Hello

Welcome lekule blog

Hi, I`m Sostenes, Electrical Technician and PLC`S Programmer.
Everyday I`m exploring the world of Electrical to find better solution for Automation.
together in the world. #lekule86
Join us on

Teardown: Mini Network Router

Devices connecting to the internet are increasingly using wireless connections as opposed to a wired connection. Such a connection reduces clutter and cost while barely sacrificing on data transfer speeds. In this teardown, we will look inside a mini router that creates a wireless local area network.

Key Parts

  • Atheros SoC AR9331-AL3A
  • elixir N2DS512
  • Winbond 25Q128FVSG

The Casing

The router sits in a small moulded plastic container which has various IO ports and LED indicators. The sides of the router include a small vent, ethernet ports, USB power ports, and buttons. The top side of the case has three indicators which indicate power, user configuration, and wireless network enablement.


The wireless mini router


The vent on the side


Various IO and a second vent


Ethernet ports on the other side

The underside of the case includes all the product information including the unit's IP address, model number, SSID, default password, and MAC.


Underside showing information and more vents

The casing is made up of two parts: the top square container and a base that is held in using wedge-shaped clips. Opening the unit only requires a small flat head screwdriver and a bit of prying, popping the base off the unit.
The PCB inside the unit is not held in with screws or fittings but instead sits in plastic pieces that fit into holes on the PCB.


The view once the base comes off


The PCB removed

The PCB: Underside

The underside of the PCB reveals some interesting PCB production techniques as well as a mixture of surface-mount and through-hole parts.
The ethernet connectors show resistors and capacitors connecting to IO which are typically used to smooth edges on switching signals. Smoothing is needed because signals which have sharp edges produce harmonics which can interfere with nearby electronics. Such interference would break FCC and CE regulations, so a product must comply with those regulations to be eligible for sale.


Ethernet and passive components for smoothing

Near the USB A connector is an 8-pin IC surrounded by various passive components. This part, identified as AZ88 (or possibly AZ8B), does not have a datasheet that can be found online. However, considering that this unit is provided power over the USB connector, as well as the use of large capacitors and an inductor, it is fair to say that this could be a DC-DC converter that produces a 3.3V source from the 5V USB. Another tell-tale clue is the size of the traces connecting to the various pins.


"AZ88", most likely a DC-DC converter

Just below is a Winbond 25Q128FVSG which is a 3V 128M-Bit (16MB) serial flash memory IC in an SOIC package. This most likely contains boot information for the main controller as well as storing information such as SSID, network configuration, and other important parameters.


The 25Q128FVSG

Just below the memory IC is a portion of missing power/ground plane. This has been done because the opposite side of the board has a PCB antenna. The ground plane, which is fantastic at absorbing stray EM signals, would severely inhibit the device's ability to send and receive signals.


The missing plane for the Wi-Fi antenna

The underside also contains many resistors connected to traces as if they were series resistors in a bus of some kind. The other side of the PCB contains a few large ICs that are obviously to do with data processing and so it would make sense if these resistors are series resistors. Series resistors on fast-changing signal traces perform two functions:
  • limit current and help to prevent damage to parts
  • help to prevent reflections
While current limiting is unlikely, reflections can be a serious problem in high-speed circuitry. When a signal is sent down a PCB trace, impedance mismatches between the source and destination can result in electrical signals “bouncing” back and forth. This is an issue because it can confuse devices into thinking that there is a valid signal on the line. Series resistors not only help to match the impedances but also help to resist against these reflections.


Series resistors on a bus


Some more series resistors

The last two parts of interest on the underside are the 25 MHz crystal and some gold lines. These gold lines are connected to the floodplain and their function is not known. If you can shed light on this, let me know in the comments below.


Crystal and gold line

The PCB: Topside

The topside of the PCB contains through-hole and surface-mount components, as well as the main ICs that make the product.


The main PCB

The first IC of interest is the large Atheros SoC which is identified as an AR9331-AL3A. This SoC is specifically designed for use with 2.4GHz 802.11n communication and includes a MIPS 24K core, five ethernet switching ports, USB, I2S, UART, and GPIO. This processor uses JTAG debugging, which means that somewhere on this PCB we may find a debugging port or header that could allow this product to be reversed engineered.


Main processor, the Atheros AR9331-AL3A

Next to the SoC is the elixir N2DS51216DS, which is a 512Mb SDRAM high-speed CMOS memory IC. This IC would explain the large number of series resistors found underneath the PCB (these resistors would sit in the middle of the address and data lines).

The memory SDRAM IC, elixir N2DS51216DS

Next to the SoC is the Wi-Fi antenna on the PCB and, interestingly, the antenna trace also has an antenna port connected to it. This may have been put in during development for debugging reasons but why it's included on the PCB now (considering the lack of an external antenna) is beyond me.
Next to the antenna port (labeled as J13) is a fiducial used for pick-and-place machines, various surface-mount parts, and a surface-mount switch.


Antenna, ports, and components


More IO and components

Interestingly, the product contains a three-pin header which is clearly connected to a UART port (Rx and Tx give that away). The function of this is most likely to either bootload code into the main SoC and/or upload data into the serial flash.

Since it is unlikely that the company that produces this product gets memory pre-programed, they will program the devices themselves once the unit has been constructed. The pin header allows an employee to connect up a header and click “download” on the PC, which flashes the device.

The program header

Summary

This network router demonstrates not only how SoCs are taking over but also how PCB layout and design is still critical in modern products. Just because many parts are being integrated into a single package does not mean that key PCB techniques such as the use of ground planes, stitching vias, series resistors, and plenty of EMC control are unneeded. 

Share this:

ABOUTME

Hi all. This is deepak from Bthemez. We're providing content for Bold site and we’ve been in internet, social media and affiliate for too long time and its my profession. We are web designer & developer living India! What can I say, we are the best..

Post a Comment
My photo

Hi, I`m Sostenes, Electrical Technician and PLC`S Programmer.
Everyday I`m exploring the world of Electrical to find better solution for Automation. I believe everyday can become a Electrician with the right learning materials.
My goal with BLOG is to help you learn Electrical.

Labels

LEKULE TV EDITORIALS ARTICLES DC ROBOTICS DIGITAL SEMICONDUCTORS GENERATOR AC EXPERIMENTS MANUFACTURING-ENGINEERING REFERENCE FUNDAMENTAL OF ELECTRICITY ELECTRONICS ELECTRICAL ENGINEER MEASUREMENT TRANSDUCER & SENSOR VIDEO ARDUINO RENEWABLE ENERGY AUTOMOBILE TEARDOWN SYNCHRONOUS GENERATOR DIGITAL ELECTRONICS ELECTRICAL DISTRIBUTION CABLES AUTOMOTIVE MICROCONTROLLER SOLAR PROTECTION DIODE AND CIRCUITS BASIC ELECTRICAL ELECTRONICS MOTOR SWITCHES CIRCUIT BREAKERS CIRCUITS THEORY PANEL BUILDING ELECTRONICS DEVICES MIRACLES SWITCHGEAR ANALOG MOBILE DEVICES WEARABLES CAMERA TECHNOLOGY COMMUNICATION GENERATION BATTERIES FREE CIRCUITS INDUSTRIAL AUTOMATION SPECIAL MACHINES ELECTRICAL SAFETY ENERGY EFFIDIENCY-BUILDING DRONE CONTROL SYSTEM NUCLEAR ENERGY SMATRPHONE FILTER`S POWER BIOGAS BELT CONVEYOR MATERIAL HANDLING RELAY ELECTRICAL INSTRUMENTS ENERGY SOURCE PLC`S TRANSFORMER AC CIRCUITS CIRCUIT SCHEMATIC SYMBOLS DDISCRETE SEMICONDUCTOR CIRCUITS WIND POWER C.B DEVICES DC CIRCUITS DIODES AND RECTIFIERS FUSE SPECIAL TRANSFORMER THERMAL POWER PLANT CELL CHEMISTRY EARTHING SYSTEM ELECTRIC LAMP FUNDAMENTAL OF ELECTRICITY 2 BIPOLAR JUNCTION TRANSISTOR 555 TIMER CIRCUITS AUTOCAD BLUETOOTH C PROGRAMMING HOME AUTOMATION HYDRO POWER LOGIC GATES OPERATIONAL AMPLIFIER`S SOLID-STATE DEVICE THEORRY COMPUTER DEFECE & MILITARY FLUORESCENT LAMP INDUSTRIAL ROBOTICS ANDROID ELECTRICAL DRIVES GROUNDING SYSTEM CALCULUS REFERENCE DC METERING CIRCUITS DC NETWORK ANALYSIS ELECTRICAL SAFETY TIPS ELECTRICIAN SCHOOL ELECTRON TUBES FUNDAMENTAL OF ELECTRICITY 1 INDUCTION MACHINES INSULATIONS USB ALGEBRA REFERENCE HMI[Human Interface Machines] INDUCTION MOTOR KARNAUGH MAPPING USEUL EQUIATIONS AND CONVERSION FACTOR ANALOG INTEGRATED CIRCUITS BASIC CONCEPTS AND TEST EQUIPMENTS DIGITAL COMMUNICATION DIGITAL-ANALOG CONVERSION ELECTRICAL SOFTWARE GAS TURBINE ILLUMINATION OHM`S LAW POWER ELECTRONICS THYRISTOR BOOLEAN ALGEBRA DIGITAL INTEGRATED CIRCUITS FUNDAMENTAL OF ELECTRICITY 3 PHYSICS OF CONDUCTORS AND INSULATORS SPECIAL MOTOR STEAM POWER PLANTS TESTING TRANSMISION LINE C-BISCUIT CAPACITORS COMBINATION LOGIC FUNCTION COMPLEX NUMBERS CONTROL MOTION ELECTRICAL LAWS INVERTER LADDER DIAGRAM MULTIVIBRATORS RC AND L/R TIME CONSTANTS SCADA SERIES AND PARALLEL CIRCUITS USING THE SPICE CIRCUIT SIMULATION PROGRAM AMPLIFIERS AND ACTIVE DEVICES APPS & SOFTWARE BASIC CONCEPTS OF ELECTRICITY CONDUCTOR AND INSULATORS TABLES CONDUITS FITTING AND SUPPORTS ELECTRICAL INSTRUMENTATION SIGNALS ELECTRICAL TOOLS INDUCTORS LiDAR MAGNETISM AND ELECTROMAGNETISM PLYPHASE AC CIRCUITS RECLOSER SAFE LIVING WITH GAS AND LPG SAFETY CLOTHING STEPPER MOTOR SYNCHRONOUS MOTOR AC METRING CIRCUITS BECOME AN ELECTRICIAN BINARY ARITHMETIC BUSHING DIGITAL STORAGE MEMROY ELECTRICIAN JOBS HEAT ENGINES HOME THEATER INPECTIONS LIGHT SABER MOSFET NUMERATION SYSTEM POWER FACTORS REACTANCE AND IMPEDANCE INDUCTIVE RECTIFIER AND CONVERTERS RESONANCE SCIENTIFIC NOTATION AND METRIC PREFIXES SULFURIC ACID TROUBLESHOOTING TROUBLESHOOTING-THEORY & PRACTICE 12C BUS APPLE BATTERIES AND POWER SYSTEMS DC MOTOR DRIVES ELECTROMECHANICAL RELAYS ENERGY EFFICIENCY-LIGHT INDUSTRIAL SAFETY EQUIPMENTS MEGGER MXED-FREQUENCY AC SIGNALS PRINCIPLE OF DIGITAL COMPUTING QUESTIONS REACTANCE AND IMPEDANCE-CAPATIVE SEQUENTIAL CIRCUITS SERRIES-PARALLEL COMBINATION CIRCUITS SHIFT REGISTERS WIRELESS BUILDING SERVICES COMPRESSOR CRANES DIVIDER CIRCUIT AND KIRCHHOFF`S LAW ELECTRICAL DISTRIBUTION EQUIPMENTS 1 ELECTRICAL DISTRIBUTION EQUIPMENTS B ELECTRICAL TOOL KIT ELECTRICIAN JOB DESCRIPTION INDUSTRIAL DRIVES LAPTOP SCIENCE THERMOCOUPLE TRIGONOMENTRY REFERENCE UART oscilloscope BIOMASS CONTACTOR ELECTRIC ILLUMINATION ELECTRICAL SAFETY TRAINING ELECTROMECHANICAL FEATURED FILTER DESIGN HARDWARE JUNCTION FIELD-EFFECT TRANSISTORS NASA NUCLEAR POWER VALVE COLOR CODES ELECTRIC TRACTION FLEXIBLE ELECTRONICS FLUKE GEARMOTORS INTRODUCTION LASSER PID PUMP SEAL ELECTRICIAN CAREER ELECTRICITY SUPPLY AND DISTRIBUTION MUSIC NEUTRAL PERIODIC TABLES OF THE ELEMENTS POLYPHASE AC CIRCUITS PROJECTS REATORS SATELLITE STAR DELTA VIBRATION WATERPROOF