Tag Archives: teardown

Carlo Gavazzi EM210 coupled display panel teardown

The Carlo Gavazzi EM210 series [1] of 3 phase energy meters have a rather neat feature. You can mount them on a DIN rail or panel mount, with the same unit, and the display portion is simply detachable, and plugs back in on the reverse side. This is neat tech, and probably saves on inventory in a few distributor places at least, though I don’t imagine it makes any real difference for the end user, who will mount it once and leave it. Still, the display piece has the control buttons and the LCD display, no batteries, and no contacts. So I pulled it apart :)

I don’t know how it works really, it’s presumably the same method as NFC, by modulating the power draw from a capacitively or inductively coupled connection. It’s cool though. ATMega169 for the LCD control and buttons. Not entirely sure what the crystal is for, it’s marked “KDS3C” but I didn’t look further for a speed marking. Presumably you need a proper crystal to be able to synchronize the coupled connection properly? I don’t believe it’s an RTC crystal, as this is the detachable display portion. I always like seeing cutouts mid PCB for inserting big components.

The trimpot is an interesting idea. It’s used as a “lock”. With it turned all the way one way, the device is considered locked, and this screw access is on the back of the display portion. This portion also has tags for tamper seals, so I guess that’s one way of doing it on the cheap? Presumably just an ADC input to determine lock status.

The oddly slanted through hole parts on the left are the front panel buttons, nice alignment :)

ATMega169 for LCD control, coupled connection

ATMega169 for LCD control, coupled connection

[1] I’d link to them, but their website is junk and doesn’t let you link to products, and requires sign up to get a datasheet, that uses old names. The same sort of stupid games with redirecting you to different websites for different markets for the same device and all the usual terrible product management choices that lead engineers to ignore your products.

Minix NEO X5 mini – teardown and serial console

Well, I bought a “Minix NEO X5 mini” for various experiments, eventually planning just a plain linux server, with ethernet and wifi, and a pile more ram and flash than the regular OpenWRT router platforms. I chose this based mostly on the smallest, cheapest that had a physical ethernet port. The other contender was the UG008. (And UG008B) Those are marginally smaller, and have one less fullsize USB, also, I _thought_ I’d read good instructions on getting linux running on the x5mini, but it turned out the instructions were for the x5 (full size) which is very similar, but not the same. I’ve since found instructions for the ug008, maybe I should have bought that. It also has a power button and from the pcb pics, looks like the pads for test points are bigger. No heatsink though, and I’d heard it’s wifi wasn’t as good. (Rumous and hearsay, I’ve no idea really) The second fullsize USB port however, is kinda of interesting. The x5mini came with a rather unusual fullsize USB A male-male cable. And there’s no microusb port for the OTG like normal. Plugging this in to a regular pc host would be disastrous, so the supplied android has a special menu option to enable “connecting to pc” which resets on every boot. If you do have it turned on, and you push the pinhole on the bottom while plugging in the power, you’ll get a usb device that ADB can find. dodgy, a regular OTG port would have been preferable.

So yeah, it works pretty well out of the box, but there’s enough reviews of that. We’re here to pull it apart. The little screws are glued in, so you need a good screwdriver, I almost stripped them getting them out. Then, whee, brown PCB! And whee, they put a weight in it to feel pro ;)

The wifi (rtl8188es) antenna is soldered on, then soldered to an adhesive antenna on the lid, a little awkward, but perfectly reasonable of course. Immediately on the board you can see two missing ICs, one, labelled “WIFI2” is almost certainly Bluetooth, which is not on the x5mini, but is on the x5. More curious though is missing QFP48 IC by the recovery button, and it’s 12 pin “STM_DEBUG” connector. It certainly reminds me of an STM32 footprint, though the debug for cortex-m is normally 10 or 20 pins, not 12? No idea. Two test points on this side, T23 and T24, if it’s indeed a bluetooth module, this is possibly a uart between them? *shrugs*

Back to the “top” side, ethernet is an SMSC LAN8720A, power is a TI T659102, which seems to be pretty common on these boards. There’s two filled jumper blocks with interesting text, “USB1 Device / USB1 Host” and “Auto power on enable/disable” but I’ll leave them for a later time. There’s a rather unexpected battery connector too. Minix doesn’t have any battery backed devices in their catalog, so someone’s design company has been working on this. So much for thinking that minix was an OEM.

T306 is RX, T307 is TX and T308 is GND, for a serial console at 115200, 8N1


Finally, here’s most of the bootup