Selecting the right network connection for your MCU-based machine-to-machine application - Embedded.com

Selecting the right network connection for your MCU-based machine-to-machine application

Based on its ease of use, low cost, high bandwidth, stability,security, and compatibility across devices, Ethernet has become the defacto standard of network access for 32-, 16- and even 8-bitmicrocontrollers, surpassing that of both SOHO and enterprise networksand expanding into the consumer electronics market.

The proliferation of M2M communications anticipates a rise inEthernet-capable microcontroller market. The question is, which is thebest way for you to add this connectivity?

Eight Embedded Ethernet Solutions
There are eight distinct configurations to embed Ethernet based on theinput/output interface (Figure 1 below ).The designer chooses the appropriate configuration based on theinterface needs of the target application.

The first three scenarios feature a microcontroller with anintegrated network controller; of these, the first scenario featuresthe highest degree of integration. The remaining scenarios (fourthrough eight) do not feature an integrated Ethernet controller, andare able to interface with an external network controller through aserial (i.e. USB host) or parallel (i.e. PCI or non-PCI local bus)interface.

Figure1. Which Embedded Ethernet Solution is Right for Your Design?

The first configuration in Figure 1 was once only possible with 16-bit and 32-bit microcontrollers, but thetechnological advances of the 8-bit microcontroller has allowed it tocapture more of the market with smaller form factors and higherintegration. Applications that once required a 32-bit microcontrollercan now be powered by the lower cost, highly integrated and highercapacity of 8-bit network microcontrollers.

The second scenario is divided into 8-bit, 16-bit, and 32-bitmicrocontrollers; the third scenario is dominated mainly by 16-bit and32-bit microcontrollers. The fourth and fifth scenarios, which use aPCI Bus, and the eighth scenario, which uses a USB host are serviced byhigh end 32-bit microcontroller, while the sixth and seventh scenarios,which use a Non-PCI bus, are able to be controlled through 8-bit,16-bit, and 32-bit microcontrollers.

The following elaborates on the three types of solution depicted in Figure 1 : The Non-PCI solution, theUSB solution, and the more powerful Single-chip solution.

Networking with a Non-PCIMicrocontroller
The configuration in Figure 2 below targets embedded systems without a PCI-bus but featuring a non-PCI orSRAM-like interface. This design can embed a MAC and PHY layer in theEthernet controller to provide network access, such as the eighthscenario in Figure 1 . Sincethe majority of microcontrollers provide the non-PCI local bus, thiscan provide a single-port network capability.

Figure2. Monitor, Control or Access Your Device over the Internet UsingNon-PCI Ethernet Controller

This solution is suitable for home appliances, industrial and homeautomation, security systems, remote management, streaming media, andhigh bandwidth networking. Figure 3below depicts some of these applications: POS (point of sale)devices, wireless access points, broadband routers, IP phones, mediasharing hosts, IP set top boxes, IP cameras, network storage, digitalvideo recorders, DVD players, hi-definition televisions, digital mediahubs, game consoles, IPTVs, etc.

Figure3. Applications for MCU with Non-PCI Ethernet Controller

Networking using a USB Host
Figure 4 depicts the configuration for microcontrollers with a built-inUSB host with either an internal or external USB to LAN controller,such as the eighth scenario in Figure1 . This configuration converts USB 2.0 to Fast Ethernet /Gigabit Ethernet in the embedded system through a cradle, portreplicator, or a docking station.

Because USB 2.0 only requires 4 pins, this allows the non-PCI bus todecrease the pin-count between the embedded system and the cradle ordocking station. An alternative configuration uses a built-in USB hostin combination with an external USB-to-LAN dongle to provide Ethernetaccess.

Figure4. Application Diagram of MCU with USB-to-LAN Controller

The rationale behind this configuration is simple: to take advantageof the USB's “plug-and-play” convenience and the 4-pin serial bus'shigh 480Mbps data transfer rate. This configuration is suitable forcomputer peripherals, handheld devices, home appliances, streamingmedia, multimedia networking, and consumer multimedia devices.

Figure 5 below depicts someof these devices, including USB Ethernet dongle, USB WiMAX card, UMPC(ultra-mobile PC), laptop docking station, cradles, digital recordersand players, DVD players, portable media players, IP set top boxes,game consoles, IPTV's and USB KVM Ethernet switches.

Figure5. Applications for MCU with USB-t0-Ethernet Controller

Single Chip MicrocontrollerNetworking
Figure 6 below depicts anembedded system that integrates the microcontroller, flash memory, andboth MAC and PHY layers in a single chip configuration with thesmallest form factor, as described in the first scenario depicted in Figure 1 .

This configuration is suitable for home appliances, industrial andhome automation, security systems, remote management, and streamingmedia applications such as POS devices, vending machines, IP cameras,Internet radio, automatic meter reading, environmental monitoringsystems, network sensors, networked UPS, serial to Ethernet adapters,and Ethernet ZigBee bridges.

Figure6. Network MCU Connecting Directly to the Internet

Satisfying the Market Demands forMiniaturization
Embedded system designers are frequently faced with the dilemma ofdesigning a remote management or communication device with higherspecifications and functionalities without increasing its form factor.Chip vendors have provided a variety of solutions to this dilemma, oneof which is by choosing a small package size.

Figure7. Embedded Ethernet Solutions

The 64-pin or TFBGA package depicted in Figure 7 above allows the Ethernetchip to be a quarter of the size of a US dime coin. An alternativesolution is to incorporate a higher degree of integration in a singlechip.

Figure 7 (right, bottom) depicts one such chip that integrates Ethernet MAC/PHY, TCP/IPaccelerator, and Flash memory into a single small form factor Ethernetmicrocontroller SoC.

The three scenarios described above offer alternative solutions toembedding Ethernet to satisfy the different needs for applicationdesigners today, whether they use a Non-PCI interface, USB interface,or Single-chip solution.

Jason Wang is director of Marketing at ASIX Electronics. He can be reachedat: jasonw@asix.com.tw. Harvey Jan is director of R&D at ASIX. Hecan be reached at: harvey@asix.com.tw

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