New Raspberry Pi PoE boards on oscilloscope

The new boards with protection diodes have arrived. After a quick soldering, we had a beautiful proto on our desk. https://www.flickr.com/photos/helsinkihacklab/17377299853/in/dateposted-public/

We tested the boards, full 100MBit/s speed was reached. The next test was to see if our clamping diodes work as they should, so it was oscilloscope o’clock.

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Before protection diodes

Syscomp CircuitGear3

After protection diode

The protection diode clamps the voltage spike to roughly 9 volts. Next thing to do was to plug the cable in and out ~100 times and see if the board would still connect. And connect it does! Now all that remains is to do a few cosmetic adjustments and launch the campaign.

Naming contest for our Raspberry Pi PoE board

As the board is getting ready for a launch, there is one big question remaining: How to name it? We cannot call it HAT, since our board doesn’t have ID EEPROM and it’s longer than the official specification. Most of us in ELL-i are engineering types and terrible at naming things, so we’re turning to You for help. Send your suggestions for the name of board to indie@ell-i.org by Friday 22.5, we’ll vote on the name in our upcoming Hackathon. There is a prize for winner: we’ll assemble one of the prototype boards by hand and send it to you anywhere in world where the Finnish mailman dares to go.

Also be sure to sign up in our mailing list here and we’ll send you a mail before the campaign launches so you can grab those early bird special deals.

 

 

Raspberry Pi PoE: Looking for testers

Our newest boards are currently in customs waiting to be cleared, they will arrive in time for our Hackathon next weekend.

We took this opportunity to make a few final adjustments to design. We added a connection for a pin header at the output before fuse in case someone wants to power some external load. To further help with external loads we also left a place for output voltage adjustment resistors so people can tweak the output to suit their needs.

We also pulled the DC/DC module a bit inwards to the board so it will have a bit more space between HiFiBerry DAC+ RCA-connector and DC/DC transformer.

new boards in mail

We’re going to launch the crowdfunding campaign soon. In meanwhile, if you want to receive one board ASAP we can send you the bare boards and parts at no markup. If you’re interested in assembling one board and giving it a try, contact us at indie@ell-i.org and we’ll arrange things from there.

Two steps forward, one backward

Last week we discovered that our PoE for Raspberry Pi eventually breaks the Ethernet port of connected Raspberry Pi. Since we have a few units which have been running constantly for almost two weeks, we started to suspect that the problem is in connection/disconnection transients. The first step was to find out if these connection/disconnections really were the cause of the problem, so we powered a Raspberry Pi separately and plugged the Ethernet connection a few tens of times. The Ethernet port of Pi stopped working quickly, and we had the isolated the cause of failure.

Time for some oscilloscope shots: the oscilloscope was connected on a differential pair after the transformer. Red and blue are differential wires, pink is the voltage differential between the two.

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This was one of the cleaner events on the cable, with only one clear spike on it. Our initial suspicions are confirmed, the ~57V on the unloaded PoE line gets coupled to the data lines. The recommended protection against these electrical transients is to add clamping diodes across the transformer pins. We had some suitable zener diodes lying around, so it was a quick matter of connecting them in antiseries and soldering them down on pins of the transformer.

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Time to take an another look with the oscilloscope. This time I caught a real monster of a cable transient on a tape:

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Even while the supply lines bounce around relative to ground, they stay nicely within 3 V swing relative to one another. This means that the attached Raspberry Pi should receive a lot less electrical stress from these events.

The attached Pi did survive a long series of cable connections, but it still could not form a link with the switch. On a hunch I forced the data rate down to 10 Mbit/s, and the Raspberry Pi was happy to communicate at that rate.

The degradation of speed down to 10Mbit/s is not acceptable, but hopefully this will not be a problem when we use lower-capacitance surface mount diodes close to transformer pins. There always is a option of using specialty ultra-fast, low capacitance transient voltage suppressor arrays if zeners seem to cause problems.

 

Raspberry Pi PoE prototypes: the Good, the Bad and the Ugly

Our new boards arrived, with the modifications made based on the feedback we received from previous prototypes. Board itself looks Good.

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On the flip side is the Ugly. 

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That bare metal ring? It should have been voided, as the other screw holes are. Oh well, it doesn’t degrade the functionality of the board, we just have to use plastic spacers with this one. Obviously we’ll fix it before the production.

The Bad was found from our previous prototype round. By now we have three broken Ethernet ports on Raspberry Pi’s. It seems that when the PoE cable is disconnected, there is a transient voltage spike in the data lines which gets coupled to Raspberry Pi and eventually destroys the Ethernet interface of circuit. This damage can be avoided by always disconnecting Ethernet cable to Raspberry Pi before disconnecting cable to PoE switch.

We obviously have to fix this issue before we launch the product. A protection scheme has already been designed and it will be prototyped on current design. This issue will not delay our campaign launch in May. We’ll be individually in contact with those of you who ordered a kit and ask if you want to have this version of the board or one with the transient protection a few weeks later.

We’re still waiting for a few of the higher quality parts, but of course we could not wait to test if it works as designed.

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The board works well, and it’s next task is to test the protection scheme. As we’re going to make another round of prototypes, option to buy kits is open! Contact us at Indie@ell-i.org and we’ll arrange things from there. We’ll sell the kits with no mark-up, but you’ll have to be skilled with soldering iron to assemble one. You can find earlier experiences of hand soldering the board from Vaasa Hacklab’s blog post. Be sure to sign up to our mailing list here and we’ll keep you updated of our progress.

Raspberry Pi 2 + Power over Ethernet + Owncloud + DD-WRT + Kodi + HiFiBerry DAC+ = Awesome media center

By now we know that our Raspberry Pi can be run with Power over Ethernet. Next question is: what to do with it? I’ve a little media center with TV, speakers and a blu-ray player back at my home, but I’ve not been satisfied with the ways to deliver content to it. Even if a smart T can play files automatically from my collection, given recent fiascos with smart TV’s and privacy I’m not willing to give one an Internet connection.

PC or laptop would feel like an overkill, so Raspberry Pi to the rescue! Last time I tried to run a media server with Raspberry Pi I was using model B. At the time the device was not powerful enough for the smooth experience, and I ended up donating it to my local hackerspace where it still serves as a IRC client. Let’s have another try with the new Raspberry Pi 2, as it is 6x faster, according to the box.

First thing was to plug the Power over Ethernet -board on it, so far so good. As the player software I selected Kodi, previously known as XBMC.  The steps to setup Raspberry Pi as a media PC is documented well enough around the internet, here for example. I already do have an ownCloud installation, which supports WebDAV file transfer. Kodi can be configured to access files over WebDAV, so I’m not limited by the 8GB of SD-card space anymore.

Next thing was to add a HiFiBerry DAC+ to Raspberry Pi for as good sound as possible. Setting it up was straightforward with the instructions found at their website, and I was ready to listen to the results. Everything worked… sorta. But there were a few user experience issues I wanted to correct. First of all, streaming media over WebDAV was laggy between songs. Maybe Raspberry Pi had to download entire song between playbacks? Anyway, this was simple enough to solve. Plug in USB-stick, download media locally to it and play from there.

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Final version of our board won’t have electric tape, no worries 🙂

Another issue was that I didn’t really want to go through the trouble of controlling the thing with keyboard and mouse. There are remote controls, but I’ve too many of those already. Kodi has a few web interfaces, I went for one known as Chorus. It allows me to control the Raspberry Pi through my LAN connection, so I can play music from my main speakers, adjust volume etc. Chorus also lets me to stream music to my local computer, in case I’m in another room and I don’t want to annoy my neighbours by turning the volume up.

At this point, I was pretty satisfied with the results. One more little thing, though. While I’m entirely happy to access my music by checking which IP was assigned to my Raspberry Pi by my router’s DHCP and entering something like 192.168.1.128:8080/ to my browser, my friends might not be that technologically oriented. My router runs DD-WRT, and it was pretty simple to assign a static IP-address and a hostname to my Raspberry Pi through the management interface of my router. Then there was the matter of routing the Kodi’s port 8080 to HTTP default port 80, but luckily I’ve done my fair share configuring Apache in the past.

Now I’m all set, all I have to do is to log into my home network, navigate to musiikki.a11 and enjoy.

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We still have a few sets of boards for the next round of prototypes available, so if you want to order one PoE boards + parts, contact us at Indie@ell-i.org and we’ll arrange things from there. We’ll sell them at cost, but you’ll have to be skilled with soldering iron to assemble one. You can find earlier experiences of hand soldering the board from Vaasa Hacklab’s blog post. Be sure to sign up to our mailing list here and we’ll keep you updated of our progress.

 

Raspberry Pi PoE: To pinch pennies or not to pinch pennies?

Good, cheap, small production run – pick two. That’s the question we’re facing this week. We have gotten some feedback about the pricing of our PoE HAT, two main viewpoints are:

1) It’s going to be expensive anyway, so at least it should have ALL the premium features

2) It absolutely must not be more expensive than the Raspberry Pi itself!

Unless we’re getting thousands of orders, we’re not going to split the product into “Economy” and “Premium” models. We would like to include:

  • Mounting hardware, as in 4 * board spacers.
  • Ethernet patch cables, which connect the HAT to Pi.
  • Long pins on pin header
  • High quality electrolytic capacitor on output
  • High quality input filtering for less radiated noise
  • Shielded ethernet connectors for more reliable data transmission

These are going to be stretch goals in our crowdfunding campaign.
Please let us know what you consider important by answering the survey here. Your answers help us to set the order of the stretch goals.

We’re also delighted to hear any suggestions for more features! Contact us at indie@ell-i.org with any comments and feedback.