embedded systems

Introduction

Electronics are everywhere now. Electronics-based systems usage has exploded exponentially and has entered all aspects of our life — automotive, white goods, entertainment, wearables and more.

This has happened due to the integration of electronic devices to make complex and computationally intensive microcontrollers and SOCs (systems on chip). Today, consumer whitegoods and electronic designs are getting complex day by day, which is bringing the focus of designers to ease of usage and troubleshooting.

The complexity of design requires greater need for internal debug information to understand what is happening inside the computing unit. If there are faults or failures seen, these can be retrieved and checked at various stages of product life cycle as shown below.

Figure 1: System check at various stages of product life cycle.

Product development and engineering

For embedded systems, it may be necessary to observe and certify the reliability of the product by checking the performance over a long period of time. Manually observing the behaviour of the system may not be feasible or efficient. It can be challenging as well to analyse big data and needs specific analysis.

Intermittent failures or conditional failures can only be debugged after the right logging of events and error cases. This information is already available and checks are already put in place by the developer. Providing this information externally for analysis requires a small amount of memory or dumping of the internal information.

Product manufacturing

These self-tests and error codes or messages are helpful in quality assurance during product development and manufacturing, optimisation of test time and production tests, and even post-sales maintenance.

If there is an error, the system already provides the information on which part was not able to communicate well and hence caused the problem. This can be tested or debugged by a technician easily and repairs can be carried out.

Logistics logging

Some key products may require a specific mode of transport and logistics. These kinds of systems may keep track of environmental and handling electronic data in the internal memory, like shock, humidity and temperature. These data can be analysed at destination to check if the product was moved and handled appropriately.

In-field service

The user can use a smartphone to retrieve the internal information of the product installed in the field. This information is very useful for maintenance service providers and can help the company to inform staff to be prepared for the service call. This not only reduces the number of visits for maintenance but also the length of the service call.

Currently used methods for debugging systems

While LEDs, LED segments and LCDs have limited capability to provide error information, smart connectivity can provide much more information to the user. This opens new way of capturing information, debugging, production level quality checks and optimisation of test time and post-sales maintenance.

New smart connectivity method for debugging using NFC

Most embedded systems have internal non-volatile memory for the storage of some system parameters. When this EEPROM is replaced by a Dual Interface EEPROM, it can further be used for error reading and system health using wireless communication.

Active RFID tags can provide cost-effective error code logging that can be retrieved by an NFC interface. NFC (near-field communication) is a wireless technology based on RFID (radio-frequency identification) at 13.56 MHz that establishes communication between the devices by bringing them in close proximity. Today, most mobile phones have an NFC interface. This can be used to communicate with active tags to the information exchange with the user.

System architecture

Consider that in a system, like a consumer product, an active tag can be very useful for self-diagnosis. When the system is powered ON, all parts of the system are checked and the status is written in the already available active tag. This can be read during the final quality check and if all the parameters are found to be okay, the product is shipped.

Testing all parts of the system in one step can also save time on the production line. It takes a few seconds of time to read the system health. A smartphone or reader can show the meaning of the error using suitable apps and the interface can be easy to use.

If there is an error, the system provides the information on which part was not able to communicate well and hence caused the problem. This can be tested or debugged by a technician easily and repairs can be carried out.

This method can also be used in post-sales support. The user can just touch the smartphone on the panel of the whitegood and read the internal information via NFC. This information can be sent to the central servers while logging the complaint automatically via WAN connectivity like Wi-Fi or GPRS connection.

Figure 2: Smart connectivity options for system health check.

Implementing NFC-based smart connectivity for easy debugging

A microcontroller-controlled embedded system can test its internal logic and external peripherals connected with it. Self-test reports can be updated on smartphones using NFC. Some testing commands can be given using a phone to further analyse the problem.

NFC connectivity is a cost-effective, compact and noise-free solution which can be incorporated easily even in small systems.

Today, mostly, people have smartphones which can be used to test systems and to provide preliminary information along with the type of fault, which can be displayed on the phone using Android applications. For better understanding, see the below example of a pedometer system.

Figure 3: Block diagram of wearable pedometer system.

A wearable pedometer is implemented using an STM32L series microcontroller, which reduces the power requirement for concerned applications and provides adequate processing capabilities suitable for this application. It also has various on-chip peripherals like SPI, I²C and ADC, which helped in designing a low-cost and low-power solution.

The dynamic NFC/RFID tag IC M24SR64-Y has the capability to operate from an I²C interface or via a 13.56 MHz RFID reader or an NFC phone. It helps in establishing low-cost RF communication between the pedometer and phone. It embeds an EEPROM memory which is used to save the system status and other required information.

Figure 4: Wearable pedometer and PCB.

To take the advantage of the troubleshooting system without opening it, an Android app has been developed which can communicate with the system without making physical contact. Even the dynamic NFC/RFID tag IC does not require a power supply to communicate using an RFID reader. To check the status of the system, a phone has to be brought near the system to initiate communication.

Figure 5: NFC-based troubleshooting system.

The dynamic NFC/RFID tag IC has a pin which can be configured to generate an interrupt for the main controller to wake up the system with the presence of NFC. With the interrupt, the system can run configured tasks to check the system health and write the status in an NFC IC. NFC can be read using an RF link to check system status. Eventually the phone displays the system status: ‘System OK’ pops up to say that overall system is okay, whereas ‘System Fault’ pops up in the case of faulty systems, mentioning the area in which the fault has occurred.

Figure 6: Phone display showing system status.

Conclusion

Smart connectivity in systems can provide multiple benefits starting from the production to the servicing in the hands of the customer. This can help reducing the overall cost of the product. Out of the smart connectivity options available today, NFC could be a good choice as it is economical and requires very low power and space, which makes it suitable for any application — whether small or big.

Top image credit: ©stock.adobe.com/au/vege

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