Heightening the Security of IoT Networks

Heightening the Security of IoT Networks

IoT is in danger of being a victim of its own success — the more pervasive it becomes, and the greater the number of nodes it comprises, the larger the attack surface it will present to potential hackers. Discover some of the advanced hardware and key strategic approaches that will help to keep IoT implementations secure in an increasingly hostile application landscape, while also adhering to exacting cost and power consumption constraints.

Design Products That Meet Their Intended Requirements

Practical steps in design verification using a DAQ data logger

Design verification plays a crucial role in the product development life cycle. Ensuring products are designed as intended is a rigorous and disciplined design process control.

Find out how to perform product characterisation using a data acquisition (DAQ) system to improve test efficiency and effectiveness. View the white paper to learn key practical steps to help you achieve your goals in design verification.

5-146281-2 – Pin Headers for Arduinos and Breadboards

Small companies usually lack the dedicated engineering facilities required for prototyping parts with extremely fine pitch – getting BGA soldered at home is tremendously difficult and almost impossible.

A nice way to get small companies interested in your product involves offering evaluation boards. These usually end up in a breadboard or a socket, where the pitch of 2.54 millimeters has established itself as a quasi-standard. This odd pitch, quite incidentially, dates back to imperial units – it is equal to 0.1 inch.

When designing such breakout boards, cost should not be the primary factor. Saving money on the headers is stupid – if they corrode, precision parts get problems. Due to that, using high-quality mechanicals from an established company such as TE Connectivity makes perfect sense.

The 5-146281-* family can be considered the standard offering for the 2.54mm standard. They are series of pins attached to one another, which can be broken down with scissors if smaller dimensions are needed.

Acquiring them is not particularly difficult. TE Connectivity offer them in a range from 1 to 40 pins in a single row, the individual part numbers can be taken from the table.

…the part number contains information about the number of pins found in the header

The parts at hand should not be limited to Arduino shields and similar interfaces. They can also be used to create test points where an advanced debugging peripheral can be attached. The scope ranges from in certain in-circuit debuggers such as Microchip’s ICD family to custom testing rigs used for product development.

Interestingly, pricing can be an issue. The two-pin variant starts out at like 50 cents, while the 40 pin variant sets you back like 3.6€ – if you have time on hand, breaking parts down in-house is a neat way to reduce costs.

TT Electronics ULW3-100RJA1 – A Resistor Which Doubles as a Fuse

In many cases, a resistor is found in series with a fuse. If an assembly is intended to be factory-maintained only, fusible resistors let you eliminate one of the components.

Fusible resistors usually come in device families. We will focus our attention on the ULW3-100RJA1 – it is a 100 Ohm through-hole resistor with a rated power of 3 watts. A variety of lead options are offered, as is shown in figure one.

…TT Electronics offer their fusible resistors in various lead configurations

Through-hole parts may increase assembly costs, but are beneficial for repair – if your technicians are instructed to cut the leads before desoldering the part, minimal amount of heat stress is to be expected inside of the PCB. Due to the high levels of heat reached during “shutdown”, PCBs should be of high quality – if the PCB catches fire, the fuse failed its function.

Fusible resistors, generally, are slower than dedicated fuses. In the case of our part, a five second overload of 15 watts is considered allowed – the circuit needs to be able to withstand significant overcurrent if a fusible is to be the only protective element used.

Finally, keep in mind that ambient temperature directly affects the switching voltage levels. Figure two, taken from the datasheet, shows that the rated power starts to fall at about 25 degrees celsius.

Ambient temperature has significant impact on current levels…

TT Electronics obeys the UL1412 standard, which can be considered the go-to set of rules for fusible resistors – visit https://standardscatalog.ul.com/standards/en/standard_1412_5 to find additional information not found in the datasheet.

LM2653MTC-ADJ from Texas Instruments

Texas Instruments offers engineers a set of switching regulator evergreens which combine high efficiency with simple PCB layouts. The highly efficient LM2653, first introduced in 1999, usually stands in the shadow of his SimpleSwitch-branded brothers.

While the letter are expensive and don’t deliver high efficiency, the LM2653 performs efficiently and affordably over a wide range of output currents.

…the part at hand is efficient at both low and high currents.

From a technical point of view, there is not much to say about the part. It is a switching regulator which boasts a working frequency of 300kHz, and uses a coil and an inductor to perform a bucking operation. An example schematic presents itself like figure two.

…setting up the advanced features requires a set of capacitors and resistors

The relative complexity of the example can be explained by looking at the block diagram. In addition to the thermal and overcurrent protection available in almost all switching regulators, the part contains a set of delay circuits which perform additional safety checks.

Hot feature number one is the soft start capacitor, which usually gets connected to pin SS. The IC charges it with the current of about 2 µA, and watches the voltage level until it reaches 2V. That way, the system starts up slowly, which can be helpful when charging capacitors and other elements.

Secondarily, the system has undervoltage and overvoltage protection. Should the load be able to sink the voltage to less than 80% of the desired value, a delay capacitor is charged slowly but surely – when it reaches a voltage level of 2V, the part switches off the supply to prevent short circuit and similar damages.

From a technical point of view, the part at hand is relatively docile. The datasheet contains detailed information on capacitor and diode selection, and comes with a few precalculated examples. The IC itself is available in TSSOP housing with sixteen pins.

M24xxx Series – Cheap Memory for Microcontrollers

Cheap memory for microcontrollers

No matter how large your microcontroller’s memory might be – in practice, you will always need just a little bit more. In that case, STMicroelectronics’s SPI EEPROM provides a nice alternative to more established players.

Obviously, the biggest advantage of SPI involves the simplicity in connecting the part – you don’t need to worry about limited I2C address ranges or other problems. If your application has a free SPI controller, you are ready to go.

…if multiple CS pins are available, adding SPI EEPROMs becomes really simple

Alternatively, an SPI MUX can be driven from the GPIO port bank in a fashion similar to the bank switching implemented in Solomon Systech’s display controllers. Either way, the maximum permitted clock frequency is set at relatively speedy 5MhZ. STM simplifies the design of such boxes by providing a dedicated hold output input. If hold is activated, the serial data output line becomes high independence, while inputs and clock inputs are discarded silently.

A question of complications

ST‘s part differs from its colleagues in that it’s memory is organized in a set of banks. The total amount of spacious 2Mbit is divided into a groups of pages made up of 256 bytes each, one of which can be designated as a read only identification page intended to store serial numbers and similar information.

Actually interacting with the SPI flash then is accomplished via a set of dedicated instructions shown in the figure.

Eight bit instructions set the operational mode of the chip

Finally, keep in mind that ST also goes after the extremely lucrative I2C EEPROM market. Their offering for this market is called M24xxx. Both chip families are automotive certified, thereby permitting their usage in challenging environments.

BlueNRG-1 bluetooth without hassle

Designing and impendance matching RF-related circuitry is an art of its own. STMicroelectronics’s SPBTLE-1S combines a Bluetooth 4.2 radio module with a Cortex-M0 processor intended to handle RF communications.

A look at the block diagram confirms that the module is, by and large, an SoC in a box. Thanks to STM pre-soldering it all onto a planar, certification hassles are avoided (in the USA) or mitigated (in Europe).

The SPBTLE-1S contains all an IoT developer dreams of at night…

Interaction with external hardware can be accomplished via a full complement of GPIO ports, two ADC channels, one SPI and two I2C interfaces. The module, furthermore, has the capability to work as a dedicated Bluetooth 4.2 radio chip being controlled by a seperate microcontroller.

ST Microelectronics prides itself on the module being able to run from a single coin cell or a pair of AAA batteries – any input power ranging from 1-.7V to 3.6V is acceptable. This, sadly, is a problem for hosted mode – interfacing the module with a run of the mill 5V microcontroller requires level switching hardware. Power consumption in active mode is 1.9mA, with a 0.9 Microampere sleep mode also available.

Integrating the module is relatively simple: STMicroelectronics picked a form factor similar to the one used by the various ESP32 modules. This means that even non-sophisticated pick and place houses should not have trouble handling the part – if land geometry is suitable, hand soldering also is possible due to the pads being exposed from both sides.

…the SPBTLE-1S can be soldered by hand

Unlike some other products from STM, the SPBTLE-1S does not stand alone. It, instead, can use almost all example code provided for the BlueNRG platform – getting started with it is as easy as selecting a C program’s skeleton which fits your needs.

Texas Instruments’ OPA333 & OPA2333

TI’s micro-power OPAx333 opamp goes where few opamps have gone before

No matter how advanced your digital circuitry is: sometimes, you need an OpAmp. Technology improvements allow for low-power rail to rail OpAmps such as the OPA333.

Running operational amplifiers from a single supply is a sure-fire way to cause problems while training. Generating positive and negative supply voltages gets tedious when working on a low-power design. Having to make do with supply voltages as low at 1.8 V complicates things further.

TI addresses that problem with the low-power operational amplifier at hand. The chip works with supply voltages as low as 1.8 V. Should you feel like splitting them, the limits become -0.9 V and 0.9 V. The largest allowed supply is a generous 5.5 V – a value well known to microcontroller circuit designers. Another interesting aspect is the advanced rail to rail capability: the output voltage can approach the supply voltages to a margin of 50mV. This makes the part ideally suited to sensor information conditioning.

Texas Instruments intends the part for precision applications. In addition to the low CMRR, the part has a temperature drift in the range of but 0.05uV/°C. Its quiescent current is around 17yA – compare this to older parts to find out that our new contender is much more efficient.

Treasure trove of knowledge!

Texas Instruments data sheet team outdid itself when describing the OPA333. The datasheet…

…doesn’t limit itself to the specifications. It provides valuable insight into circuit design and PCB layout for low power OpAmps. This makes the document valuable even if you work with other operational amplifiers. From a packaging point of view, Texas Instruments is flexible. The parts are available in SOT23, SOT and SOIC housings, the latter of which can be soldered by hand.

Should you need two operational amplifiers of the type, switch to the OPA2333. It combines two of the parts in a fashion similar to the one shown in the figure.

…the OPA2333 combines two low power OpAmps in one

It, furthermore, is somewhat price competitive – the two figures show you OEMSecrets best prices as of the writing of this story.

Nordic Semiconductor’s nRF52840

Nordic Semiconductor evaluation kits for cheap

Nordic semiconductor is the king of the wireless hill. Their chips support a variety of protocols used in the internet of things.

The recently announced nRF52840 Dongle uses the nRF52840 chip on a USB stick-like PCB. The $10 planar can plug into a PC. After that, it supports all Nordic semiconductor development tools.

…the PCB doubles as USB connector.

Keep in mind that debugging is not available on these evaluation boards. If you want to debug, a more expensive development kit such as the nRF52840 DK is needed. Due to the high price, distributor margins are wide. Take a look at the figure to see how OEMsecrets can save you money.

Prices fluctuate violently when emulation kits get expensive…

From technical point of view, the dongle is extremely versatile. It supports Bluetooth 5, but can also be used with other protocols:

• Bluetooth LE
• Bluetooth Mesh
• Thread
• Zigbee
• 802.15.4

In addition to these features, the product also has a set of GPIO pins available from the side of the PCB. The interface pinout is somewhat difficult to find, but is available for you right here.

Thanks to the presence of the supply pins, the PCB can be used in a standalone fashion. Program it from your PC, and solder it to your circuit to get started. Due to a price of less than 10 USD a pop, small series could even use the PCB like a process computer.

Nordic’s nRF-Dongle also provides distributors with a nice margin…

Laird DA1206C121R-10 Ferrite bead networks

Ferrite bead networks – it takes multiple beads to tango

Ferrite beads come in groups – if your circuit needs one, it usually doesn‘t take long until a regulator makes you add another. Laird now provides a resistor array-like solution for the ferrite bead problem.

For those of you new to the concept: a ferrite bean is a resistor which rejects high frequencies. Look at the impendance chart shown, which we took from the data sheet.

…the resistance of a ferrite bead increases with frequency

It takes but one look at to understand what a ferrite bead is good for: place it in series with a component to eliminate high-frequency radiation. Popular candidates would be switching regulators, but also a variety of other chips such as amplifiers which work by modulating carriers.

Laird’s part differs from the competition in that it combines four ferrite beads in a 1206 housing. This makes the part ideally suited for controlling outputs. Put it next to a chip which needs to be disciplined, and don’t worry about pick and place costs.

From a technical point of view, the part is a classic ferrite bead. Its maximum current current is 300 mA continuous, its resistance in the DC range is around 0.2 ohms.
The main issue is that its impendance starts to raise in the range of more than 10 MHz. This makes the part poorly suited to small amplifiers, whose carrier wave is in the range of 100 kHz or so.

Other than that, the part is a total buy. The figure shows the pricing, which is very much in line with four single ferrite beads. Furthermore, using dedicated ferrite beads requires more space on the PCB.

Keep repairability in mind when using this part. While the component is on the market since 2004, one never knows when it might be discontinued. Furthermore, if your equipment is used in areas with limited parts availability, saving maintainers the hassle of finding a ferrite bead array might be appreciated.