tech.am

Aus dem normalen Computer stammt die 3,5-Zoll große externe Festplatte. Die bietet aktuell bis zu 2 Terabyte (2000 GByte) Speicherplatz. Es gibt auch Gehäuse für externe Festplatten, in denen Platz für mehrere dieser HDs ist. So eine externe Festplatte bietet dann oft zusätzlich RAID 1 (höhere Geschwindigkeit bei der Datenübertragung) oder RAID 2 (mehr Datensicherheit durch Spiegelung auf zwei Festplatten). Angeschlossen wird so eine externe Festplatte über USB, Firewire, eSATA oder einen Netzwerk-Anschluss. Vorsicht: Bei manch einer externen Festplatte stört ein lärmender Lüfter.
Die kleineren Notebook-Festplatten sind 2,5-Zoll groß. Eine externe Festplatte mit 2,5-Zoll nimmt in den meisten Fällen über den USB-Anschluss Kontakt zum Computer auf und wird über dasselbe Kabel auch gleich mit Strom versorgt. Die geringen Abmessungen und das fehlende Netzteil machen 2,5-Zoll-Festplatten ideal für den mobilen Einsatz. Der Nachteil: Externe Festplatten mit 2,5 Zoll sind etwas langsamer als Ihre großen Brüder und bieten nur halb so viel Speicherkapazität (1 Terabyte). Noch kleiner sind die 1,8 Zoll großen Mini-Festplatten. Gerade mal scheckkartengroß pass so eine externe Festplatte in wirklich jede Tasche. Auch diese externen Festplatten werden über USB angeschlossen und benötigen keine extra Stromversorgung. Der Nachteil einer so winzigen externen Festplatte: Der Transfer großer Datenmengen dauert nochmal länger und mehr als 160 Gigabyte sind bei 1,8-Zoll-Festplatten nicht drin. Aber selbst das sollte für einen großen Teil der Daten reichen – die private Videosammlung einmal ausgenommen.

SSD als externe Festplatte

Ganz neu: Die mit Speicherbausteinen ausgestatteten Festplatten(SSD oder Solide State Disk). Sie sind unempfindlich gegen Stöße und Stürze, schnell, stromsparend und klein. Dafür ist der Preis leider noch etwas höher als bei externen Festplatten mit der alten Technik sich drehender Scheiben. In Zukunft wird diese stromsparende Technik bei externen Festplatten aber eine immer größere Rolle spielen.
Immer mehr Käufer legen sich eine externe Festplatte mit Audio- und Videoausgängen zu (Multimedia-Disks). Damit ist es möglich, Filme und Musik direkt von der Externen Festplatte auf dem Fernseher wiederzugeben. Und das dank HDMI und Full HD in ausgezeichneter Qualität.
Im Heimnetzwerk beliebt: Sogenannte NAS (Network Attached Storage). So eine externe Festplatte wird direkt an Ihren DSL-Router angeschlossen. So können Sie von jedem Computer im Netzwerk auf die externe Festplatte zugreifen, ohne das immer der Computer angeschaltet bleiben muss, an dem die externe Festplatte angeschlossen ist. Und bei Bedarf können Sie sogar über das Internet auf Ihre Daten zugreifen.
Externe Festplatten sind ausgereift, bekommen von den Herstellern wie Western Digital (WD), Freecom, Seagate und Lacie immer mehr Extras spendiert und erobern sich so immer neue Nischen und Anwendungsbereiche. So wird man auf seine externe Festplatte bald nicht mehr verzichten wollen und auch nicht verzichten können.

You probably have seen the video on YouTube about a molten Fonera, apparently due to overheating, which shows the plastic case completely deformed. Gizmodo (also in spanish) and other sites are also reporting on this. As usual, Fon has censored the post on their forums that broke the story, but alas, thanks to their partners at Google, here is a cached version. Even Martin Varsavsky seems worried about this. It seems the damage is obviously from heat, but could it have come from the Fonera itself?

I, and others, have our doubts about wether this video is a fake stunt, or a true story. It is true that the Fonera overheats, much more than would be expected from a consumer-electronics product, but to the point of causing physical damage to the plastic case?

The heat problem

Heat in electronics mostly comes from dropping voltage by converting current into it, in our case, the voltage regulator in the Fonera drops 5V to 3.3V at 500mA, resulting in the dissipation of 850mW. That’s right, we are dumping 850mW right into the atmosphere in the form of heat. This brings the operating conditions very close to the maximum ratings for this regulator, which has a maximum rated thermal resistance of 90ºC/W, my calculations put the operating conditions at 88ºC/W. Additionally, the wireless section of the Fonera is also converting a lot of energy into heat.

The measurements

After I finished my tests, I got a comment from Pobletewireless, regarding his own measurements of the heat problem, which are shown in very cool thermographs (no pun intended!) – much nicer than my rather rudimentary method.

I measured the temperature of the Fonera using a thermocouple connected to a Fluke 123 Scopemeter via an 80TK thermocouple module. The thermocouple was placed in between the heatsink and RF shield, the case closed, and the Fonera powered, as can be seen in this picture:

After 10 minutes operating normally, the temperature had risen to an average of 72ºC, with a peak of 80ºC.

The second batch of measurements were performed drilling four small holes to allow the thermocouple into the casing, the locations are shown in the following picture:

Maximum temperature at one corner was 43ºC. Next, an attempt was made to melt the white lid of the Fonera, by exposing it to a high temperature airflow from a paint-stripping gun, and at the same time, applying slight pressure from below. The thermocouple was used to measure at which point the plastic became maleable, and deformation started. At around 100ºC, the plastic was soft enough that a solid object could change its shape – this is in line with ABS plastic thermal properties, which state a deflection temperature around 100ºC, depending on specific material composition.

As the deflection point test resulted as expected, the lid was then exposed to an airflow at 280ºC for two minutes. The result of this exposure is shown in the pictures below:

It’s obvious that some deformation has taken place, with discoloration and charring on the point where heat was directly applied. However, the front side of the lid had mostly retained its shape.

Conclusions

The Fonera does indeed run very hot, much hotter than it should, if anything, for the good of the internal parts. Electronic components are sensitive to heat, with maximum ratings given by each manufacturer in terms of storage and operating conditions. The higher the temperature, the lower the service life of any given component. Some are affected more than others, most notably, electrolytic capacitors have a high sensitivity to heat, as it can evaporate the electrolyte quicker, causing it to fail. The capacitors in the Fonera are made by Taicon, a taiwanese manufacturer, and are max-rated for 105ºC. From the datasheet [PDF], at this temperature, the capacitor will fail after some 2000 hours, around 83 days. Following Arrhenius’ Law, and since the area around the capacitors was found to be at around 52ºC, their expected life would be 7800 hours, or about 325 days – what a coincidence, almost a full year, after which your warranty has expired. Comparing the Fonera to a Meraki Mini, one realises that there is a serious design flaw, as apart from the Mini having a switched-mode regulator, the wireless section shares exactly the same design as the Fonera. The temperature measured outside the casing of the wireless section indicates that the junction temperature of the components inside has to be ridiculously high. So, one conclusion is that the Foneras will eventually fail due to overheating, and it will probably happen sooner than later.

On the deformation / melting video – in my opinion, it’s not real. At least, it couldn’t have happened without the Fonera reaching temperatures around the whole casing that would have caused some components to blow up (for example, the capacitors). The Fonera could not have undergone such an extreme temperature, and still function as shown on the video. The temperature gradient between the heatsink and one corner of the case is almost 2:1, thus, to reach a deformation temperature of say 200ºC at the corner, the heatsink must have been running at 400ºC! A final bit of evidence – the sticker. If you look closely at the video, the sticker on the bottom of the Fonera looks almost unscathed. Here is a picture of what it looks like after applying a 250ºC airflow for 30 seconds, which causes the plastic to deform:

Obviously, a more prolongued exposure would have damaged it even more. In all honesty, I would love to get more details from the guy who made the video, as it stands right now, I’d call it a hoax.

I wrote before about the Logitech MX5000 Bluetooth keyboard & mouse combo, and there are plenty of posts around the web that confirm that the product sucks – badly.

To recap a bit, the problems are random reboots of the keyboard, disconnections of keyboard and mouse, erratic mouse behavior (including spontaneous motion of the cursor), and repeated keystrokes after the keyboard has not been used for a few minutes (resulting in things like “aaaaaaaafter the news…”). In all, a very frustrating and annoying experience, for a rather expensive combo. Logitech seem to acknowledge the problem, but I have not yet seen any form of update that could fix this, and my theory is that the problem cannot be fixed with a simple software update.

Declaring the keyboard and mouse defunct, I performed an autopsy, which revealed a few interesting facts (details after the jump):

• The Bluetooth dongle has a very very strange RF design – it uses a normal groundplane meander PCB antenna, but then it has a copper-wire loop antenna on top.
• Dongle and keyboard use Bluetooth chipsets from different manufacturers (CSR and Broadcom), in theory interoperable, in reality…well.
• The touchpad uses a very crappy sensor design, which explains the lack of responsiveness and uselesness of the scrolling controls.

Let’s start with the dongle. Below are a couple of photos of the opened device, the first with the loop antenna in place, the second with it removed, showing the meander. If someone with better RF knowledge than me can explain why this makes sense, I would be grateful. The design of the loop itself is wrong for 2.4GHz, having a wire length about 10 times larger than what would be required given its size.

The dongle uses a Broadcom BCM2045 chipset, with a 4Mbit flash memory onto which the firmware is loaded. The meander is a PCB track designed for 50ohm impedance, coupled to the chipset via a normal inductor-resistor-inductor matching network. Noticeable is the lack of baluns or filters, I’ll have to check the datasheet (if it’s publicly available) on this aspect.

Let’s take a look at the keyboard, starting with the touch controls. These are built into the keyboard as a separate module, linked to the main control board with a flat ribbon cable, and consist of three main pieces – the PCB and touch sensors, external case with printed cover, and a plastic support with built-in LED light pipes. The controls are made with a layer of gold-plated copper, printed on the underside of the PCB, and on the top side lives the control chip, made by Synaptics (who also makes touchpad systems and other stuff).

The principle by which these type of controls work is capacitance changes. When you place your finger near the sensor, a capacitive effect takes place (using the air and any other material in between as dielectric), which can be measured. It is very small, but enough to give an indication that a finger is present. There are a few rules that one must follow when designing such touchpads, as any interference in the capacitive effect can have negative results on the ‘feeling’ of the controls. Namely, ground planes have to be carefully controlled, and usually placed away from the sensor area, the sensors have to have a minimum size in order to be effective, and any trace routes from the sensor pad to the control IC have to be kept tight, avoiding cross-overs and other disturbances.

I am not familiar with the Synaptics chip, but I have worked with Quantum Research QProx devices, and I cannot see how the physics of capacitance could be avoided in either case. The MX5000 design violates all these rules. The sensor areas are irregular, with a gaping hole in the middle to allow for LED light to pass through, there are ground planes all over the PCB, the tracks meet and part at various spacings and passing right next to ground planes. The biggest joke seems to be the ’sliding’ sensors for the volume and zoom. These are depicted on the face of the keyboard as smooth analog paths, as if one could go from minimum zoom or volume to maximum by sliding the finger to each end of the vertical scale. The truth is that to change the volume in any significant way, one has to repeatedly slide the finger along the whole path of the scale several times, and in some cases, the detection doesn’t work. You end up looking demented, rubbing away the side of your keyboard repeatedly! As is shown on the photo, the sliding scale has only 7 distinct sensors, thus giving you a maximum of six detectable steps in either direction (each step is signaled by the triggering of one sensor, then the one adjacent, determining direction of finger travel). It would be a bad idea to place the whole volume or zoom range on a scale of six steps, and so they settled for the crazy-monkey-rubbing-keyboard action instead.

The next two pictures show the PCB inside the plastic assembly that houses the faceplate. Notice how the cutouts allow for light from the LEDs to be piped towards the labels and icons.

And finally, the last part of the broken equation – the Bluetooth module on the keyboard. It uses a CSR BlueCore3 ROM, which is cheap but cannot have its firmware modified after the die has been printed, meaning whatever bugs you had in the device will be there forever. Again, the module uses a meander antenna. Now, I am not too familiar with the Broadcom chipset, but I have worked with CSR chipsets quite a bit, and know they provide a balanced antenna output, this means that to use an antenna such as a meander or chip, you have to go through a balun. I don’t see a balun on the MX5000’s module, and so it appears they have attempted to balance the antenna with another set of meanders, which can be seen between the chip and the large main meander in the picture below:

Again, this design doesn’t seem to be the best in terms of RF performance, specially when you have a large inductor nearby (L1).

Conclusion? Don’t buy one of these, if you want to go wireless, get one of the non-Bluetooth (some also work at 2.4GHz) keyboard/mouse combinations, and I would still say get a Logitech, as they make some very good ones, such as the MX3000. I’ve always used Logitech, but the MX5000 has been a real lemon.

I got a tip today that Fon is looking at launching a new router with a LAN port, apart from the WAN port found in the current Fonera (they seem to privately admit not having a LAN passthrough was a rather big mistake).

With the current Fonera, you cannot access devices on the wired side of the network (such as a SAN drive or printer) from the wireless side, be it using the public or private SSID, you are effectively NATted from your own network. A LAN port would solve this the same way as it is done in higher quality devices such as the Linksys WRT54 series.

What really surprised me was to see that these routers have already been shown by Accton, the OEM that manufactures the Fonera on their website for a few weeks. Check out these links, datasheets in PDF available, for a white-label Fonera, a Fonera with LAN passthrough, and what looks to be the Fon Liberator, having a USB port and BitTorrent client built-in! Martin Varsavsky recently put the release date of the Liberator back a few months, originally scheduled for Christmas 2006, citing technical difficulties.

Now, either Accton wants to score a goal taking advantage of the publicity offered by Fon, or Fon didn’t pay an exclusivity fee for the design of these routers, or both. One million routers by 2010 is nothing by asian manufacturer standards, but they do allow buyers to secure exclusive designs. Copies could still be found, but not as prominently and by the same manufacturer making their own.

I wasn’t sure that Accton was the designer behind the Fonera, and gave Fon the benefit of the doubt of actually having developed something themselves in the electronics field, but now it seems clear that Accton is the designer of the hardware platfom, so there wasn’t that much development by Fon after all (the firmware was created by the hackers behind DD-WRT and OpenWRT).

It was only a matter of time until the developers of open-source firmware OpenWRT and DD-WRT managed to port the OS to the Fonera, which is based on an Atheros chipset. As described in this thread of the DD-WRT forums, there is a firmware package available for download, which can be flashed onto the Fonera, thus replacing FON’s original firmware and functionality. I think it will be a matter of time until we see reflashed Foneras on eBay, just like we saw Linksys once upon a time.

The hack is not for the faint-hearted, and so you risk bricking your router if the flashing fails – there is still a way to de-brick using the serial port, but in any case, don’t try this at home unless you know what you are doing. We are on the cutting edge of the development, which eventually trickles down into easier-to-follow HOWTOs and step-by-step guides.

The guys at Pobletewireless have been busy with the Fonera lately, and have now posted a step-by-step hack to add a DB9 connector that allows easy access to the built-in serial port, without having to make IDC cable headers and so on. [Link]

The hack gives access to the console, with which you can do all sorts of nice and interesting things.

Went to my local Vodafone store to pick up the new Huawei E220 HSDPA USB modem, which with a 49 Euro monthly contract gives you 1GB of transfer at 1Mbps maximum, and free mobile to fixed landline calls – pretty good deal if you ask me. For 59 Euro you get 5GB of transfer, at the full 3.8Mbps that HSDPA offers. These are theoretical rates, as they will depend on a number of factors, such as how many people are also using the same cell, your coverage and the quality of the link.
We can argue all we want about how convenient WiFi is, being omnipresent et al, but in reality, it’s rather hard to get connected while on the road. Let’s examine the following scenarios, and you tell me the chances of getting connected over WiFi:

• Riding the train or bus home.
• Getting a lift from a friend in his/her car.
• Opening your laptop at a random location (cafeteria, bar, etc. that you haven’t before scouted for open WiFi).
• On a plane, waiting for the next free takeoff slot that you hope the pilot won’t miss because he was checking the fatness of his wallet.

Let’s be honest – free open WiFi is great once you have identified the locations where you can get connected, such as a friend’s house or the local coffee shop. Other solid commercial alternatives make it easier to find WiFi, as they tend to be present at well-known locations. Walk into any Starbucks or hotel, and you’re bound to find at least for-pay wireless.
For me, on the 30 minutes to 1 hour it takes to get home on the train or bus, being able to get connected is great. The convenience of simply opening the Mac and getting online beats the guesswork of WiFi. I tried getting the Mac working with my Nokia N93 over Bluetooth, but it was just too unstable – one day it worked, the next simply refused to even connect. A more in-depth review of the device is coming, once I get a chance to roam about with it for a while.

So far, installation on the Mac was pretty straightforward, download the setup package from Vodafone’s site (they don’t tell you this in the manual), which then enables the modem as a networking device. If you don’t follow this step, it can get recognized as a storage device, which is not particularly useful for a modem. The one thing I don’t understand is why it comes with a miniUSB cable that ends in two USB connectors, my guess is it’s power-related (some USB ports don’t provide the full 500mA they are supposed to provide).

Yesterday, I posted a few pictures of the opened Fonera, with a few initial views on the device. When I tried to plug it in, it failed to work, only the power LED lighting up. Neither the WiFi signal was coming up, nor the ethernet port was tickling the switch.

The only course of action? To open it up even more. So, the aluminium chassis came off, and that’s when I realized I had seen this before. The WiFi section, which includes the Atheros AR2315, crystal, filters, power amplifiers and ancilliary circuitry are housed inside this casing, and correspond to a reference design provided most likely by Atheros themselves. Check out the Meraki Mini router. For reference, I provide a side-by-side picture below (click for large image).

This is further confirmed by looking closely at the Atheros website section on the AR2315, where we find the following picture:

There is nothing wrong with using reference designs per se, as it is the fastest and easiest way to bring a product to market. If you don’t need to customize your design much, simply use what the manufacturer suggests, and you will be playing on the safe side. A perfect example is Bluetooth headsets, where CSR dominates the market. Virtually all headsets in the market use their reference design, with very little changes between them, other than physical placement of LEDs and buttons.

Block-by-block, here is an overview of the Fonera.

Power

Power is supplied to the Fonera via jack SK1, and is fed through a rapid fuse (Polychem type) to a simple drop-down regulator, which drops voltage from around 5V (4.85V as measured on the wall power supply, using a Fluke 179 multimeter) to 3.3V. The regulator appears to be an AME1117 (though the package markings read AME117), in its CCCT configuration, TO-252 form factor. The regulator is stabilized using three electrolyic capacitors. In these types of regulators, ESR (equivalent series resistance) of the input decoupling capacitors is very important, and this can usually be controlled nicely with tantalum capacitors. These are very expensive compared to electrolytic, however.

There is a second stage of regulation, this time done by an Anpec APL1117, which further drops the voltage to 2.5V. This supply appears to be used by the wireless subsection. Two ceramic capacitors stabilize the regulator.

Without the Atheros chip in place, the PCB drew 90mA at 5V, or 450mW. Since the device was not functioning, the total supply current with WiFi active could not be determined.

Memory

Two memory ICs are available on the Fonera, the first is an ST M25P64 serial flash, with a 50MHz SPI bus and 64Mbit capacity (8MB), in 300mil SO16 format. The fact that SPI has been chosen has the advantage that extra memory devices could be attached to the bus, but it has the caveat that it is slower than a parallel bus. Thus, flashing a new firmware could take a rather long time. Interestingly, there are two footprints on the PCB, presumably to fit a different size and format memory IC, one SO16 and one SO8.
The second memory IC is a Hynix HY57V281620E synchronous DRAM, with a capacity of 128Mbit organized in 16bit blocks. In practice, this results in 16MB of RAM available to the processor.

Ethernet

At the heart of the wired ethernet subsystem is an Altima AC101 ethernet transceiver, capable of 10/100 full duplex operation. The IC is placed on the bottom layer of the PCB, and runs off a 25MHz crystal, strangely placed next to the main power regulator, where it could absorb electrical noise. Usually, crystals are placed well away from sources of interference. Nothing else too exciting here, the transceiver is connected to a standard RJ45 socket, TP1.

Wireless

The wireless section is the most interesting. This is where the Atheros AR2315 single-chip WiFi processor lives. Little public information is available about this or any other Atheros chipset, so it is hard to figure out exactly how it is put in place, but a few details are clear.

First, the chip gets hot. This is why a double heat-conductive adhesive tape bonds the surface to the metal cover, and in turn to the heatsink placed on top. The processor runs from a 40MHz clock source. After the Atheros core, come a couple of filters, and a power amplifier stage. This then runs off to the two antenna tracks. The first antenna exits the aluminium cage and runs up to a test connector. This connector breaks the antenna track when the right mating plug is inserted, which is then fed into a dedicated RF analyzer, which validates that the device is within constraints.

After the antenna test point, there is a split, which can be configured using a zero-ohm resistor, to run to an internal solder pad, or to a PCB-mounted right-angle SMA connector. It is unclear why they chose to use the solder pad, as an in-place soldered connector needs less handling than soldering a pigtail by hand. Besides, my intuition tells me the losses would be lower – I will test this when I get a working Fonera. Both tracks run through an impedance matching network, consisting of two capacitors to ground from the RF track, and an inductor between the capacitors . The purpose if this small circuit is to get the impedance of the PCB track as close to 50 ohms as possible. If the track impedance is mismatched to the antenna, losses take place.

The second antenna runs straight to a PCB pad, where a pigtail may be soldered, also passing a matching network. Below is a picture showing the details of this subsection.

Interfaces

There are two IDC-style connectors on the PCB, one 2×5, and one 2×7 but unpopulated. The 2×5 looks like a serial connector, as only power, ground and two tracks lead out from it. The layout has to be studied in more detail to confirm this assumption.
It can be speculated that this is in fact a serial port, but without the AR2315 pinout, this cannot be determined for sure. The 2×7 header seems to be a JTAG interface, possibly compliant with MIPS EJTAG 2.6. The mapping of the header pins to the AR2315 BGA balls is shown below (thanks for adding a row/column silkscreen for the Atheros chip, and thanks to the OpenWRT project wiki for the JTAG information!):

Between the Ethernet jack and the empty SMA footprint, there is a footprint of 6-way header, which needs a bit more study to determine where it leads internally [I will update the post when I find out –Mike].

Conclusion

This is a very compact and simple WiFi router, designed not for being easy to hack, but for lowest cost. The cheap power regulator, use of large SMDs and choice of pigtail rather than board-mounted SMA connector point in this direction. There is only one port which could be used for something useful, if it is indeed a serial port, the only two GPIOs available being the WLAN and Ethernet LEDs – as long as the Ethernet LED is not controlled by the Altima but by the Atheros. The power LED is on as long as there is power applied to the device, so there is no control over this by the Atheros processor. Power consumption is a bit high, considering the wireless device was not present. The PCB layout is very professional, except in a few particular cases such as the large crystal, but overall, quite nice.

In all, a very small device which could have a lot of potential, had it not been for its lack of I/O. It is unclear whether the router will accept custom firmware, as there are rumors that an encryption & signature system is used. The Fonera is probably OK for regular use by Foneros, but it does not have the hackable edge of the Linksys WRT54Gx. The only suprise could come from the edge connector, as of yet of unknown usefulness.

References

Atheros AR2315 chipset website section and product brief.

After a few days of silence, digesting the hubbub created by my analysis of Fon’s status, I’ve put my head back into more useful things than answering hate mail and out-of-line comments (thanks to those who provided balanced views, either for or against!). So, I decided to open a Fonera and see what lives inside.

A full review is coming, but first impressions:

• The plastic casing looks and feels very nice, the molds must have been expensive, as the different parts mate very well.
• Inside lives a single PCB, with components on both sides. The top holds the bulkier components, such as power regulator, RAM and WiFi section, inside an aluminium RF shield.
• The PCB looks professional and well laid out on first inspection.
• Components used (I haven’t opened the aluminium chassis yet) are older SOIC and TSSOP, thus cheaper to handle and solder. Balled components require from special handling, such as baking in hydrogen for 24 hours to dry them before soldering, etc.

Here are some pics (click each photo for bigger views on Flickr) I have taken with a Nokia N93 (really nice phone btw, mini-review coming):

The underside of the case, with screws off.

Perspective view of the top PCB.

Bottom side of the PCB.

Sticker on the flash IC showing the firmware version.